Review
Resistance training to improve power and sports performance in adolescent athletes: A systematic review and meta-analysis

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Abstract

Objectives

Resistance training in untrained adolescents can positively effect health-related fitness as well as improve muscular power and sports performance. The impact of resistance training on adolescent athletes is less clear. The purpose of this review is to determine the effectiveness of resistance training programs on muscular power and sports performance in adolescent athletes.

Design

Systematic review and meta-analysis of previously published studies investigating resistance training in adolescent athlete populations.

Methods

A systematic search of Medline, Embase, and SPORTDiscus databases was conducted on 21st March 2011 to identify studies evaluating resistance training programs on power and sports performance in adolescent athletes.

Results

Thirty-four studies were identified. All but two of the studies reported at least one statistically significant improvement in an alactic muscular power outcome. The most common indicators of alactic power were vertical jump (25 studies) and sprint running (13 studies) performance. Fourteen studies provided data to allow for pooling of results in a meta-analysis. A positive effect was detected for resistance training programs on vertical jump performance (mean difference 3.08 [95% CI 1.65, 4.51], Z = 4.23 [P < 0.0001]).

Conclusions

There is sufficient evidence to conclude that resistance-training interventions can improve muscular power in adolescent athletes. A positive effect on sports performance attributable to participation in resistance training was reported by almost half the included studies, however limited objective evidence to support these claims was found. Improvements in motor performance skills, such as jumping, are widely stated as indicators of improvements in sporting performance.

Introduction

The use of resistance training (RT) by children and adolescents has attracted increased interest as a means to improve health- and performance-related fitness components. The National Strength and Conditioning Association (NSCA) defines RT as a specialised form of conditioning involving the progressive use of a wide range of resistive loads and a variety of training modalities designed to enhance health, fitness, and sports performance.1 Numerous reviews and position papers published by advisory bodies have dispelled previous concerns regarding the safety and efficacy of RT for children and adolescents.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12

RT in children and adolescents is reported to have beneficial effects on: muscular strength and power1, 5, 6, 9, 10, 12; prevention and rehabilitation of injuries1, 5, 9, 10; long-term health1, 5, 11; cardiovascular fitness1, 5, 11; body composition;1, 5, 11 bone mineral density1, 5, 11; blood lipid profiles1, 5, 11; and self-esteem, depression and mental health.1, 5 The NSCA reports strength gains of approximately 30% are typically observed after appropriately designed and supervised short-term RT programs undertaken by children and adolescents.1

RT may also benefit sports performance.1, 5, 10, 11 Explosive muscular power and rate of force production are the basis for most sporting actions.13, 14 Speed and power are essential characteristics needed for successful performance in a large range of sports.15 It has been theorised that increases in the muscular strength and power levels of adolescents after participation in RT may improve sporting performance,1, 5, 11 but there is little direct evidence to conclude that increases in muscular strength and power alone will improve adolescent sporting performance.5, 10 Increases in strength and power after RT in both pre-adolescents and adolescents are usually attributed to increased neuromuscular activation and coordination rather than muscle hypertrophy.1, 5, 10, 11, 12, 16 Improvements in motor performance skills are also reported to contribute to increases in strength.1, 10, 11 Researchers commonly use motor performance skill tests such as horizontal and vertical jumps and sprint times to assess changes in muscular strength and power.1 These tests are practical, cost-effective tools to assess muscular power.14, 17, 18, 19, 20 A recent investigation of the intra-session and inter-session reliability of three devices commonly used to measure vertical jump height revealed an adequate level of reliability (intra-session reliability: ICC 0.92–0.95 and CV% 3.3–5.5%; inter-session reliability: ICC 0.84–0.90 and CV% 5.3–6.3%).21 The authors highlighted the importance of test familiarisation procedures and protocols including multiple jump attempts, to attain reliable results.21 Despite a lack of clear evidence supporting the association between measures of motor performance and improved adolescent sports performance, the results of motor performance tests are often used to infer subsequent improvements in sports performance.17

A recent review by Behringer et al. [55] concluded that RT is effective for improving motor performance in children and adolescents. Most of these participants had no athletic background (66%) and many studies included both children and adolescents. No previous review has summarised the potential of RT to improve muscular power and sports performance in adolescent athletes. Consequently, the primary aim of this systematic review and meta-analysis is to determine the effectiveness of RT programs on muscular power in adolescent athlete populations. A secondary aim is to determine the effectiveness of RT programs on adolescent sports performance.

Section snippets

Methods

The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement22 guided the conduct and reporting of this review. A systematic search of three electronic databases (Medline, Embase, and SPORTDiscus) was conducted on the 21st March 2011. In consultation with a librarian, search strategies were developed for the different databases. Articles published in English and in peer reviewed journals were considered for the review. No year restriction was placed on the search.

Results

The flow of studies through the review process is reported in Fig. 1. Sixty-two full-text articles were assessed; 34 met the inclusion criteria (Supplementary Table 2); and 14 studies were included in the meta-analysis.

The total number of participants in the included studies was 1070. Intervention participant numbers were 862 and control participant numbers were 208. Of the included studies: 21 assessed only males17, 18, 19, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42

Discussion

The primary aim of this systematic review was to determine the effectiveness of RT interventions on muscular power in adolescent athletic populations. Despite considerable heterogeneity in terms of study design and types of training, there is sufficient evidence to conclude that RT interventions have the potential to improve muscular power in adolescent athletes. All but two of the studies reported at least one statistically significant improvement in an alactic muscular power outcome. The most

Conclusions

RT interventions can improve the muscular power and motor skill performance of adolescents and subsequently may improve sporting performance.1, 5, 11, 55 This review investigated 34 RT intervention studies in adolescent athletic populations. While it has not been established which types of programs are most suitable for increasing muscular power and improving sporting performance in various adolescent athlete subgroups, RT, plyometric training, speed training or combinations of these training

Practical implications

  • Future studies should focus on improving study design and reporting features. Researchers should attempt to conduct randomised controlled trials and clearly describe their process of randomisation.

  • Authors are also encouraged to report statistical power calculations and effect sizes of observed changes.

  • Familiarisation with the assessments to be used is also recommended, particularly for vertical jump assessment.

  • Improvement in the description of the training interventions employed and clear

Acknowledgements

The authors of this study would like to thank the authors who responded to requests to provide additional information for the meta-analysis. No external funding was used for this project.

The authors have no competing interests relating to the content of this manuscript. There were no other contributors to this manuscript.

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