research paper about weight training

Resistance training is medicine: effects of strength training on health

Affiliation.

• 1 Department of Exercise Science, Quincy College, Quincy, MA 02169, USA. [email protected]
• PMID: 22777332
• DOI: 10.1249/JSR.0b013e31825dabb8

Inactive adults experience a 3% to 8% loss of muscle mass per decade, accompanied by resting metabolic rate reduction and fat accumulation. Ten weeks of resistance training may increase lean weight by 1.4 kg, increase resting metabolic rate by 7%, and reduce fat weight by 1.8 kg. Benefits of resistance training include improved physical performance, movement control, walking speed, functional independence, cognitive abilities, and self-esteem. Resistance training may assist prevention and management of type 2 diabetes by decreasing visceral fat, reducing HbA1c, increasing the density of glucose transporter type 4, and improving insulin sensitivity. Resistance training may enhance cardiovascular health, by reducing resting blood pressure, decreasing low-density lipoprotein cholesterol and triglycerides, and increasing high-density lipoprotein cholesterol. Resistance training may promote bone development, with studies showing 1% to 3% increase in bone mineral density. Resistance training may be effective for reducing low back pain and easing discomfort associated with arthritis and fibromyalgia and has been shown to reverse specific aging factors in skeletal muscle.

• Aging / physiology*
• Health Status*
• Muscle, Skeletal / physiology*
• Physical Fitness / physiology*
• Resistance Training / methods*

• Systematic Review
• Open access
• Published: 31 January 2022

Effect of Different Types of Strength Training on Swimming Performance in Competitive Swimmers: A Systematic Review

• Line Fone 1 &
• Roland van den Tillaar   ORCID: orcid.org/0000-0002-4481-4490 1  

Sports Medicine - Open volume  8 , Article number:  19 ( 2022 ) Cite this article

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Strength training is widely used in swimming for improvement in performance. There are several ways to embark on strength training, which to different degrees follows the principle of specificity. There are disagreements in the literature on which training methods lead to the greatest performance improvements and to what degree resistance training must be specific to swimming to transfer to swimming performance.

The study was undertaken to examine (1) how different approaches to strength training for competitive swimmers can improve swimming performance and (2) which form of strength training resulted in the largest improvement in swimming performance.

A systematic review of the literature was undertaken using the following databases: PubMed, SPORTDiscus and Scopus. Studies were eligible if they met the following criteria: (1) a training intervention lasting longer than 3 weeks that investigates the effects strength training has on swimming performance, (2) involves youth or older experienced swimmers, (3) involves in-water specific resistance training, dry-land swim-like resistance training or non-specific dry-land strength training and (4) interventions with clear pre- and posttest results stated. Non-English language articles were excluded. Percent change and between-group effect size (ES) were calculated to compare the effects of different training interventions.

A range of studies investigating different strength training methods were examined. The percent change in performance and between-group ES were calculated; 27 studies met the inclusion criteria. The review revealed no clear consensus on which method of strength training was the most beneficial to swimming performance. All methods had intervention groups that increased their swimming performance.

Conclusions

This review shows that swimming differs from other sports as it is performed in water, and this demands a specific way of training. The results show that a combined swimming and strength training regimen seemed to have a better effect on swimming performance than a swim-only approach to training. Based on the principle of specificity and gains in swimming performance, there is not a clear conclusion, as the three main methods of strength training revealed similar gains in swimming performance of 2–2.5%.

This systematic review highlights the effects of different strength training forms on swimming performance.

In general, a combined swimming and strength training regimen is more effective than a swim-only approach to training to achieve gains in swimming performance.

It is not clear whether transfer of strength training follows the principle of specificity.

Introduction

Swimming as a competitive sport is popular worldwide and has been a part of the Olympic program since the first modern Olympic Games in 1896. Today, competitive swimming includes 16 Olympic pool events from 50 to 1500 m lasting from approximately 21 s to 15 min. Swimming differs from most other sports in several aspects, such as: (1) swimmers are in a prone, horizontal position during performance and training; (2) both arms and legs are used actively for propulsion; (3) water immersion causes pressure on the body and affects breathing; (4) aside from starts and turns, the forces from the athlete are at all times applied to a moving element; and (5) the equipment (e.g. swimming suit and cap) used during swimming has a minimal effect on swimming performance [ 1 ]. Nevertheless, swimming performance is determined by physiological, psychological and anatomical factors [ 2 , 3 , 4 , 5 , 6 ]. Barbosa et al. [ 7 ] specified that swimming performance depends on energetics, kinematics (the relationship between swim velocity [v], stroke length [SL] and stroke frequency [SF]) and kinetics (a swimmer creates work energy [kinetic energy] by propelling through the water). Loss of energy transfer is caused by inefficient movement, motor control (coordination of multiple segments at the same time to propel the swimmer forward), anthropometrics (e.g., body proportions, wingspan, body length and mass) and strength and conditioning. Many of these factors are hard, if not impossible, to change (e.g., body proportions and wingspan. Others are hard to investigate and measure (e.g., improvements in technique caused by better motor control). Therefore, this review will only discuss the relationship between strength and swimming performance. In these kinds of training interventions, it is easier to control the variables and get an accurate explanation for the changes in swimming performance.

Swimmers need great mechanical power output and muscular strength for good swimming performance [ 8 ]. Therefore, the ability to apply force in water is crucial in competitive swimming [ 9 , 10 , 11 , 12 ]. Upper body strength is essential in swimming for these propulsive forces and thereby swimming velocity [ 2 , 5 ]. Consequently, coaches and trainers use strength and conditioning programs to increase strength in athletes. Strength and conditioning (S&C) and dry-land training are common practices in swimming with the aim of enhancing swimming performance [ 7 , 13 , 14 ].

Many studies have examined the effects of strength and conditioning training on swimming performance, but the evidence that this form of training is beneficial for performance enhancement is not yet clarified in the literature. Some literature demonstrates a correlation between upper body strength and swimming performance [ 9 , 15 , 16 , 17 , 18 ]. Others have found a weak-moderate or nonsignificant correlation between strength and swimming performance [ 8 , 19 , 20 ]. Barbosa et al. [ 7 ] suggested that reasons for a weak relationship between dry-land strength and swimming performance are rooted in transfer issues between dry-land and aquatic-based strength (a lack in specificity). Furthermore, dry-land strength does not relate directly with swimming performance but indirectly through effects that dry-land strength training has on motor control, anthropometrics, biomechanics, etc.

Sadowski et al. [ 21 ] showed that the rate of transfer to swimming performance was significantly higher in a group that used a specialized ergometer for specific strength training as compared to that in a group that trained with traditional resistance exercises. Girold et al. [ 12 ], on the other hand, found that their traditional strength training group and the group that engaged specific strength training in the pool using resistance bands both gained similarly in swimming performance. Crowley et al. [ 22 ] performed a systematic review which explored the transfer of resistance-training modalities to swimming performance, and examined the effects of resistance training on technical aspects of swimming. They only reviewed fourteen studies of which ten were dryland resistance training and four swim-specific resistance-training methods at that time. The review concluded that low-volume, high-velocity/force, swim-specific resistance-training showed a positive transfer to swimming performance. However, the review [ 22 ] also identified that there is a lack of high-quality methodological studies at that time. Furthermore, they did not perform a systematic analysis of effect sizes and percentage of change in swimming performance between the studies. Therefore, the present study aims to review exercise training interventions to clarify what kind of strength training is beneficial for athletes to incorporate in their training routines for a gain in swimming performance. The focus of this review is to determine whether general dry-land strength training or swim-specific resistance training has the most transfer to swim performance in experienced competitive swimmers.

Literature Search

To find eligible literature for this review, an extensive search for exercise training intervention studies designed to improve swimming performance through different forms of strength training was conducted on the 30th of March 2021. The main databases utilized in this research were PubMed, Scopus and SPORTDiscus. In all databases, the main keywords were “swimming performance” and “strength training.” “Swimming” combined with “dry-land strength training,” “specific strength training” and “in-water strength training” were used as secondary searches. “Resistance training” and “weight training” were tried as a substitute for “strength training” in all databases. Complementary searches were done in Google Scholar. When systematic reviews, qualitative reviews and meta-analyses came up in the search that seemed relevant, a thorough screening of their references was conducted alongside a screening of eligible literature bibliographies and cross-references. When articles with a restricted full text online came up in the searches, they were requested and full access to them was gained. Figure  1 shows the complete searching process through a PRISMA flowchart.

A schematic representation of the searching process to find eligible studies for this review. A PRISMA flowchart was used to illustrate the inclusion and exclusion criteria used in this review

Inclusion and Exclusion Criteria

Only articles written in English were included in this review. Studies published before 1988 were excluded. A thorough screening of titles was conducted. Abstracts and articles written about other sports related to swimming (e.g., water polo, triathlon, open water swimmer and diving) were eliminated. Articles about sick, injured or paraplegic athletes and rehabilitation of patients related to swimming were also excluded. Studies applying supplements or any external manipulative intervention (e.g., wet suits, cold water immersion, electrical stimulation or altitude exposure), studies focus on tapering and recovery, studies surrounding respiratory training and correlation studies (e.g., stroke length and stroke rate; upper body strength and tethered swim force; or sprint performance and dry-land power) fell beyond the aim of this review and were excluded.

To get a relatively coherent pool of subjects, studies with young children, master swimmers and non-swimmers were also eliminated. This review will focus on competitive swimmers above the age of 13 and with a competitive level of at least a regional level. The subjects in this study are both male and female. Thirteen was set as the lowest age due to the uncertainty younger children represent in training interventions. Newer swimming training intervention studies with children have a tendency to report positive effects of the various strength training interventions [ 23 , 24 , 25 , 26 , 27 ], but it is difficult to determine if the swimming performance enhancement or decrement is due to the training interventions or factors such as maturation, physical growth, motivation, improvement in technique, psychological factors or a combination of several of these [ 28 ]. A mixture of male and female athletes was necessary to retrieve enough literature for this study, even though it could be argued that this, alongside the relatively wide age span of the participants, will compromise the accuracy of the results. Start and turn studies will not be covered in this review and were, therefore, eliminated from the search process.

To compare the effect of the different strength training interventions on swimming performance, the percentage of change in swimming performance was calculated together with the group effect size (ES) to determine whether the interventions have a real practical effect on the experimental groups compared to the control groups. The between-group ESs were sampled according to Cohen’s d \(\frac{Post\, CG-Post EG}{SD\, pooled}\) . ESs below 0.2 were defined as trivial effects, 0.2–0.5 small effects, 0.5–0.8 medium effects and 0.8–1.2 large effects. Furthermore, the ES of 1.2–2.0 was defined as a very large effect and ES above 2.0 as a huge effect.

General Findings

A total of 27 studies were eligible for the present review. To compare the effect of different methods of strength training on swimming performance, the 27 studies were divided into groups based on the specificity principle. They were constructed from the most specific to swimming to the least specific to swimming. In-water resistance training methods are the most specific, followed by dry-land swim-like resistance training and then the least specific dry-land resistance training methods, such as hypertrophy training, core training and maximal strength training. This categorization makes it possible to investigate if the most specific method to strength train has the largest transfer to swimming and leads to the largest gains in performance, thus following the principle of specificity.

From the 27 identified articles, 10 examined specific in-water resistance training with resistance bands [ 29 , 30 , 31 , 32 ], hand paddles [ 33 ], drag suit or parachute training [ 34 , 35 ], leg kicking training [ 36 ], arms-only training [ 37 ] and training with a specialized fixed push-off point (POP) device [ 38 ]. Four studies investigated swim-like specific dry-land resistance training [ 21 , 39 , 40 , 41 ], and 11 studies focused on non-specific dry-land strength training [ 8 , 9 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. Junior et al. [ 48 ] and Girold et al. [ 12 ] had two intervention groups and one control group, whereas one intervention group performed specific in-water resistance training and the other group performed non-specific dry-land strength training.

The included studies covered competitive swimming distances of 50 m or 50 yards, 100 m or 100 yards, 200 m and 400 m or 400 yards. Sadowski et al. [ 21 ] and Sadowski et al. [ 41 ] used 25 m sprints in their research. Most studies investigated the swimming style front crawl, but Mavridis et al. [ 31 ] investigated 50 m, 100 m and 200 m in the preferred style of the swimmer (an even distribution in all four swimming styles was applied in the study) and Naczk et al. [ 40 ] investigated both the 50 m front crawl and 100 m butterfly.

Most studies used, on average, 19.9 participants (range 10–37), except Mavridis et al. [ 31 ] who used 82 participants. The sex distribution was 345 men (66.6%) and 173 women (33.4%), with a total of 518 participants (not including Mavridis et al. [ 31 ]). The duration of training interventions ranged from 3 to 16 weeks, with an average of 8 weeks.

Results for Specific In-Water Resistance Training

Out of 12 studies with a specific in-water resistance intervention, 10 studies reported positive effects after the training intervention. Only Barbosa et al. [ 33 ], with a hand paddles intervention, and Dragunas et al. [ 34 ], with a drag suit intervention, showed no significant change in performance or stroke parameters pre- and post-intervention. Gourgoulis et al. [ 35 ], with a parachute intervention, on the other hand, showed a significant gain in the 50 m, 100 m and 200 m front crawl. Regarding swim performance, Girold et al. [ 32 ] reported only the resisted swimming groups showed a significant gain in 100 m performance. This was in line with Mavridis et al. [ 31 ] who found gains in 100 m and 200 m performance in the preferred swimming style. Girold et al. [ 12 ], with a combined resisted-assisted training group, found significant gain in the 50 m front crawl from pre- to posttest. Junior et al. [ 48 ] only showed significant improvements in the 25 m all-out sprint not in the 50 m performance. Kojima et al. [ 30 ] found significant gains in 50 m velocities in both the experimental and control groups after the participants followed the same sprint training program with and without resistance bands. Konstantaki and Winter [ 36 ] and Konstantaki et al. [ 37 ] with their leg kicking and arms-only swimming interventions did not find significant change in 400 m and 400 yards front crawl performance but found gains in submaximal oxygen uptake (VO 2 ), peak oxygen uptake (VO 2peak ) and exercise intensity at the ventilatory threshold. Papoti et al. [ 29 ], with tethered swimming, showed no significant gain in swim performance. The only significant gain was in peak blood lactate. Lastly, Toussaint and Vervoorn [ 38 ] used a MAD system (a system to measure active drag), which is a specialized POP device (fixed push-off points) that the swimmers used during in-water swimming training, to increase resistance in the drag phase of the front crawl stroke. They found a significant gain in the 50 m and 200 m front crawl. Unlike Girold et al. [ 32 ], Mavridis et al. [ 31 ] and Gourgoulis et al. [ 35 ] did not find a performance gain in the 100 m front crawl.

Specific In-Water Strength Training with Focus on the Arms

The interventions shown in Table 1 are specific in-water training interventions with added resistance on the arms in the form of hand paddles, arms-only swimming or the POP device (a fixed push-off point device in the water) of Toussaint and Vervoorn [ 38 ].

Specific In-Water Strength Training with Added Resistance

With this form of in-water strength training, the main goal is to increase the resistance so that the swimmer, in a very specific way, increases overall strength. The resistance band is attached to the swimmer’s waist and secured in the starting block. The swimmer swims out against the band and then maintains his or her position. In Girold et al. [ 32 ], there was one group that swam against the resistance and one that used the resistance band in the opposite way and decreased the total resistance. Most of the studies in Table 2 used resistance bands, but Dragunas et al. [ 34 ] used a drag suit, which is a swimming suit with added pockets around the waist that retains water and thereby increases the resistive drag force, resulting in the swimmer using more propulsive force to achieve the same result. The third way to increase resistance was to use a parachute [ 35 ]. The parachute was attached to the swimmer’s waist, and while the athlete swims, the parachute expands and creates a big surface. In the same way as the drag suit, this forced the swimmer to increase the propulsive force to attain the same velocity as when the swimmer does not use the parachute.

Specific In-water Strength Training with Focus on the Legs

Only Konstantaki and Winter [ 36 ] focused on increasing leg strength and performed a leg kicking study (Table 3 ).

Results from Specific Dry-land Swim-like Resistance Training

A swim bench is a way to perform specific resistance training out of the pool and is suggested to reproduce some elements of in-water swimming [ 16 , 39 ]. However, it cannot reproduce the aquatic feeling, which is specific to swimming and is an important component for a swimmer to master in regard to technique and swimming performance. When the swimmer uses the swim bench, he or she lies prone on a sliding bench with a slight incline, arms outstretched over his or her head and hands secured in hand paddles. The swimmer then pulls along the sliding bench and, therefore, mimics the kinematics of front crawl swimming. Sadowski et al. [ 21 ] and Sadowski et al. [ 41 ] used an ergometer like the swim bench. The ergometer was fastened to the end of the pool. When using the ergometer, the swimmer lies prone on a bench, similar to the position when performing the front crawl, while holding handles connected to a rotary head with blades located in the pool. When the swimmer uses the ergometer, it mimics the underwater phase of the front crawl stroke.

Results for Non-specific Dry-land Resistance Training

For non-specific dry-land resistance training, there was a large variance in the type of training undertaken by the athletes, what effects were measured, and the reported results of various interventions. Tanaka et al. [ 47 ] was the only study in this subgroup of training interventions that reported no positive effects after the training intervention, but Tanaka and colleagues were not alone in the lack of positive gains in swimming performance. Sawdon-Bea and Benson [ 45 ] and Schumann et al. [ 42 ] did not find significant changes in swimming performance. Junior et al. [ 48 ] found significant improvement in a separate 25 m all-out sprint but not in the 50 m front crawl performance. Trappe and Pearson [ 8 ] recorded a gain in swimming performance in both groups. In the experimental only group, they found a gain in maximal sprint swimming and maximal arm power in one of three methods utilizing the swim bench. In studies that reported gains in swimming performance, there was disagreement between studies as to which swimming distances were affected. Aspenes et al. [ 9 ] reported only significant improvements in the 400 m front crawl. Several studies reported improvements in the 50 m front crawl [ 12 , 43 , 44 , 49 , 51 ], while Lopes et al. [ 50 ] reported gains in both 50 m and 100 m performances. Potdevin et al. [ 46 ] reported improvements in 50 m and 400 m velocities.

Non-specific Dry-land Core Training

This form of training concentrates on increasing strength in the core muscles on the basis that a stronger core is beneficial to overcome the unstable and dynamic nature of the water and is necessary to produce and transfer force between the trunk and upper and lower extremities [ 52 ]. Swimming differs from other ground-based sports in that the core becomes the reference point for all movements [ 52 ]. The core muscles in these studies include the hip flexors, pelvis, trunk and shoulders.

Non-specific Dry-land Hypertrophy Training

Hypertrophy training is a training method to increase muscle mass, thereby increasing muscle strength. When using this training method, the athletes often train at 60–80% of 1RM and 6–15 repetitions for 3–5 sets. Junior et al. [ 48 ] and Lopes et al. [ 50 ] used a full-body training program, while Tanaka et al. [ 47 ] and Trappe and Pearson [ 8 ] utilized programs that were designed to increase strength in the upper body.

Non-specific Dry-land Maximal Strength Training

In maximal strength training, the athletes train with > 80% of 1RM with 1–6 repetitions for 3–5 sets, and the goal is to increase strength. Swimming is dependent on power and muscle strength [ 15 , 16 , 17 , 47 ], with the latter identified as a major component for success in swimming [ 8 ]. Strass [ 43 ] found that maximal strength training can change the rate of force development and maximal force. The gain in maximal force is influenced primarily by hypertrophy, while the explosive maximal force productions are affected by neural activation and are an important component of the underwater arm movement in sprint swimming.

Non-specific Dry-land Plyometric Training

Plyometric training is a way to train to enhance explosive strength. The improvement in strength originates from optimizing the stretch–shortening cycle, which occurs when the active muscle switches from rapid eccentric muscle action (deceleration) to rapid concentric muscle action (acceleration), therefore improving muscle function, coordination and the direction of the resultant force [ 53 ]. Normally explosive dry-land training in swimming is related to the performance of starts and turns [ 53 , 54 ], but Potdevin et al. [ 46 ] performed a study to see whether plyometric training influenced swimming velocity in the 50 m and 400 m front crawl.

Combined Strength and Endurance Training

Only one study [ 9 ] in this review performed a combined endurance and strength training intervention. The endurance component of the intervention consisted of 4 × 4 min high-intensity swimming at 90–95% of the swimmer’s maximal heart rate. The strength part of the training intervention consisted of maximal strength training on the latissimus dorsi, with maximal force in the concentric part of the movement and a slow eccentric phase [ 9 ].

Percent Change and Effect Sizes in Swimming Performance

In Fig.  2 , the percent changes in performance for the experimental groups are presented to compare the effects of different training interventions. Several of the interventions measured different swimming distances and are, therefore, represented individually. Girold et al. [ 32 ] had two experimental groups, one resisted and one assisted training group, so they are also represented individually. The results varied from a 7.5% positive response [ 35 ] to a negative response of 1.5% [ 47 ]. The only other negative response was Papoti et al. [ 29 ] in the 100 m front crawl (1.3%). Two experimental groups showed no percent change in swimming in the 400 m front crawl and 50 m front crawl performance [ 29 , 33 ]. The rest showed positive effects of their training interventions. The gains in performance were mostly in the range of 1% to 3% (Tables 4 , 5 , 6 , 7 , 8 , 9 ).

Percent change in swimming performance (s) after a training intervention

For the in-water arm strength training groups, the collective mean improvement was 1.7% (Table 10 ). The smallest improvement was 0% [ 33 ] and the largest improvement was 3.2% [ 38 ]. The in-water training interventions with added resistance had a 2.5 ± 1.9% mean performance improvement. There was only one specific in-water leg training intervention so there is not a collective mean, but the percent change for the one study was only 0.65% and not significant. For the swim-like dry-land resistance training groups, the mean improvement was 2.6 ± 1.9%. Lastly, we had non-specific dry-land strength training interventions. They were organized into subgroups. There was only one available plyometric training intervention and one intervention that combined endurance and strength training, so the mean improvement was based on the mean of the different swimming distances that the studies investigated. Collectively, the mean improvements of the plyometric trained group were 3.6 ± 0.8%. In the combined endurance and strength training group, the mean was 1.3 ± 0.2%. The core training interventions (1.9% improvement), hypertrophy training interventions (2.6% improvement) and maximal strength training interventions (2.7% improvement) all involved several studies. All the non-specific dry-land interventions had a collective mean change in performance of 2.5 ± 1.5%.

Most of the interventions did not reach medium ES. Three studies showed a medium ES between groups [ 12 , 21 , 40 ], while six studies revealed large ES [ 32 , 35 , 44 , 46 , 48 , 50 ] for the 100 m front crawl. Four studies showed very large ESs [ 12 , 40 , 49 , 50 ], while only two studies showed huge ESs [ 41 , 47 ] (Fig.  3 ).

Effect sizes (ESs) between the control and experimental groups

The main objectives of this review were to examine previous literature on (1) how different approaches to strength training for competitive swimmers can improve swimming performance and (2) which form of strength training resulted in the largest improvement in swimming performance. Collectively, almost all the experimental groups, and some of the control groups, showed a decrease in total swimming time and thereby gained a positive outcome of the training intervention. The results varied from a 7.5% performance increase [ 35 ] to a −1.45% performance decrease [ 47 ], with an average increase of 2.2% in the specific in-water training group, 2.5% in the non-specific dry-land strength training group and 2.6% in the dry-land swim-like training group. Furthermore, most of the studies were done in relation to the performance of the front crawl.

Method-Related Considerations

When assessing the results, there are important method-related inconsistencies that need to be considered. Firstly, there is a large age gap between the participants in the studies (13–24 years old), which leads to differences in competitive levels and training experiences that will influence the results. The highly skilled, older athlete with longer training experience has a smaller range of improvement than the younger more inexperienced athlete. Men were among the majority in the training groups (66.7%), and there was mixing of sexes in several of the groups. Some of the studies only had male participants [ 8 , 21 , 36 , 37 , 39 , 41 , 47 , 48 , 49 ]). Gourgoulis et al. [ 35 ] had young female participants and the rest of the studies had both male and female participants. Participants’ numbers ranged from 10 [ 8 ] to 82 [ 31 ], with an average of around 16 participants. Statistically, a low number of participants reduce the statistical impact of the study, and the value of the study’s findings must be evaluated accordingly.

Furthermore, there was a wide span in the duration of the training interventions. The shortest intervention lasted for 3 weeks [ 32 ] and the longest for 16 weeks [ 42 ], with an average of 8 weeks. This is problematic in the sense that the participants in the longer interventions had more time to adapt to the training, which could result in a more accurate representation of the effect that type of strength training had on swimming performance.

Another inconsistency is the three studies that did not apply a swim-only approach to their control groups [ 8 , 21 , 42 ]. These control groups performed their usual dry-land hypertrophy training, while their experimental groups performed dry-land swim-like strength training [ 21 ], maximal strength training [ 42 ] and weight-assisted hypertrophy training [ 8 ]. This makes it difficult to determine the effect of the training intervention as compared to that of a control group.

In-water Specific Resistance Training

Specific in-water arm strength training.

The interventions in this group were designed to increase arm strength through specific strength training in the water, and there were three eligible interventions. There were a hand paddle intervention [ 33 ], an arms-only intervention [ 37 ] and a POP device intervention [ 38 ]. It is difficult to conclude that this type of training has a definite positive or negative effect on swimming performance. Firstly, there is limited available research, since there are only three studies in this category. The mean of the three arm-strength interventions showed an improvement of 1.7 ± 1.2% (Table 10 ). However, Barbosa et al. [ 33 ] did not find a significant effect for their experimental group in a 50 m fc with 0% change in performance and a trivial change (0.14) between-group ES. This study was conducted over the span of only 4 weeks. This allows very little time for adaption to training and could explain the lack of results. Konstantaki et al. [ 37 ] also showed no significant improvement pre- and posttest in 372 m fc and a small improvement between-group ES. In this intervention, the EG performed 20% of the weekly swimming training with arms-only. The lack of improvement could be due to the fact that this form of training alone is not enough to gain more strength in the arms than normal swimming does. Although swimming performance did not improve, a 186 m arms-only trial did. This supports the principle of specificity. The EG improved the parameter they practiced, but there were transfer issues to swimming performance. Toussaint and Vervoorn [ 38 ] conducted tests on 50 m, 100 m and 200 m fc, whereas the experimental group showed a significant gain in all distances. The CG also showed gains in performance but only in the 100 m test. The ES was small. The device used in this intervention is highly specific to swimming and could be the reason that the EG improved their swimming performance. The CG performed the same sprint training as the EG but only showed a gain in the 100 m test, which could indicate that the chosen method of sprint training is effective, but the sprint training with the device was even more effective.

Specific In-water Resistance Training

In this group of training interventions, the focus is specific in-water training with added resistance. This is a swim-specific way to gain strength and follows the principle of specificity that specifies that training should be as close as possible to the actual sport performance. The resistance is applied to the swimmers through resistance bands, parachutes or drag suits. The mean percentage for this group was 2.5 ± 1.9% (Table 10 ), and all studies, except Papoti et al. [ 29 ], had a positive effect on swimming performance. This tells us that this method is likely to result in a positive gain in swimming performance. A 2.5% change in performance is a considerable improvement in competitive swimming, but the SD shows that the variation of improvement differs greatly between the swimmers.

Assessing the drag suit and parachute trained experimental groups’ performances, there are large differences in results, despite the fact that these training methods arguably are very similar. In Dragunas et al. [ 34 ], the swimmers pulled a parachute behind them, and in Gourgoulis et al. [ 35 ], they wore a belt around their waist with pockets that filled with water when the swimmers swam, increasing the resistance. Dragunas et al. [ 34 ] had a 0.3% gain in 50 m fc performance, while Gourgoulis et al. [ 35 ] experienced a 3.2%, 5.1% and 7.5% gain in 50 m, 100 m and 200 m tests, respectively. The between-group ES was trivial in Dragunas et al. [ 34 ], and in the 50 m, 100 m and 200 m tests in Gourgoulis et al. [ 35 ], it was small to large (0.32, 0.49 and 0.89, respectively). The large variance in results could be due to the fact that the swimmers in Dragunas et al. [ 34 ] were 19–20 years old, and in Gourgoulis et al. [ 35 ], the swimmers were only girls that were 13–14 years old. The younger athletes have a large potential for improvement and possibly have greater use of this form of strength training than the older athletes that are already much stronger. Furthermore, the Gourgoulis et al. [ 35 ] intervention lasted for 11 weeks, where as Dragunas et al. [ 34 ] intervention lasted for only 5 weeks. The 11-week intervention allows for more time for adaption to training and could explain some of the reasons that this intervention had better results than the 5-week intervention.

For the resistance band trained experimental groups, the results were more consistent. In the resistance band trained groups, there were two methods of using the resistance band. Most studies had the participants swim out with the band to give resistance [ 29 , 30 , 31 , 48 ]. The age of the participants ranged from 14 to 16 years old in all studies, and the mean gain in performance for the four interventions was about 2.0%. One study had a combined resisted-assisted method where the swimmers swam resisted one way and assisted the other way [ 12 ]. This resulted in a 3.0% gain in performance. Girold et al. [ 32 ] had two experimental groups, one group swam resisted, and one group swam assisted, and then compared the two. The resisted group had a 2.0% gain in performance, which correlated with the other four resisted trained groups, while the assisted group had a 0.9% gain in performance and the lowest gain in performance for all the resistance band trained groups. These results indicate that if training with a resistance band is desired, a combined resisted-assisted method might be most successful. However, only one study had this approach, which makes the results tentative.

Specific In-water Leg Training

The arms are generally considered the main propulsive factor in swimming and are, therefore, often the focus when discussing strength training in swimming, even though the legs contain large muscles with great strength potential. Aspenes and Karlsen [ 1 ] speculate the legs in swimming are more of a stabilization factor to reduce drag rather than increase propulsion and swimming velocity. Gullstrand and Holmer [ 55 ] performed a correlation study with international level swimmers over a 5-year period and found that tethered leg kicking was not related to swimming performance. On the other hand, Schumann and Rønnestad [ 56 ] mentioned that a gain in leg strength could result in improvement in start and turn performance, which could result in an all-over gain in swimming performance. Only one study was eligible for this review. Konstantaki and Winter [ 36 ] executed a leg kicking study but found no significant change in a 400 m fc (-0.65%). The between-group ES was small (0.2). Arguably, a 0.65% gain in performance for an experienced swimmer is a positive effect, but considering the distance swam (400 m fc), this result is not of any real practical importance. Due to the limited availability of research, it was not possible to draw a definite conclusion of how an in-water leg training intervention could affect swimming performance. Compared to the in-water arm-strength training and the in-water resistance training, it seemingly would be beneficial to perform these methods of resistance training over the in-water leg training.

Dry-Land Swim-Like Resistance Training

This form of strength training is considered the most specific to swimming, when on dry land. It mimics the swimming performance, but it lacks specificity in the sense that the arms are isolated, the drag phase is longer than a swimming stroke in the water, and the distribution of the drag forces at various joint angles is not like in-water swimming [ 57 ]. It is also worth considering that this form of training demands specialized equipment that may not be as accessible as a swimming pool, rubber bands or a strength training room.

The collective mean for these intervention groups was a 2.6 ± 1.9% enhancement in performance, but there were large differences in performance changes. The greatest change was in the Roberts et al. [ 39 ] study on 91.44 m fc, with a 5.0% increase in performance. However, this is probably not due to the swim bench training, as the CG also experienced large and almost the same gain in performance (5.1%) over the 10-week intervention. This could mean that other substantial factors have impacted the swimmers, as a 5% improvement is a huge enhancement in 91.44 m. Roberts et al. [ 39 ] speculated whether the improvements could be due to the fact that earlier in the season the main goal was to improve the biomechanics of the stroke and maximal VO 2, while in the second part of the season, when the intervention took place, the focus shifted to a more high stroke turn over, anaerobic power and endurance, which are all important factors in a 91.44 m performance. The shift in focus obviously had a positive impact on the swimmer’s performance, but it is not certain that the swim bench training had an extra positive effect compared to the CG. Naczk et al. [ 40 ] used the same swim bench method as Roberts et al. [ 39 ] but found significant changes in the 50 m fc and 100 m butterfly (0.79% and 1.83%, respectively) in the EG only. However, Naczk et al. [ 40 ] also had limitations, as the duration of the intervention was relatively short (4 weeks). This provided little time to adapt to the training, making the findings uncertain. Naczk et al. [ 40 ] believed that some of the effects could be explained on the basis of placebo.

Sadowski et al. [ 41 ] and Sadowski et al. [ 21 ] used a device similar to the swim bench called a hydro-isokinetic ergometer. Sadowski et al. [ 41 ] performed a 6-week intervention and found a nonsignificant 1.2% gain in performance in the EG, while Sadowski et al. [ 21 ] performed a 12-week intervention and the EG had a significant 4.1% change in performance (as did the CG) (2.7%). The control group did not perform a swim-only method, but rather dry-land hypertrophy training. This made it difficult to ascertain the true effect of the ergometer vs. normal swimming practice, but it made it possible to compare swim-specific dry-land training and non-specific strength training. Both methods resulted in significant gains in performance, but the swim-specific method had greater improvements than traditional strength training. When comparing the two ergometer trained experimental groups, Sadowski et al. [ 21 ] showed the largest performance enhancement compared to Sadowski et al. [ 41 ], which was probably due to the duration of the interventions (12 weeks vs. 6 weeks).

Dry-land Non-specific Resistance Training

Core training.

This type of training is non-specific to swimming, but it is widely used by swimmers due to the unstable nature of water, which demands a strong core for a purposively forward propulsion. The collective mean change in this group was 1.9 ± 0.8%, all measured in the 50 m fc (Table 10 ), which is a substantial improvement in such a short distance for experienced swimmers. However, Sawdon-Bea and Benson [ 45 ] indicated an insignificant change in performance for the EG of 1.7%, which was hard to explain. Some possible reasoning for the absence of a significant increase in performance probably lies in the fact that the participants were only experienced high school swimmers competing at a regional level, which could have affected the quality of core training they received due to variations in levels between the participants at this level. Furthermore, Sawdon-Bea and Benson [ 45 ] did not specify what kind of core exercises the participants executed. The exercises could lack an element of specificity that the other interventions had and therefore, was not always transferred to the swimming performance for each participant.

Traditional Resistance Training

Traditional resistance training is widely used in swimming and involves conventional gym-based strength training. In this review, traditional resistance training was divided into hypertrophy training, maximal strength training, plyometric training and a combined endurance and strength training regimen. The mean change in performance for these methods was 2.6 ± 1.5%, with only one study reporting a negative outcome in swimming performance [ 47 ]. This was a hypertrophy training intervention with a focus on upper body strength. The EG in a study by Tanaka et al. [ 47 ] increased their weights by 25–35% over the span of the intervention but showed no gain in swimming performance or swim bench power. The lack of positive transfer could be due to a lack of specificity in the training. This may be an insufficient explanation for the decrease in performance, while the mean gain in performance in the hypertrophy trained groups was 2.6%. Trappe and Pearson [ 8 ] applied a weight-assisted hypertrophy strength training program for the EG, while the CG performed free-weight hypertrophy training. This made it problematic to investigate the differences between a combined hypertrophy and swimming training regimen and swimming training alone. Both the weight-assisted group and free-weight group gained significant change in the 365.8 m fc (around 3.8% for both groups) and had a trivial (0.03) between-group ES, which tells us that there is little difference between the two training methods.

It does not appear to be of importance whether the hypertrophy training was full body or upper body focused, as similar improvements were found after performing a full body strength training routine rather than an upper body focused one [ 21 , 42 , 48 , 50 ]. This strays from the principle of specificity that says the upper body is the primary propulsion factor in swimming and that it seemingly would be most beneficial to perform upper body strength training. However, this is in line with the in-water resistance training groups where the added resistance trained group gained larger performance enhancements than the in-water arm strength only training group. This could mean that a full body focused resistance training regimen, regardless of whether it is in-water or on dry-land, is more beneficial to the transfer to swimming performance rather than just focusing on one part of the body (e.g., the arms).

In the maximal strength training interventions, the collective mean was 2.7 ± 0.8%, which states a possible likelihood of change in performance. Most studies conducted only the maximal strength training intervention and compared it with a control group, which gives a clear indication if the strength training has a positive effect or not. Only Aspenes et al. [ 9 ] conducted a study where they combined a 4 × 4 min endurance program and maximal strength training (a pull-down exercise designed to mimic the butterfly stroke). They investigated the 50 m, 100 m and 400 m freestyle, and the mean change in performance in the three distances was 1.3%. The only significant changes were found in the 400 m performance. The between-group ES never reached a significant level, except in the 100 m performance, with a small between-group ES (0.46). Therefore, in this study, it is difficult to predict whether the gain in the 400 m performance is due to the maximal strength training or to the endurance training, but it is suggested to be related to the strength portion of the program since the VO 2max and work economy remained unchanged [ 9 ]. Aspenes et al. [ 9 ] was the only study that tried to apply a specificity aspect to maximal strength training. This seemingly did not make a difference in the swimming performance, as the other maximal strength training groups had larger improvements in performance (2–3%). This may indicate that a general increase in strength is sufficient and preferred for an improved swimming performance.

Only one study investigated the effect of plyometric training on total swimming performance [ 46 ]. Plyometric studies in swimming are often related to start-and-turn performance and Bishop et al. [ 54 ] showed positive effects in swimming performance after this kind of training. Potdevin et al. [ 46 ] showed a 3.1% and 4.7% change in the 50 m and 400 m fc, respectively, which is a considerable improvement. The CG also significantly improved their 400 m performance (1.1%), which makes it unclear if it is the strength training intervention or other factors that influenced the swimmer’s performance. Nevertheless, the gain in performance was larger in the EG, which tells us that maybe plyometric training had a positive effect. In the 50 m performance, only the EG improved their performance. This could be due to the shorter distance, where start performance plays a greater role in total performance than in the 400 m, and plyometrics has been shown to positively affect start performance [ 54 ]. However, one study is not enough to conclude whether plyometric dry-land training has a positive or negative effect on swimming performance.

Comparison of Training Methods

It is an established fact that specificity in training is necessary for positive transfer to performance, but it is curious to note that all three groups had a mean gain in performance of 2–3%, which is a considerable improvement for competitive swimmers, regardless of what kind of strength training they performed. Regarding mean gain in performance, specific in-water training methods had a 2.2% mean gain, dry-land swim-like resistance training had a 2.6% mean gain, and dry-land non-specific strength training had a 2.4% mean gain. Thereby, the current literature demonstrates that various resistance training methods can positively impact swimming performance.

Dry-land swim-like resistance training showed the greatest change in performance, but this is also the group with the fewest studies and participants. Only one of four studies showed a statistically significant change in performance, which could be due to the lack of specificity in the movement of the swim bench. The non-specific dry-land training methods were used in 13 different studies. Three subgroups contained several interventions and made it possible to draw the following conclusions: (1) core training showed a 1.9% gain in performance, (2) hypertrophy training a 2.6% gain and (3) maximal strength training a 2.7% gain, which showed that all methods could positively affect swimming performance. Core training could be beneficial due to the nature of swimming, but it needs to be specific in the way that the core training on land is transferable to in-water swimming. Both hypertrophy and maximal strength training led to similar and considerable gains in swimming performance, which indicates that gain in muscle strength, even though the training is not specific to swimming, is transferable to swimming and has positive effects on performance. These methods showed substantially larger effects than core training, which might predict that hypertrophy or maximal strength training could be more useful to the swimmer than core training alone. Specific in-water training with 12 included studies had the least gain in performance. Nevertheless, the results showed that specific in-water strength training also leads to a probable gain in performance. The greatest all-over individual swimming performance improvements were found in this group. Within this group, the interventions with added resistance had greater gains in performance compared to the arms and legs focused interventions, which could be due to the principle of specificity. The act of swimming with a rubber band is more specific to swimming than swimming only using the arms.

When discussing the principle of specificity, it would be reasonable to conclude that the specific in-water training should lead to a greater gain in performance. There could be several reasons for this outcome, and due to the limited availability of literature, it is hard to make a definite conclusion. One reason may be that dry-land hypertrophy and maximal strength training leads to greater improvement in muscle strength than in-water resistance training and that might be what is needed to significantly increase swimming performance. It has been shown that younger athletes benefit from in-water resistance training [ 30 , 31 , 35 ], but for stronger and more experienced swimmers, in-water resistance does not necessarily result in increased muscle strength, which could be why dry-land strength training is more effective for improvement in swimming performance.

This review has three limitations. First, as there are limited studies in some of the categories it is still not possible to provide a definitive statement about which resistance training method is the most effective one to increase swimming performance. Secondly, it is possible that some studies were not found in the search process. Lastly, there are many other factors that could influence swimming performance over time which are possible confounding variables outside of the intervention programs since training is a multifactorial process.

The main finding of the review was that all three main training method groups had interventions that led to significant gains in front crawl swimming performance. While the change in performance ranged from −1.45 to 7.5%, the majority of the interventions led to a 2–3% gain in performance. It seems that dry-land swim-like resistance training, hypertrophy training and maximal strength training are the most successful strength training methods to increase swimming performance, especially for more experienced and stronger senior competitive swimmers. Thus, for coaches and swimmers, we suggest including these training methods in the training regime. However, the findings did not follow the principle of specificity that specific in-water strength training is more beneficial to swimming performance than non-specific resistance training. It must not be construed that dry-land strength training can replace specific swimming training, but it might be a positive addition to the training program. It is clear that any of the different resistance training methods led to greater gains in swimming performance compared to the control groups where the subjects had a swim-only approach to training. Further research with high-quality randomized controlled trials and longer training interventions with full documentation of all training plans using elite senior swimmers are necessary to accurately interpret the results of the various forms of strength training and to provide guidelines for resistance training for swimmers.

Availability of Data and Materials

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Abbreviations

1 Repetition maximum

Bench press

Control group

Countermovement jump

Dry-land strength training

Experimental group

• Effect size

Front crawl

Ratings of perceived exertion with Borg’s scale

Swimming force

Stroke length

Stroke rate

Swimming velocity

Oxygen uptake

Maximal oxygen uptake

Ventilatory threshold

Weight-assisted group

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Fone, L., van den Tillaar, R. Effect of Different Types of Strength Training on Swimming Performance in Competitive Swimmers: A Systematic Review. Sports Med - Open 8 , 19 (2022). https://doi.org/10.1186/s40798-022-00410-5

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Weight Training: Principles and Recommendations Research Paper

Introduction, principles of weight training, works citied.

Weight training is a form of organized body exercise in which the body muscles are made to shrink and contract to stimulate growth and strength. It can also be termed as an exercise that uses weights and machines to create resistance to the muscles by having a variety of movements. It capitalizes on the increasing workload on the muscles.

Type of lift: The lift should be chosen by considering the body part a person needs to strengthen. Various body parts will have different types of lifts.

Intensity: This refers to the effort that is necessary for a workout. For example, reducing the resting time between sets and having supersets.

Volume: This refers to the duration and the number of workouts a person undergoes. It can be determined by the number of days trained in a week and the duration of the sessions.

Variety: It is achieved through changing workout programs. It involves having a variety of exercises in a workout.

Progressive overload: The weight should be increased gradually and systematically to enhance the growth of muscles. Rest: A trainee needs to have breaks between sets. The duration of these breaks is usually determined by the goals of the trainee. For example, if one’s objective is to increase the size of the muscles, less rest between the sets is recommended than when the objective is to strengthen them.

Recovery: After workouts, the trainee needs to rest the muscles to give them room to repair and grow. At least 48 hours are recommended. Benefits of weight training: Toning of muscles: Weight training helps in toning muscles for them to look good and also helps in raising the basal metabolic rate. Strengthening bones: Weight training helps in the strengthening of bones and in maintaining bone density. As we get old, we tend to lose bone density especially women who lose about 1% to 2% of the total bone density especially after menopause. A combination of a good diet and exercise can help in muscle building and strengthening of the tendons thus reducing the risks of getting osteoporosis. Enhancing flexibility and balance: Weight training helps in energizing the body by strengthening the joints and muscles to work more efficiently together to give much-desired balance, flexibility, and increasing resistance to injuries.

It can also help in lessening the joint pains especially the lower back pains as well as improving motion, especially in older people. The increase in balance is more beneficial to older people as it prevents them from falling. Benefits of weight training to the cardiovascular system: Training or exercising with light weights and more frequently for example 12 to 15 times, benefits the heart. This can also be beneficial to many older people (Neipris 4).

Weight management: Weight training increases the metabolic rate and therefore burning fat. Weight training combined with cardiovascular workouts revitalizes metabolism by adding muscle mass.

Chronic illness management: Training helps in controlling blood sugar. Studies show that it helps people with diabetes especially diabetes type two to keep blood sugar in the normal range (Neipris 4). Strength training can also be used with cancer patients especially during their chemotherapy period. It has been known to be useful in maintaining lean mass and enhancing fitness especially in prostate cancer patients (Rogers 2). The training can also be of help in improving mobility to patients who have Parkinson’s disease especially eccentric resistance training (Rogers 2). Arthritis patients can also benefit from strength training through well-defined resistance training programs. Play better and safe: Weight training makes the muscles stronger especially in body parts that are prone to injury such as the lower back. The knee for instance becomes stronger when the runner exercises during off days. Strength training helps people feel better and positive and may even help in reducing depression levels. The improved strength and physique mostly increase self-esteem and confidence (Neipris 7). It can also help in improving sleep as people who tend to weight train sleep quicker and deeper.

Posture: This refers to the way we sit or stand which is greatly influenced by the status of the neck, shoulders, back, hip, and abdominal muscle (Walker 7). Stronger muscles help in standing and sitting comfortably.

Only safe and well-maintained equipment should be used for weight training. The use of Faulty equipment and machines will greatly increase the chances of being injured. Warming up and cooling down should be emphasized before and after exercises. Stretches should be incorporated. Appropriate clothing should be worn during training preferably natural fibers. Exhaling during strenuous exercise is recommended rather than holding a breath. Correct weight lifting techniques should be applied because the wrong usage of these techniques will lead to slow progress or even cause injuries. Always consult with a qualified gym instructor or physiotherapist in case of any doubts. Ensure that the weights are moved through the joints’ full range of motion. This helps in working the muscles fully and lowers the chances of getting joint injuries (Walker 8).

Neipris, Louis. 8 Health Benefits of strength training. My Optum health.com. 2008. Web.

Rogers, Paul. Health and Fitness Benefits of Weight Training. About.com. 2008. Web.

Walker, Doug. The Benefits of Strength Training . The training station. 2001. Web.

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IvyPanda. (2021, November 21). Weight Training: Principles and Recommendations. https://ivypanda.com/essays/weight-training-principles-and-recommendations/

"Weight Training: Principles and Recommendations." IvyPanda , 21 Nov. 2021, ivypanda.com/essays/weight-training-principles-and-recommendations/.

IvyPanda . (2021) 'Weight Training: Principles and Recommendations'. 21 November.

IvyPanda . 2021. "Weight Training: Principles and Recommendations." November 21, 2021. https://ivypanda.com/essays/weight-training-principles-and-recommendations/.

1. IvyPanda . "Weight Training: Principles and Recommendations." November 21, 2021. https://ivypanda.com/essays/weight-training-principles-and-recommendations/.

Bibliography

IvyPanda . "Weight Training: Principles and Recommendations." November 21, 2021. https://ivypanda.com/essays/weight-training-principles-and-recommendations/.

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How can I plan what to eat or drink when I have diabetes?

How can physical activity help manage my diabetes, what can i do to reach or maintain a healthy weight, should i quit smoking, how can i take care of my mental health, clinical trials for healthy living with diabetes.

Healthy living is a way to manage diabetes . To have a healthy lifestyle, take steps now to plan healthy meals and snacks, do physical activities, get enough sleep, and quit smoking or using tobacco products.

Healthy living may help keep your body’s blood pressure , cholesterol , and blood glucose level, also called blood sugar level, in the range your primary health care professional recommends. Your primary health care professional may be a doctor, a physician assistant, or a nurse practitioner. Healthy living may also help prevent or delay health problems  from diabetes that can affect your heart, kidneys, eyes, brain, and other parts of your body.

Making lifestyle changes can be hard, but starting with small changes and building from there may benefit your health. You may want to get help from family, loved ones, friends, and other trusted people in your community. You can also get information from your health care professionals.

What you choose to eat, how much you eat, and when you eat are parts of a meal plan. Having healthy foods and drinks can help keep your blood glucose, blood pressure, and cholesterol levels in the ranges your health care professional recommends. If you have overweight or obesity, a healthy meal plan—along with regular physical activity, getting enough sleep, and other healthy behaviors—may help you reach and maintain a healthy weight. In some cases, health care professionals may also recommend diabetes medicines that may help you lose weight, or weight-loss surgery, also called metabolic and bariatric surgery.

Choose healthy foods and drinks

There is no right or wrong way to choose healthy foods and drinks that may help manage your diabetes. Healthy meal plans for people who have diabetes may include

• dairy or plant-based dairy products
• nonstarchy vegetables
• protein foods
• whole grains

Try to choose foods that include nutrients such as vitamins, calcium , fiber , and healthy fats . Also try to choose drinks with little or no added sugar , such as tap or bottled water, low-fat or non-fat milk, and unsweetened tea, coffee, or sparkling water.

Try to plan meals and snacks that have fewer

• foods high in saturated fat
• foods high in sodium, a mineral found in salt
• sugary foods , such as cookies and cakes, and sweet drinks, such as soda, juice, flavored coffee, and sports drinks

Your body turns carbohydrates , or carbs, from food into glucose, which can raise your blood glucose level. Some fruits, beans, and starchy vegetables—such as potatoes and corn—have more carbs than other foods. Keep carbs in mind when planning your meals.

You should also limit how much alcohol you drink. If you take insulin  or certain diabetes medicines , drinking alcohol can make your blood glucose level drop too low, which is called hypoglycemia . If you do drink alcohol, be sure to eat food when you drink and remember to check your blood glucose level after drinking. Talk with your health care team about your alcohol-drinking habits.

Find the best times to eat or drink

Talk with your health care professional or health care team about when you should eat or drink. The best time to have meals and snacks may depend on

• what medicines you take for diabetes
• what your level of physical activity or your work schedule is
• whether you have other health conditions or diseases

Ask your health care team if you should eat before, during, or after physical activity. Some diabetes medicines, such as sulfonylureas  or insulin, may make your blood glucose level drop too low during exercise or if you skip or delay a meal.

Plan how much to eat or drink

You may worry that having diabetes means giving up foods and drinks you enjoy. The good news is you can still have your favorite foods and drinks, but you might need to have them in smaller portions  or enjoy them less often.

For people who have diabetes, carb counting and the plate method are two common ways to plan how much to eat or drink. Talk with your health care professional or health care team to find a method that works for you.

Carb counting

Carbohydrate counting , or carb counting, means planning and keeping track of the amount of carbs you eat and drink in each meal or snack. Not all people with diabetes need to count carbs. However, if you take insulin, counting carbs can help you know how much insulin to take.

Plate method

The plate method helps you control portion sizes  without counting and measuring. This method divides a 9-inch plate into the following three sections to help you choose the types and amounts of foods to eat for each meal.

• Nonstarchy vegetables—such as leafy greens, peppers, carrots, or green beans—should make up half of your plate.
• Carb foods that are high in fiber—such as brown rice, whole grains, beans, or fruits—should make up one-quarter of your plate.
• Protein foods—such as lean meats, fish, dairy, or tofu or other soy products—should make up one quarter of your plate.

If you are not taking insulin, you may not need to count carbs when using the plate method.

Work with your health care team to create a meal plan that works for you. You may want to have a diabetes educator  or a registered dietitian  on your team. A registered dietitian can provide medical nutrition therapy , which includes counseling to help you create and follow a meal plan. Your health care team may be able to recommend other resources, such as a healthy lifestyle coach, to help you with making changes. Ask your health care team or your insurance company if your benefits include medical nutrition therapy or other diabetes care resources.

Talk with your health care professional before taking dietary supplements

There is no clear proof that specific foods, herbs, spices, or dietary supplements —such as vitamins or minerals—can help manage diabetes. Your health care professional may ask you to take vitamins or minerals if you can’t get enough from foods. Talk with your health care professional before you take any supplements, because some may cause side effects or affect how well your diabetes medicines work.

Research shows that regular physical activity helps people manage their diabetes and stay healthy. Benefits of physical activity may include

• lower blood glucose, blood pressure, and cholesterol levels
• better heart health
• healthier weight
• better mood and sleep
• better balance and memory

Talk with your health care professional before starting a new physical activity or changing how much physical activity you do. They may suggest types of activities based on your ability, schedule, meal plan, interests, and diabetes medicines. Your health care professional may also tell you the best times of day to be active or what to do if your blood glucose level goes out of the range recommended for you.

Do different types of physical activity

People with diabetes can be active, even if they take insulin or use technology such as insulin pumps .

Try to do different kinds of activities . While being more active may have more health benefits, any physical activity is better than none. Start slowly with activities you enjoy. You may be able to change your level of effort and try other activities over time. Having a friend or family member join you may help you stick to your routine.

The physical activities you do may need to be different if you are age 65 or older , are pregnant , or have a disability or health condition . Physical activities may also need to be different for children and teens . Ask your health care professional or health care team about activities that are safe for you.

Aerobic activities

Aerobic activities make you breathe harder and make your heart beat faster. You can try walking, dancing, wheelchair rolling, or swimming. Most adults should try to get at least 150 minutes of moderate-intensity physical activity each week. Aim to do 30 minutes a day on most days of the week. You don’t have to do all 30 minutes at one time. You can break up physical activity into small amounts during your day and still get the benefit. 1

Strength training or resistance training

Strength training or resistance training may make your muscles and bones stronger. You can try lifting weights or doing other exercises such as wall pushups or arm raises. Try to do this kind of training two times a week. 1

Balance and stretching activities

Balance and stretching activities may help you move better and have stronger muscles and bones. You may want to try standing on one leg or stretching your legs when sitting on the floor. Try to do these kinds of activities two or three times a week. 1

Some activities that need balance may be unsafe for people with nerve damage or vision problems caused by diabetes. Ask your health care professional or health care team about activities that are safe for you.

Stay safe during physical activity

Staying safe during physical activity is important. Here are some tips to keep in mind.

Drink liquids

Drinking liquids helps prevent dehydration , or the loss of too much water in your body. Drinking water is a way to stay hydrated. Sports drinks often have a lot of sugar and calories , and you don’t need them for most moderate physical activities.

Avoid low blood glucose

Check your blood glucose level before, during, and right after physical activity. Physical activity often lowers the level of glucose in your blood. Low blood glucose levels may last for hours or days after physical activity. You are most likely to have low blood glucose if you take insulin or some other diabetes medicines, such as sulfonylureas.

Ask your health care professional if you should take less insulin or eat carbs before, during, or after physical activity. Low blood glucose can be a serious medical emergency that must be treated right away. Take steps to protect yourself. You can learn how to treat low blood glucose , let other people know what to do if you need help, and use a medical alert bracelet.

Avoid high blood glucose and ketoacidosis

Taking less insulin before physical activity may help prevent low blood glucose, but it may also make you more likely to have high blood glucose. If your body does not have enough insulin, it can’t use glucose as a source of energy and will use fat instead. When your body uses fat for energy, your body makes chemicals called ketones .

High levels of ketones in your blood can lead to a condition called diabetic ketoacidosis (DKA) . DKA is a medical emergency that should be treated right away. DKA is most common in people with type 1 diabetes . Occasionally, DKA may affect people with type 2 diabetes  who have lost their ability to produce insulin. Ask your health care professional how much insulin you should take before physical activity, whether you need to test your urine for ketones, and what level of ketones is dangerous for you.

Take care of your feet

People with diabetes may have problems with their feet because high blood glucose levels can damage blood vessels and nerves. To help prevent foot problems, wear comfortable and supportive shoes and take care of your feet  before, during, and after physical activity.

If you have diabetes, managing your weight  may bring you several health benefits. Ask your health care professional or health care team if you are at a healthy weight  or if you should try to lose weight.

If you are an adult with overweight or obesity, work with your health care team to create a weight-loss plan. Losing 5% to 7% of your current weight may help you prevent or improve some health problems  and manage your blood glucose, cholesterol, and blood pressure levels. 2 If you are worried about your child’s weight  and they have diabetes, talk with their health care professional before your child starts a new weight-loss plan.

You may be able to reach and maintain a healthy weight by

• following a healthy meal plan
• consuming fewer calories
• being physically active
• getting 7 to 8 hours of sleep each night 3

If you have type 2 diabetes, your health care professional may recommend diabetes medicines that may help you lose weight.

Online tools such as the Body Weight Planner  may help you create eating and physical activity plans. You may want to talk with your health care professional about other options for managing your weight, including joining a weight-loss program  that can provide helpful information, support, and behavioral or lifestyle counseling. These options may have a cost, so make sure to check the details of the programs.

Your health care professional may recommend weight-loss surgery  if you aren’t able to reach a healthy weight with meal planning, physical activity, and taking diabetes medicines that help with weight loss.

If you are pregnant , trying to lose weight may not be healthy. However, you should ask your health care professional whether it makes sense to monitor or limit your weight gain during pregnancy.

Both diabetes and smoking —including using tobacco products and e-cigarettes—cause your blood vessels to narrow. Both diabetes and smoking increase your risk of having a heart attack or stroke , nerve damage , kidney disease , eye disease , or amputation . Secondhand smoke can also affect the health of your family or others who live with you.

If you smoke or use other tobacco products, stop. Ask for help . You don’t have to do it alone.

Feeling stressed, sad, or angry can be common for people with diabetes. Managing diabetes or learning to cope with new information about your health can be hard. People with chronic illnesses such as diabetes may develop anxiety or other mental health conditions .

Learn healthy ways to lower your stress , and ask for help from your health care team or a mental health professional. While it may be uncomfortable to talk about your feelings, finding a health care professional whom you trust and want to talk with may help you

• lower your feelings of stress, depression, or anxiety
• manage problems sleeping or remembering things
• see how diabetes affects your family, school, work, or financial situation

Ask your health care team for mental health resources for people with diabetes.

Sleeping too much or too little may raise your blood glucose levels. Your sleep habits may also affect your mental health and vice versa. People with diabetes and overweight or obesity can also have other health conditions that affect sleep, such as sleep apnea , which can raise your blood pressure and risk of heart disease.

NIDDK conducts and supports clinical trials in many diseases and conditions, including diabetes. The trials look to find new ways to prevent, detect, or treat disease and improve quality of life.

What are clinical trials for healthy living with diabetes?

Clinical trials—and other types of clinical studies —are part of medical research and involve people like you. When you volunteer to take part in a clinical study, you help health care professionals and researchers learn more about disease and improve health care for people in the future.

Researchers are studying many aspects of healthy living for people with diabetes, such as

• how changing when you eat may affect body weight and metabolism
• how less access to healthy foods may affect diabetes management, other health problems, and risk of dying
• whether low-carbohydrate meal plans can help lower blood glucose levels
• which diabetes medicines are more likely to help people lose weight

Find out if clinical trials are right for you .

Watch a video of NIDDK Director Dr. Griffin P. Rodgers explaining the importance of participating in clinical trials.

What clinical trials for healthy living with diabetes are looking for participants?

You can view a filtered list of clinical studies on healthy living with diabetes that are federally funded, open, and recruiting at www.ClinicalTrials.gov . You can expand or narrow the list to include clinical studies from industry, universities, and individuals; however, the National Institutes of Health does not review these studies and cannot ensure they are safe for you. Always talk with your primary health care professional before you participate in a clinical study.

This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.

NIDDK would like to thank: Elizabeth M. Venditti, Ph.D., University of Pittsburgh School of Medicine.

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Strength Training versus Stretching for Improving Range of Motion: A Systematic Review and Meta-Analysis

José afonso.

1 Centre for Research, Education, Innovation and Intervention in Sport (CIFI2D), Faculty of Sport of the University of Porto, Rua Dr. Plácido Costa, 91, 4200-450 Porto, Portugal; tp.pu.edaf@sevenj (J.A.); tp.pu.edaf@accazr (R.Z.); tp.pu.edaf@392009102pu (A.M.); tp.pu.edaf@534705102pu (A.A.M.)

Rodrigo Ramirez-Campillo

2 Department of Physical Activity Sciences, Universidad de Los Lagos, Lord Cochrane 1046, Osorno 5290000, Chile; [email protected]

3 Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, San Pio X, 2422, Providencia, Santiago 7500000, Chile

João Moscão

4 REP Exercise Institute, Rua Manuel Francisco 75-A 2 °C, 2645-558 Alcabideche, Portugal; moc.etutitsniper@otcatnoc

Tiago Rocha

5 Polytechnic of Leiria, Rua General Norton de Matos, Apartado 4133, 2411-901 Leiria, Portugal; [email protected]

Rodrigo Zacca

6 Porto Biomechanics Laboratory (LABIOMEP-UP), University of Porto, Rua Dr. Plácido Costa, 91, 4200-450 Porto, Portugal

7 Coordination for the Improvement of Higher Educational Personnel Foundation (CAPES), Ministry of Education of Brazil, Brasília 70040-020, Brazil

Alexandre Martins

André a. milheiro, joão ferreira.

8 Superior Institute of Engineering of Porto, Polytechnic Institute of Porto, Rua Dr. António Bernardino de Almeida, 431, 4249-015 Porto, Portugal; tp.ppi.pesi@8360021

Hugo Sarmento

9 Faculty of Sport Sciences and Physical Education, University of Coimbra, 3040-256 Coimbra, Portugal; [email protected]

Filipe Manuel Clemente

10 Escola Superior Desporto e Lazer, Instituto Politécnico de Viana do Castelo, Rua Escola Industrial e Comercial de Nun’Álvares, 4900-347 Viana do Castelo, Portugal

11 Instituto de Telecomunicações, Department of Covilhã, 1049-001 Lisboa, Portugal

Associated Data

Our data were made available with the submission.

(1) Background: Stretching is known to improve range of motion (ROM), and evidence has suggested that strength training (ST) is effective too. However, it is unclear whether its efficacy is comparable to stretching. The goal was to systematically review and meta-analyze randomized controlled trials (RCTs) assessing the effects of ST and stretching on ROM (INPLASY 10.37766/inplasy2020.9.0098). (2) Methods: Cochrane Library, EBSCO, PubMed, Scielo, Scopus, and Web of Science were consulted in October 2020 and updated in March 2021, followed by search within reference lists and expert suggestions (no constraints on language or year). Eligibility criteria: (P) Humans of any condition; (I) ST interventions; (C) stretching (O) ROM; (S) supervised RCTs. (3) Results: Eleven articles ( n = 452 participants) were included. Pooled data showed no differences between ST and stretching on ROM (ES = −0.22; 95% CI = −0.55 to 0.12; p = 0.206). Sub-group analyses based on risk of bias, active vs. passive ROM, and movement-per-joint analyses showed no between-protocol differences in ROM gains. (4) Conclusions: ST and stretching were not different in their effects on ROM, but the studies were highly heterogeneous in terms of design, protocols and populations, and so further research is warranted. However, the qualitative effects of all the studies were quite homogeneous.

1. Introduction

Joint range of motion (ROM) is the angle by which a joint moves from its resting position to the extremities of its motion in any given direction [ 1 ]. Improving ROM is a core goal for the general population [ 2 ], as well as in clinical contexts [ 3 ], such as in treating acute respiratory failure [ 4 ], plexiform neurofibromas [ 5 ], recovering from breast cancer-related surgery [ 6 ], and total hip replacement [ 7 ]. Several common clinical conditions negatively affect ROM, such as ankylosing spondylitis [ 8 ], cerebral palsy [ 9 ], Duchenne muscular dystrophy [ 10 ], osteoarthritis [ 11 ] rheumatoid arthritis [ 12 ]. Unsurprisingly, ROM gains are also relevant in different sports [ 13 ], such as basketball, baseball and rowing [ 14 , 15 , 16 ]. ROM is improved through increased stretch tolerance, augmented fascicle length and changes in pennation angle [ 17 ], as well as reduced tonic reflex activity [ 18 ]. Stretching is usually prescribed for increasing ROM in sports [ 19 , 20 ], clinical settings, such as chronic low back pain [ 21 ], rheumatoid arthritis [ 22 ], and exercise performance in general [ 23 ]. Stretching techniques, include static (active or passive), dynamic, or proprioceptive neuromuscular facilitation (PNF), all of which can improve ROM [ 2 , 24 , 25 , 26 , 27 ].

It should be noted that muscle weakness is associated with diminished ROM [ 28 , 29 , 30 ]. Strength training (ST) can be achieved through a number of methods, as long as resistance is applied to promote strength gains, and includes methods as diverse as using free weights or plyometrics [ 31 ]. Although ST primarily addresses muscle weakness, it has been shown to increase ROM [ 32 ]. For example, hip flexion and extension ROM of adolescent male hurdles was improved using plyometrics [ 33 ], while judo fighters improved ROM (shoulder flexion, extension, abduction and adduction; trunk flexion and extension; and hip flexion and extension) through resistance training [ 34 ]. The ROM gains, using resistance training, have also been described in relation to healthy elderly people for hip flexion and cervical extension [ 35 ], and isometric neck strength training, with an elastic band, in women with chronic nonspecific neck pain improved neck flexion, extension, rotation and lateral flexion [ 36 ]. ST that is focused on concentric and eccentric contractions has been shown to increase fascicle length [ 37 , 38 , 39 ]. Improvements in agonist-antagonist co-activation [ 40 ], reciprocal inhibition [ 41 ], and potentiated stretch-shortening cycles due to greater active muscle stiffness [ 42 ] may also explain why ST is a suitable method for improving ROM.

Nevertheless, studies comparing the effects of ST and stretching in ROM have presented conflicting evidence [ 43 , 44 ], and many have small sample sizes [ 45 , 46 ]. Developing a systematic review and meta-analysis may help summarize this conflicting evidence and increase statistical power, thus, providing clearer guidance for interventions [ 47 ]. Therefore, the aim of this systematic review and meta-analysis was to compare the effects of supervised and randomized ST versus stretching protocols on ROM in participants of any health and training status.

2. Materials and Methods

2.1. protocol and registration.

The methods and protocol registration were preregistered prior to conducting the review: INPLASY, no.202090098, DOI:10.37766/inplasy2020.9.0098.

2.2. Eligibility Criteria

Articles were eligible for inclusion if published in peer-reviewed journals, with no restrictions in language or publication date. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were adopted [ 48 ]. Participants, interventions, comparators, outcomes, and study design (P.I.C.O.S.) were established as follows: (i) Participants with no restriction regarding health, sex, age, or training status; (ii) ST interventions supervised by a certified professional. ST was defined as any method focused on developing strength, ranging from resistance training to plyometrics [ 31 ]; no limitations were placed with regard to intensity, volume, type of contractions and frequency, as it could excessively narrow the searches; (iii) comparators were supervised groups performing any form of stretching, including static stretching, passive stretching, dynamic stretching, and PNF [ 2 ], regardless of their intensity, duration or additional features; (iv) outcomes were ROM assessed in any joint, preferably through goniometry, but standardized tests such as the sit-and-reach were also acceptable; (v) randomized controlled trials (RCTs). RCTs reduce bias and better balance participant features between the groups [ 47 ], and are important for the advancement of sports science [ 49 ]. There were no limitations regarding intervention length.

The study excluded reviews, letters to editors, trial registrations, proposals for protocols, editorials, book chapters, and conference abstracts. Exclusion criteria, based on P.I.C.O.S., included: (i) Research with non-human animals; (ii) non-ST protocols or ST interventions combined with other methods (e.g., endurance); unsupervised interventions; (iii) stretching or ST + stretching interventions combined with other training methods (e.g., endurance); protocols without stretching; unsupervised interventions; (iv) studies not reporting ROM; (v) non-randomized interventions.

2.3. Information Sources and Search

Six databases were used to search and retrieve the articles in early October 2020: Cochrane Library, EBSCO, PubMed (including MEDLINE), Scielo, Scopus, and Web of Science (Core Collection). Boolean operators were applied to search the article title, abstract and/or keywords: (“strength training” OR “resistance training” OR “weight training” OR “plyometric*” OR “calisthenics”) AND (“flexibility” OR “stretching”) AND “range of motion” AND “random*”. The specificities of each search engine included: (i) Cochrane Library, items were limited to trials, including articles but excluding protocols, reviews, editorials and similar publications; (ii) EBSCO, the search was limited to articles in scientific, peer-reviewed journals (iii) PubMed, the search was limited to title or abstract; publications were limited to RCTs and clinical trials, excluding books and documents, meta-analyses, reviews and systematic reviews; (iv) in Scielo, Scopus and Web of Science, the publication type was limited to article; and (v) Web of Science, “topic” is the term used to refer to title, abstract and keywords.

An additional search was conducted within the reference lists of the included records. The list of articles and inclusion criteria were then sent to four experts to suggest additional references. The search strategy and consulted databases were not provided in this process to avoid biasing the experts’ searches. More detailed information is available as supplementary material .

Updated searches: on 8 March 2021, we conducted new searches in the databases. However, each database has specific approaches to filtering the searches by date. In Cochrane, we searched for articles entering the database in the previous 6 months. In EBSCO, we searched for all fields starting from October 2020 onwards. In PubMed, the entry date was set to 1 October 2020, onwards. In Scielo, Scopus and Web of Science, publication date was limited to 2020 and 2021.

2.4. Search Strategy

Here, we provide the specific example of search conducted in PubMed:

(((“strength training” [Title/Abstract] OR “resistance training” [Title/Abstract] OR “weight training” [Title/Abstract] OR “plyometric*” [Title/Abstract] OR “calisthenics” [Title/Abstract]) AND (“flexibility” [Title/Abstract] OR “stretching” [Title/Abstract])) AND (“range of motion” [Title/Abstract])) AND (“random*” [Title/Abstract]).

After this search, the filters RCT and Clinical Trial were applied.

2.5. Study Selection

J.A. and F.M.C. each conducted the initial search and selection stages independently, and then compared result to ensure accuracy. J.F. and T.R. independently reviewed the process to detect potential errors. When necessary, re-analysis was conducted until a consensus was achieved.

2.6. Data Collection Process

J.A., F.M.C., A.A.M. and J.F. extracted the data, while J.M., T.R., R.Z. and A.M. independently revised the process. Data for the meta-analysis were extracted by JA and independently verified by A.A.M. and R.R.C. Data were available for sharing.

2.7. Data Items

Data items: (i) Population: subjects, health status, sex/gender, age, training status, selection of subjects; (ii) intervention and comparators: Study length in weeks, weekly frequency of the sessions, weekly training volume in minutes, session duration in minutes, number of exercises per session, number of sets and repetitions per exercise, load (e.g., % 1 Repetition Maximum), full versus partial ROM, supervision ratio; in the comparators, modality of stretching applied was also considered; adherence rates were considered a posteriori ; (iii) ROM testing: joints and actions, body positions (e.g., standing, supine), mode of testing (i.e., active, passive, both), pre-testing warm-up, timing (e.g., pre- and post-intervention, intermediate assessments), results considered for a given test (e.g., average of three measures), data reliability, number of testers and instructions provided during testing; (iv) Outcomes: changes in ROM for intervention and comparator groups; (vi) funding and conflicts of interest.

2.8. Risk of Bias in Individual Studies

The risk of bias (RoB) in individual studies was assessed using the Cochrane risk-of-bias tool for randomized trials (RoB 2) [ 50 ]. J.A. and A.M. independently completed RoB analysis, which was reviewed by F.M.C. Where inconsistencies emerged, the original articles were re-analyzed until a consensus was achieved.

2.9. Summary Measures

Meta-analysis was conducted when ≥3 studies were available [ 51 ]. Pre- and post-intervention means and standard deviations (SDs) for dependent variables were used after being converted to Hedges’s g effect size (ES) [ 51 ]. When means and SDs were not available, they were calculated from 95% confidence intervals (CIs) or standard error of mean (SEM), using Cochrane’s RevMan Calculator for Microsoft Excel [ 52 ]. When ROM data from different groups (e.g., men and women) or different joints (e.g., knee and ankle) was pooled, weighted formulas were applied [ 47 ].

2.10. Synthesis of Results

The inverse variance random-effects model for meta-analyses [ 53 , 54 ] was used to allocate a proportionate weight to trials based on the size of their individual standard errors [ 55 ], and accounting for heterogeneity across studies [ 56 ]. The ESs were presented alongside 95% CIs and interpreted using the following thresholds [ 57 ]: <0.2, trivial; 0.2–0.6, small; >0.6–1.2, moderate; >1.2–2.0, large; >2.0–4.0, very large; >4.0, extremely large. Heterogeneity was assessed using the I 2 statistic, with values of <25%, 25–75%, and >75% considered to represent low, moderate, and high levels of heterogeneity, respectively [ 58 ]. Data used for meta-analysis is available in a supplementary Excel file .

2.11. Risk of Bias Across Studies

Publication bias was explored using the extended Egger’s test [ 59 ], with p < 0.05 implying bias. To adjust for publication bias, a sensitivity analysis was conducted using the trim and fill method [ 60 ], with L0 as the default estimator for the number of missing studies [ 61 ].

2.12. Moderator Analyses

Using a random-effects model and independent computed single factor analysis, potential sources of heterogeneity likely to influence the effects of training interventions were selected, including (i) ROM type (i.e., passive versus active), (ii) studies RoB in randomization, and (iii) studies RoB in measurement of the outcome [ 62 ]. These analyses were decided post-protocol registration.

All analyses were carried out using the Comprehensive Meta-Analysis program (version 2; Biostat, Englewood, NJ, USA). Statistical significance was set at p ≤ 0.05. Data for the meta-analysis were extracted by JA and independently verified by A.A.M. and R.R.C.

2.13. Quality and Confidence in Findings

Although not planned in the registered protocol, we decided to abide by the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) [ 63 ], which addresses five dimensions that can downgrade studies when assessing the quality of evidence in RCTs. RoB, inconsistency (through heterogeneity measures), and publication bias were addressed above and were considered a priori . Directness was guaranteed by design, as no surrogates were used for any of the pre-defined P.I.C.O. dimensions. Imprecision was assessed on the basis of 95% CIs.

3.1. Study Selection

An initial search returned 194 results (52 in Cochrane Library, 11 in EBSCO, 11 in PubMed, 9 in Scielo, 88 in Scopus, and 23 in Web of Science). After removal of duplicates, 121 records remained. Screening the titles and abstracts for eligibility criteria resulted in the exclusion of 106 articles: 26 were not original research articles (e.g., trial registrations, reviews), 24 were out of scope, 48 did not have the required intervention or comparators, five did not assess ROM, two were non-randomized and one was unsupervised. Fifteen articles were eligible for full-text analysis. One article did not have the required intervention [ 64 ], and two did not have the needed comparators [ 65 , 66 ]. In one article, the ST and stretching groups performed a 20–30 min warm-up following an unspecified protocol [ 67 ]. In another, the intervention and comparator were unsupervised [ 68 ], and in one the stretching group was unsupervised [ 69 ]. Finally, in one article, 75% of the training sessions were unsupervised [ 70 ]. Therefore, eight articles were included at this stage [ 33 , 43 , 44 , 45 , 46 , 71 , 72 , 73 ].

A manual search within the reference lists of the included articles revealed five additional potentially fitting articles. Two lacked the intervention group required [ 74 , 75 ], and two were non-randomized [ 76 , 77 ]. One article met the inclusion criteria [ 78 ]. Four experts revised the inclusion criteria and the list of articles and suggested eight articles based on their titles and abstracts. Six were excluded: interventions were multicomponent [ 79 , 80 ]; comparators performed no exercise [ 81 , 82 ]; out of scope [ 83 ]; and unsupervised stretching group [ 84 ]. Two articles were included [ 85 , 86 ], increasing the list to eleven articles [ 33 , 43 , 44 , 45 , 46 , 71 , 72 , 73 , 78 , 85 , 86 ], with 452 participants eligible for meta-analysis ( Figure 1 ). Updated searches: in the renewed searches, 28 records emerged, of which two passed the screening. However, these two records had already been included in our final sample. Therefore, no new article was included.

Flowchart describing the study selection process.

3.2. Study Characteristics and Results

The data items can be found in Table 1 . The study of Wyon, Smith and Koutedakis [ 73 ] required consultation of a previous paper [ 87 ] to provide essential information. Samples ranged from 27 [ 46 ] to 124 subjects [ 43 ], including: Trained participants, i.e., engaging in systematic exercise programs [ 33 , 45 , 72 , 73 ], healthy sedentary participants [ 44 , 71 , 78 ], sedentary and trained participants [ 86 ], workers with chronic neck pain [ 46 ], participants with fibromyalgia [ 85 ], and elderly participants with difficulties in at least one of four tasks: transferring, bathing, toileting, and walking [ 43 ]. Seven articles included only women [ 45 , 73 , 78 , 85 ] or predominantly women [ 43 , 44 , 46 ]; three investigated only men [ 33 , 86 ] or predominantly men [ 71 ]; and one article had a balanced mixture of men and women [ 72 ].

Characteristics of included randomized trials.

Legend: N/A—Information not available. ST—Strength training. STRE—Stretching. ROM—Range of motion. MVC—Maximum voluntary contraction. PNF—Proprioceptive neuromuscular facilitation. * Non-exercise groups are not considered in this column.

Interventions lasted between five [ 71 ] and 16 weeks [ 78 ]. Minimum weekly training frequency was two sessions [ 46 , 85 ] and maximum was five [ 73 ]. Six articles provided insufficient information concerning session duration [ 44 , 45 , 72 , 73 , 78 , 86 ]. Ten articles vaguely defined training load for the ST and stretching groups [ 33 , 43 , 46 , 71 , 72 , 85 , 86 ], or for stretching groups [ 44 , 45 , 78 ]. Six articles did not report on using partial or full ROM during ST exercises [ 33 , 43 , 45 , 46 , 72 , 78 ]. Different stretching modalities were implemented: static active [ 44 , 46 , 71 , 78 , 85 , 86 ], dynamic [ 43 , 45 ], dynamic with a 10-s hold [ 33 ], static active in one group and static passive in another [ 73 ], and a combination of dynamic, static active, and PNF [ 72 ].

Hip joint ROM was assessed in seven articles [ 33 , 43 , 45 , 71 , 72 , 73 , 78 ], knee ROM in five [ 43 , 44 , 45 , 71 , 86 ], shoulder ROM in four [ 43 , 45 , 71 , 85 ], elbow and trunk ROM in two [ 43 , 45 ], and cervical spine [ 46 ] and the ankle joint ROM in one article [ 43 ]. In one article, active ROM (AROM) was tested for the trunk, while passive ROM (PROM) was tested for the other joints [ 43 ]. In one article, PROM was tested for goniometric assessments and AROM for hip flexion [ 45 ]. In another, AROM was assessed for the shoulder and PROM for the hip and knee [ 71 ]. Three articles only assessed PROM [ 44 , 72 , 86 ], and four AROM [ 33 , 46 , 78 , 85 ], while one assessed both for the same joint [ 73 ].

In seven articles [ 33 , 46 , 71 , 72 , 78 , 85 ], ST and stretching groups significantly improved ROM, and the differences between the groups were non-significant. In one article, the ST group had significant improvements in 8 of 10 ROM measures, while dynamic stretching did not lead to improvement in any of the groups [ 43 ]. In another article, the three groups significantly improved PROM, without between-group differences; the ST and the static active stretching groups also significantly improved AROM [ 73 ]. In two articles, none of the groups improved ROM [ 44 , 45 ].

3.3. Risk of Bias in Individual Studies

Table 2 presents assessments of RoB. Bias arising from the randomization process was low in four articles [ 43 , 45 , 73 , 85 ], moderate in one [ 46 ] and high in six [ 33 , 44 , 71 , 72 , 78 , 86 ]. Bias due to deviations from intended interventions, missing outcome data, and selection of the reported results was low. Bias in measurement of the outcome was low in six articles [ 44 , 45 , 46 , 78 , 85 , 86 ], but high in five [ 33 , 43 , 71 , 72 , 73 ].

Assessments of risk of bias (Cochrane’s RoB 2).

3.4. Synthesis of Results

Comparisons were performed between ST and stretching groups, involving eleven articles and 452 participants. Global effects on ROM were achieved pooling data from the different joints. One article did not have the data required [ 44 ], but the authors supplied it upon request. For another article [ 45 ], we also requested data relative to the goniometric evaluations, but obtained no response. Therefore, only data from the sit-and-reach test were used. For one article [ 46 ], means and SDs were obtained from 95% CIs, while in another [ 85 ], SDs were extracted from SEMs using Cochrane’s RevMan Calculator.

From the five articles, including both genders, four provided pooled data, with no distinction between genders [ 43 , 44 , 46 , 71 ]. One article presented data separated by gender, without significant differences between men and women in response to interventions [ 72 ]. Weighted formulas were applied sequentially for combining means and SDs of groups within the same study [ 47 ]. Two studies presented the results separated by left and right lower limbs, with both showing similar responses to the interventions [ 33 , 73 ]; outcomes were combined using the same weighted formulas for the means and SDs. Five articles only presented one decimal place [ 33 , 43 , 46 , 72 , 78 ], and so all values were rounded for uniformity.

Effects of ST versus stretching on ROM: no significant difference was noted between ST and stretching (ES = −0.22; 95% CI = −0.55 to 0.12; p = 0.206; I 2 = 65.4%; Egger’s test p = 0.563; Figure 2 ). The relative weight of each study in the analysis ranged from 6.4% to 12.7% (the size of the plotted squares in Figure 2 reflects the statistical weight of each study).

Forest plot of changes in ROM after participating in stretching-based compared to Scheme 95. confidence intervals (CI). The size of the plotted squares reflects the statistical weight of the study.

3.5. Additional Analyses

Effects of ST versus stretching on ROM, moderated by study RoB in randomization : No significant sub-group differences in ROM changes ( p = 0.256) was found when programs with high RoB (6 studies; ES = −0.41; 95% CI = −1.02 to 0.20; within-group I 2 = 77.5%) were compared to programs with low RoB (4 studies; ES = −0.03; 95% CI = −0.29 to 0.23; within-group I 2 = 0.0%) ( Figure 3 ).

Forest plot of changes in ROM after participating in stretching-based compared to Scheme 95. confidence intervals (CI).

Effects of ST versus stretching on ROM, moderated by study RoB in measurement of the outcome : No significant sub-group difference in ROM changes ( p = 0.320) was found when programs with high RoB (5 studies; ES = −0.04; 95% CI = −0.31 to 0.24; within-group I 2 = 8.0%) were compared to programs with low RoB (6 studies; ES = −0.37; 95% CI = −0.95 to 0.22; within-group I 2 = 77.3%) ( Figure 4 ).

Effects of ST versus stretching on ROM, moderated by ROM type (active vs. passive) : No significant sub-group difference in ROM changes ( p = 0.642) was found after training programs that assessed active (8 groups; ES = −0.15; 95% CI = −0.65 to 0.36; within-group I 2 = 78.7%) compared to passive ROM (6 groups; ES = −0.01; 95% CI = −0.27 to 0.24; within-group I 2 = 15.3%) ( Figure 5 ).

Effects of ST versus stretching on hip flexion ROM: Seven studies provided data for hip flexion ROM (pooled n = 294). There was no significant difference between ST and stretching interventions (ES = −0.24; 95% CI = −0.82 to 0.34; p = 0.414; I 2 = 80.5%; Egger’s test p = 0.626; Figure 6 ). The relative weight of each study in the analysis ranged from 12.0% to 17.4% (the size of the plotted squares in Figure 6 reflects the statistical weight of each study).

Forest plot of changes in hip flexion ROM after participating in stretching-based compared to strength-based training interventions. Values shown are effect sizes (Hedges’s g) with 95% confidence intervals (CI). The size of the plotted squares reflects the statistical weight of the study.

Effects of ST versus stretching on hip flexion ROM, moderated by study RoB in randomization: No significant sub-group difference in hip flexion ROM changes ( p = 0.311) was found when programs with high RoB in randomization (4 studies; ES = −0.46; 95% CI = −1.51 to 0.58; within-group I 2 = 86.9%) were compared to programs with low RoB in randomization (3 studies; ES = 0.10; 95% CI = −0.20 to 0.40; within-group I 2 = 0.0%) ( Figure 7 ).

Forest plot of changes in hip flexion ROM after participating in stretching-based compared to strength-based training interventions with high versus low RoB in randomization. Values shown are effect sizes (Hedges’s g) with 95% confidence intervals (CI).

Effects of ST versus stretching on hip flexion ROM, moderated by ROM type (active vs. passive): No significant sub-group difference in hip flexion ROM changes ( p = 0.466) was found after the programs assessed active (4 groups; ES = −0.38; 95% CI = −1.53 to 0.76; within-group I 2 = 87.1%) compared to passive ROM (4 groups; ES = 0.08; 95% CI = −0.37 to 0.52; within-group I 2 = 56.5%) ( Figure 8 ).

Forest plot of changes in hip flexion ROM after participating in stretching-based compared to strength-based training interventions assessing active or passive ROM. Values shown are effect sizes (Hedges’s g) with 95% confidence intervals (CI).

Effects of ST versus stretching on knee extension ROM: Four studies provided data for knee extension ROM (pooled n = 223). There was no significant difference between ST and stretching interventions (ES = 0.25; 95% CI = −0.02 to 0.51; p = 0.066; I 2 = 0.0%; Egger’s test p = 0.021; Figure 9 ). After the application of the trim and fill method, the adjusted values changed to ES = 0.33 (95% CI = 0.10 to 0.57), favoring ST. The relative weight of each study in the analysis ranged from 11.3% to 54.2% (the size of the plotted squares in Figure 9 reflects the statistical weight of each study).

Forest plot of changes in knee extension ROM after participating in stretching-based compared to strength-based training interventions (all assessed passive ROM). Values shown are effect sizes (Hedges’s g) with 95% confidence intervals (CI). The size of the plotted squares reflects the statistical weight of the study.

One article behaved as an outlier in all comparisons, favoring stretching [ 78 ], but after sensitivity analysis the results remained unchanged ( p > 0.05), with all ST versus stretching comparisons remaining non-significant.

3.6. Confidence in Cumulative Evidence

Table 3 presents GRADE assessments. ROM is a continuous variable, and so a high degree of heterogeneity was expected [ 88 ]. Imprecision was moderate, likely reflecting the fact that ROM is a continuous variable. Overall, both ST and stretching consistently promoted ROM gains, but no recommendation could be made favoring one protocol.

GRADE assessments for the certainty of evidence.

1—Meta-analyses moderated by RoB showed no differences between studies with low and high risk. 2—Because ROM is a continuous variable, high heterogeneity was expected. However, this heterogeneity is mostly between small and large beneficial effects. No adverse effects were reported. 3—Expected because ROM is a continuous variable. Furthermore, imprecision referred to small to large beneficial effects. 4—Both strength training and stretching presented benefits without reported adverse effects.

4. Discussion

4.1. summary of evidence.

The aim of this systematic review and meta-analysis was to compare the effects of supervised and randomized ST compared to stretching protocols on ROM, in participants of any health and training status. Qualitative synthesis showed that ST and stretching interventions were not statistically different in improving ROM. However, the studies were highly heterogeneous with regard to the nature of the interventions and moderator variables, such as gender, health, or training status. This had been reported in the original manuscripts as well. A meta-analysis, including 11 articles and 452 participants, showed that ST and stretching interventions were not statistically different in active and passive ROM changes, regardless of RoB in the randomization process, or in measurement of the outcome. RoB was low for deviations from intended interventions, missing outcome data, and selection of the reported results. No publication bias was detected.

High heterogeneity is expected in continuous variables [ 88 ], such as ROM. However, more research should be conducted to afford sub-group analysis according to characteristics of the analyzed population, as well as protocol features. For example, insufficient reporting of training volume and intensity meant it was impossible to establish effective dose-response relationships, although a minimum of five weeks of intervention [ 71 ], and two weekly sessions were sufficient to improve ROM [ 46 , 85 ]. Studies were not always clear with regard to the intensity used in ST and stretching protocols. Assessment of stretching intensity is complex, but a practical solution may be to apply scales of perceived exertion [ 73 ], or the Stretching Intensity Scale [ 89 ]. ST intensity may also moderate effects on ROM [ 90 ], and ST with full versus partial ROM may have distinct neuromuscular effects [ 81 ] and changes in fascicle length [ 37 ]. Again, the information was insufficient to discuss these factors, which could potentially explain part of the heterogeneity of results. This precludes advancing stronger conclusions and requires further research to be implemented.

Most studies showed ROM gains in ST and stretching interventions, but in two studies, neither group showed improvements [ 44 , 45 ]. Although adherence rates were unreported by Aquino, Fonseca, Goncalves, Silva, Ocarino and Mancini [ 44 ], they were above 91.7% in Leite, De Souza Teixeira, Saavedra, Leite, Rhea and Simão [ 45 ], thus providing an unlikely explanation for these results. In the study by Aquino, Fonseca, Goncalves, Silva, Ocarino and Mancini [ 44 ], the participants increased their stretch tolerance, and the ST group changed the peak torque angle, despite no ROM gains. The authors acknowledged that there was high variability in measurement conditions (e.g., room temperature), which could have interfered with calculations. Leite, De Souza Teixeira, Saavedra, Leite, Rhea and Simão [ 45 ] suggested that the use of dynamic instead of static stretching could explain the lack of ROM gains in the stretching and stretching + ST groups. However, other studies using dynamic stretching have shown ROM gains [ 33 , 43 ]. Furthermore, Leite, De Souza Teixeira, Saavedra, Leite, Rhea and Simão [ 45 ] provided no interpretation for the lack of ROM gains in the ST group.

Globally, however, both ST and stretching were effective in improving ROM. We asked what the reason for ST to improve ROM in a manner that is not statistically distinguishable from stretching? A first thought might be to speculate that perhaps the original studies used sub-threshold stretching intensities and/or durations. However, the hypothesis that ST has intrinsic merit for improving ROM should also be considered. ST with an eccentric focus demands the muscles to produce force on elongated positions, and a meta-analysis showed limited-to-moderate evidence that eccentric ST is associated with increases in fascicle length [ 91 ]. Likewise, a recent study showed that 12 sessions of eccentric ST increased fascicle length of the biceps femoris long head [ 38 ]. However, ST with an emphasis in concentric training has been shown to increase fascicle length when full ROM was required [ 37 ]. In a study with nine older adults, ST increased fascicle length in both the eccentric and concentric groups, albeit more prominently in the former [ 92 ]. Conversely, changes in pennation angle were superior in the concentric group (35% increase versus 5% increase). Plyometric training can also increase plantar flexor tendon extensibility [ 42 ].

One article showed significant reductions in pain associated with increases in strength [ 46 ]. Therefore, decreased pain sensitivity may be another mechanism by which ST promotes ROM gains. An improved agonist-antagonist coactivation is another possible mechanism promoting ROM gains, through better adjusted force ratios [ 40 , 73 ]. Also, some articles included in the meta-analysis assessed other outcomes in addition to ROM, and these indicated that ST programs may have additional advantages when compared to stretching, such as greater improvements in neck flexors endurance [ 46 ], ten repetition maximum Bench Press and Leg Press [ 45 , 78 ], and countermovement jump and 60-m sprint with hurdles [ 33 ] which may favor the choice of ST over stretching interventions.

4.2. Limitations

After protocol registration, we chose to improve upon the design, namely adding two dimensions (directness and imprecision) that would provide a complete GRADE assessment. Furthermore, subgroup analyses were not planned a priori . There is a risk of multiple subgroup analyses generating a false statistical difference, merely to the number of analyses conducted [ 47 ]. However, all analyses showed an absence of significant differences and therefore provide a more complete understanding that the effects of ST or stretching on ROM are consistent across conditions. Looking backwards, perhaps removing the filters used in the initial searches could have provided a greater number of records. Notwithstanding, it would also likely provide a huge number of non-relevant records, including opinion papers and reviews. Moreover, consultation with four independent experts may hopefully have resolved this shortcoming.

Due to the heterogeneity of populations analysed, sub-group analysis according to sex or age group were not possible, and so it would be important to explore if these features interact with the protocols in meaningful ways. Moreover, there was a predominance of studies with women, meaning more research with men is advised. There was also a predominance of assessments of hip joint ROM, followed by knee and shoulder, with the remaining joints receiving little to no attention. In addition, dose-response relationships could not be addressed, mainly due to poor reporting. However, the qualitative findings of all the studies were very homogeneous, with statistical significance tests failing to show differences between ST and stretching protocols.

5. Conclusions

Overall, ST and stretching were not statistically different in ROM improvements, both in short-term interventions [ 71 ], and in longer-term protocols [ 78 ], suggesting that a combination of neural and mechanical factors is at play. However, the heterogeneity of study designs and populations precludes any definite conclusions and invites researchers to delve deeper into this phenomenon. Notwithstanding this observation, the qualitative effects were quite similar across studies. Therefore, if ROM gains are a desirable outcome, both ST and stretching reveal promising effects, but future research should better explore this avenue. In addition, the studies included in this review showed that ST had a few advantages in relation to stretching, as was explored in the discussion. Furthermore, session duration may negatively impact adherence to an exercise program [ 93 ]. If future research confirms that ST generates ROM gains similar to those obtained with stretching, clinicians may prescribe smaller, more time-effective programs when deemed convenient and appropriate, thus eventually increasing patient adherence rates. Alternatively, perhaps studies using stretching exercises should better assess their intensity and try to establish minimum thresholds for their efficacy in improving ROM.

Acknowledgments

Richard Inman: language editing and proof reading. Pedro Morouço: pre-submission scientific review of the manuscript. Daniel Moreira-Gonçalves and Fábio Nakamura, plus two experts that chose to remain anonymous: Review of inclusion criteria and included articles, and proposal of additional articles to be included in the systematic review and meta-analysis. Filipe Manuel Clemente: This work is supported by Fundação para a Ciência e Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior through national funds and when applicable co-funded EU funds under the project UIDB/50008/2020.

Supplementary Materials

The following are available online at https://www.mdpi.com/article/10.3390/healthcare9040427/s1 .

Author Contributions

We followed ICJME guidelines. Therefore, all authors have provided substantial contributions for the conceptualization and design of the study, acquisition, analysis and interpretation of data, as well as drafting and revising the manuscript critically. J.A., R.R.-C. and F.M.C. conceptualized the work and were actively involved in all stages of the manuscript. A.M., A.A.M., J.F., J.M., T.R. and R.Z. were more deeply involved in the methods and results. H.S. was more deeply invested in the rationale and discussion. All authors have read and agreed to the published version of the manuscript. Furthermore, all authors agree to be accountable for all aspects of the work. Contributors that did not meet these parameters are not listed as authors but are named in the acknowledgements.

No funding to declare.

Institutional Review Board Statement

Not applicable, since it was a review.

Informed Consent Statement

Data availability statement, conflicts of interest.

J.M. owns a company focused on Personal Trainer’s education but made no attempt to bias the team in protocol design and search process, and had no role in study selection or in extracting data for meta-analyses. The multiple cross-checks described in the methods provided objectivity to data extraction and analysis. Additionally, J.M. had no financial involvement in this manuscript. The other authors have no conflict of interest to declare.

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