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

Abstract Background A growing body of literature is available regarding the effects of plyometric jump training (PJT) on measures of physical fitness (PF) and sport-specific performance (SSP) in-water sports athletes (WSA, i.e. those competing in sports that are practiced on [e.g. rowing] or in [e.g. swimming; water polo] water). Indeed, incoherent findings have been observed across individual studies making it difficult to provide the scientific community and coaches with consistent evidence. As such, a comprehensive systematic literature search should be conducted to clarify the existent evidence, identify the major gaps in the literature, and offer recommendations for future studies. Aim To examine the effects of PJT compared with active/specific-active controls on the PF (one-repetition maximum back squat strength, squat jump height, countermovement jump height, horizontal jump distance, body mass, fat mass, thigh girth) and SSP (in-water vertical jump, in-water agility, time trial) outcomes in WSA, through a systematic review with meta-analysis of randomized and non-randomized controlled studies. Methods The electronic databases PubMed, Scopus, and Web of Science were searched up to January 2022. According to the PICOS approach, the eligibility criteria were: (population) healthy WSA; (intervention) PJT interventions involving unilateral and/or bilateral jumps, and a minimal duration of ≥ 3 weeks; (comparator) active (i.e. standard sports training) or specific-active (i.e. alternative training intervention) control group(s); (outcome) at least one measure of PF (e.g. jump height) and/or SSP (e.g. time trial) before and after training; and (study design) multi-groups randomized and non-randomized controlled trials. The Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the included studies. The DerSimonian and Laird random-effects model was used to compute the meta-analyses, reporting effect sizes (ES, i.e. Hedges’ g ) with 95% confidence intervals (95% CIs). Statistical significance was set at p ≤ 0.05. Certainty or confidence in the body of evidence for each outcome was assessed using Grading of Recommendations Assessment, Development, and Evaluation (GRADE), considering its five dimensions: risk of bias in studies, indirectness, inconsistency, imprecision, and risk of publication bias. Results A total of 11,028 studies were identified with 26 considered eligible for inclusion. The median PEDro score across the included studies was 5.5 (moderate-to-high methodological quality). The included studies involved a total of 618 WSA of both sexes (330 participants in the intervention groups [31 groups] and 288 participants in the control groups [26 groups]), aged between 10 and 26 years, and from different sports disciplines such as swimming, triathlon, rowing, artistic swimming, and water polo. The duration of the training programmes in the intervention and control groups ranged from 4 to 36 weeks. The results of the meta-analysis indicated no effects of PJT compared to control conditions (including specific-active controls) for in-water vertical jump or agility (ES = − 0.15 to 0.03; p = 0.477 to 0.899), or for body mass, fat mass, and thigh girth (ES = 0.06 to 0.15; p = 0.452 to 0.841). In terms of measures of PF, moderate-to-large effects were noted in favour of the PJT groups compared to the control groups (including specific-active control groups) for one-repetition maximum back squat strength, horizontal jump distance, squat jump height, and countermovement jump height (ES = 0.67 to 1.47; p = 0.041 to &lt; 0.001), in addition to a small effect noted in favour of the PJT for SSP time-trial speed (ES = 0.42; p = 0.005). Certainty of evidence across the included studies varied from very low-to-moderate. Conclusions PJT is more effective to improve measures of PF and SSP in WSA compared to control conditions involving traditional sport-specific training as well as alternative training interventions (e.g. resistance training). It is worth noting that the present findings are derived from 26 studies of moderate-to-high methodological quality, low-to-moderate impact of heterogeneity, and very low-to-moderate certainty of evidence based on GRADE. Trial registration The protocol for this systematic review with meta-analysis was published in the Open Science platform (OSF) on January 23, 2022, under the registration doi https://doi.org/10.17605/OSF.IO/NWHS3 (internet archive link: https://archive.org/details/osf-registrations-nwhs3-v1 ). 

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Effects of Plyometric Jump Training on Measures of Physical Fitness and Sport-Specific Performance of Water Sports Athletes: A Systematic Review with Meta-analysis

The Ballistic Exercise of the Lower Limb (BELL) trial examined efficacy and safety of a pragmatic hardstyle kettlebell training program in older adults. Insufficiently active men and women aged 59-79 years, were recruited to a 6-month repeated measures study, involving 3-months usual activity and 3-months progressive hardstyle kettlebell training. Health-related physical fitness outcomes included: grip strength [GS], 6-min walk distance [6MWD], resting heart rate [HR], stair-climb [SC], leg extensor strength [LES], hip extensor strength [HES], Sit-To-Stand [STS], vertical jump [CMVJ], five-times floor transfer [5xFT], 1RM deadlift, body composition (DXA), attendance, and adverse events. Sixteen males (68.8 {+/-} 4.6 yrs, 176.2 {+/-} 7.8 cm, 90.7 {+/-} 11.0 kg, 29.2 {+/-} 2.6 kg/m2) and sixteen females (68.6 {+/-} 4.7 yrs, 163.9 {+/-} 5.4 cm, 70.4 {+/-} 12.7 kg, 26.3 {+/-} 4.9 kg/m2) were recruited. Compliance to the supervised exercise program was very high (91.5%). Kettlebell training increased GS (R: MD = 7.1 kg 95% CI [4.9, 9.3], p < 0.001, L: MD = 6.3 kg 95% CI [4.1, 8.4], p < 0.001), 6MWD (41.7 m, 95% CI [17.9, 65.5], p < .001), 1RM (16.2 kg, 95% CI [2.4, 30.0], p = 0.013), 30s STS (3.3 reps, 95% CI [0.9, 5.7], p = 0.003), LES (R: MD = 61.6 N, 95% CI [4.4, 118.8], p = 0.028), HES (L: MD = 21.0 N, 95% CI [4.2, 37.8], p = 0.007), appendicular skeletal lean mass (MD = 0.65 kg, 95% CI [0.08, 1.22], p = 0.016), self-reported health change (17.1%, 95% CI [4.4, 29.8], p = 0.002) and decreased SC time (2.7 sec, 95% CI [0.2, 5.2], p = 0.025), 5xFT time (6.0 sec, 95% CI [2.2, 9.8], p < 0.001) and resting HR (7.4 bpm, 95% CI [0.7, 14.1], p = 0.032). There were four non-serious adverse events. Mean individual training load for group training sessions during the trial was 100,977 {+/-} 9,050 kg. High-intensity hardstyle kettlebell training was well tolerated and improved grip strength and measures of health-related physical fitness in insufficiently active older adults.

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Effects of supervised high-intensity hardstyle kettlebell training on grip strength and health-related physical fitness in insufficiently active older adults: The BELL pragmatic controlled trial

Abstract Background Although it is known that resistance training can be as effective as stretch training to increase joint range of motion, to date no comprehensive meta-analysis has investigated the effects of resistance training on range of motion with all its potential affecting variables. Objective The objective of this systematic review with meta-analysis was to evaluate the effect of chronic resistance training on range of motion compared either to a control condition or stretch training or to a combination of resistance training and stretch training to stretch training, while assessing moderating variables. Design For the main analysis, a random-effect meta-analysis was used and for the subgroup analysis a mixed-effect model was implemented. Whilst subgroup analyses included sex and participants’ activity levels, meta-regression included age, frequency, and duration of resistance training. Data Sources Following the systematic search in four databases (PubMed, Scopus, SPORTDiscus, and Web of Science) and reference lists, 55 studies were found to be eligible. Eligibility Criteria Controlled or randomized controlled trials that separately compared the training effects of resistance training exercises with either a control group, stretching group, or combined stretch and resistance training group on range of motion in healthy participants. Results Resistance training increased range of motion (effect size [ES] = 0.73; p &lt; 0.001) with the exception of no significant range of motion improvement with resistance training using only body mass. There were no significant differences between resistance training versus stretch training (ES = 0.08; p = 0.79) or between resistance training and stretch training versus stretch training alone (ES = − 0.001; p = 0.99). Although “trained or active people” increased range of motion (ES = 0.43; p &lt; 0.001) “untrained and sedentary” individuals had significantly ( p = 0.005) higher magnitude range of motion changes (ES = 1.042; p &lt; 0.001). There were no detected differences between sex and contraction type. Meta-regression showed no effect of age, training duration, or frequency. Conclusions As resistance training with external loads can improve range of motion, stretching prior to or after resistance training may not be necessary to enhance flexibility. 

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Resistance Training Induces Improvements in Range of Motion: A Systematic Review and Meta-Analysis

Abstract Background The current literature on the chronic effects of static stretching (SS) exercises on muscle strength and power is unclear and controversial. Objective We aimed to examine the chronic effects of SS exercises on muscle strength and power as well as flexibility in healthy individuals across the lifespan. Design Systematic review with meta-analysis of (randomized) controlled trials. Data Sources A systematic literature search was conducted in the databases PubMed, Web of Science, Cochrane Library, and SPORTDiscus up to May 2022. Eligibility Criteria for Selecting Studies We included studies that investigated the chronic effects of SS exercises on at least one muscle strength and power outcome compared to an active/passive control group or the contralateral leg (i.e., using between- or within-study designs, respectively) in healthy individuals, irrespective of age, sex, and training status. Results The main findings of 41 studies indicated trivial-to-small positive effects of chronic SS exercises on muscle strength (standardized mean difference [SMD] = 0.21, [95% confidence interval 0.10–0.32], p = 0.001) and power (SMD = 0.19, 95% confidence interval 0.12–0.26], p &lt; 0.001). For flexibility, moderate-to-large increases were observed (SMD = 0.96, [95% confidence interval 0.70–1.22], p &lt; 0.001). Subgroup analyses, taking the participants’ training status into account, revealed a larger muscle strength improvement for sedentary (SMD = 0.58, p &lt; 0.001) compared with recreationally active participants (SMD = 0.16, p = 0.029). Additionally, larger flexibility gains were observed following passive (SMD = 0.97, p &lt; 0.001) compared with active SS exercises (SMD = 0.59, p = 0.001). The chronic effects of SS on muscle strength were moderated by the proportion of female individuals in the sample ( β = 0.004, p = 0.042), with higher proportions experiencing larger gains. Other moderating variables included mean age ( β = 0.011, p &lt; 0.001), with older individuals showing larger muscle strength gains, and the number of repetitions per stretching exercise and session ( β = 0.023, p = 0.004 and β = 0.013, p = 0.008, respectively), with more repetitions associated with larger muscle strength improvements. Muscle power was also moderated by mean age ( β = 0.006, p = 0.007) with larger gains in older individuals. The meta-regression analysis indicated larger flexibility gains with more repetitions per session ( β = 0.094, p = 0.016), more time under stretching per session ( β = 0.090, p = 0.026), and more total time under stretching ( β = 0.078, p = 0.034). Conclusions The main findings indicated that chronic SS exercises have the potential to improve muscle strength and power. Such improvements appear to benefit sedentary more than recreationally active participants. Likewise, chronic SS exercises result in a marked enhancement in flexibility with larger effects of passive, as compared with active, SS. The results of the meta-regression analysis for muscle strength indicated larger benefits of chronic SS exercises in samples with higher proportions of female, older participants, and a higher number of repetitions per stretching exercise and session. For muscle power, results suggested larger gains for older participants. Regarding flexibility, findings indicated larger benefits following a higher number of repetitions per exercise and a longer time under stretching per session as well as a longer total time under stretching. 

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Chronic Effects of Static Stretching Exercises on Muscle Strength and Power in Healthy Individuals Across the Lifespan: A Systematic Review with Multi-level Meta-analysis

Flexibility is a measurable physical capacity considered as a key component of physical fitness. Poor flexibility is usually attributed to excessive tension exerted by the antagonist muscles of the movement and, supported by weak scientific evidence, passive stretching is considered as the most effective intervention in the promotion of the muscle extensibility, in attempting to improve mobility. The proposal of this paper is a review of the effects of static stretching in human movement and a presentation of strength training as a more robust alternative based on scientific evidence. First, we try to define which factors influence the ability of the human body to move into their functional safety range of motion. Second, we present a critical scientific literature review of the effects of static stretching in the promotion of range of motion, injury prevention, and sports performance. Third, we propose alternatives to static stretching such as proprioceptive neuromuscular facilitation, dynamic stretching, and especially strength/resistance training, in the promotion of a better range of motion. Finally, we conclude that perhaps problems of flexibility/mobility should not be addressed with static processes, but with movement.

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João Moscão

Papers

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

A review of the effects of static stretching in human mobility and strength training as a more powerful alternative: Towards a different paradigm