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Background: Over the past decades, an exponential growth has occurred with regards to the number of scientific publications including meta-analyses on youth resistance training. Consequently, it is timely to summarize findings from meta-analyses in the form of an umbrella review.
Introduction to Report: Despite previous misconceptions on the effectiveness and safety of youth resistance training, more recent studies show convincing evidence of resistance training on markers of performance and health in healthy children and adolescents, if appropriately prescribed and supervised.
Fourteen meta-analyses were included in this umbrella review. Eleven of these meta-analyses reported between- subject effect sizes which are important to eliminate bias due to growth and maturation. Resistance training produced medium-to-large effects on muscle strength, small-to-large effects on muscle power, small-to-medium effects on linear sprint, a medium effect on agility/change-of-direction speed, small-to-large effects on throwing performance, and a medium effect on sport-specific enhancement.
Results: This systematic umbrella review aimed to provide an over-view of the effects of resistance training on proxies of physical fitness in healthy children and adolescents. The main findings of this umbrella review are: 1- Resistance training has medium-to-large effects on measures of muscle strength, small-to-large effects on muscle power, small-to-medium effects on linear sprint speed, a medium effect on agility/change-of-direction speed, small- to-large effects on throwing performance, and a medium effect on sport-specific performance; 2- There are few consistent findings from the included meta-analyses regarding the moderating effects of age, maturation, sex, expertise level, and/or resistance training type on muscle strength and muscle power, and 3- The included meta-analyses are of low-to-moderate methodological quality and the presented evidence is of low or even very low quality.
Effects of Resistance Training on Physical Fitness in Healthy Youth: This umbrella review indicates that resistance training interventions can enhance physical fitness in children and adolescents beyond a level which is not exclusively achievable from growth and maturation. It was found that the effects of resistance training on measures of muscle strength and power were small-to-large in magnitude, with small-to-medium effects for secondary outcomes including linear sprint speed, agility/change-of-direction speed, and sport-specific performance.
This umbrella review identified current gaps in the literature and suggests that future resistance training research should consistently report data on participants’ maturational status.