Total and regional skeletal muscle mass references by sport participation and body size in youth

Skeletal muscle mass (SMM) is a relevant indicator of adolescent health influenced by sport participation, body size, and maturation. However, limited data are available from techniques accessible to field professionals. Purpose To provide reference data of regional and total-body SMM and fat-free mass (FFM) derived from anthropometry among groups of age, sex, and sport participation in healthy Caucasian children and adolescents. Materials and methods A cross-sectional dataset of 1,438 participants aged 8-18 years were analyzed for this study. Regional and total-body SMM and FFM were estimated from anthropometric variables. Sport participation was obtained by ad hoc questionnaires and maturity offset was calculated using predictive equations. General linear model of mixed factors was used to analyze the variance of FFM or SMM across groups and confounders. Ln-ln regression analysis was applied to describe the scaling relationship between SMM and height. Results Positive interactions were found between sex, sport participation, and age for regional muscle variables ( P <0.05). Adjusted total and regional SMM significantly increased along school-age periods in the active groups (∼2.2 kg gain, P <0.05, boys and girls; arm, ∼1.3 cm gain, P <0.01, boys), and allometric values were higher in boys than girls for regional muscle ( P <0.01). Discussion The novel contribution of this analysis includes regional indicators of SMM and the relevance of sport participation on SMM accrual in post-pubertal boys. Also, confirms that muscle growth rate varies across sex and phases of puberty, which arises a plausible sexual phenotype/dysmorphism of regional SMM influenced by sport participation.