Methodological quality of meta-analyses on resistance training to improve hypertrophy and strength in healthy young adults: An umbrella review

Objectives. - The review of systematic reviews with meta-analyses is a scientifically important procedure for performing a qualitative analysis of published works. Thus, the objectives of this study were to systematically review the meta-analytic evidence verifying the effects of resistance training on muscular strength and/or hypertrophy in healthy adults and to address the quality of the meta-analytic evidence (CRD42020188928). News. - Systematic reviews with meta-analyses that verified the effects of resistance training on strength and/or hypertrophy in healthy young adults, published in English, were searched in the PubMed, Web of Science, and Cochrane databases. The searches resulted in 1915 references, and 19 references were included following the adopted criteria. The selected meta-analyses investigated a total of 587 randomized controlled trials - 159 evaluated strength, 160 hypertrophy, and 268 both outcomes, involving 12,375 subjects of both sexes. Of the 19 selected meta-analyses, 31.6% verified the effect size of muscle strength, 31.6% of hypertrophy, and 36.8% of both variables (strength and hypertrophy). Moderate correlations were observed in the AMSTAR 2 quality assessment with the assessment of the quality of evidence (0.64; P = 0.003) and with the year of publication of the studies (0.57; P = 0.03). The GRADE assessment indicated very low to high quality of evidence.