Biological maturation, fat mass and cardiorespiratory fitness in prepubescent girls: A mediation analysis.

Background: The association between indicators of maturation and measures of physical fitness are not well correlated and vary according to chronological age, sex, body size, and motor characteristics. It is known that chronological age, maturation, and fat mass are significant predictors of cardiorespiratory fitness in girls, however, the contributions of fat mass to the relationship between maturation and endurance performance are still unclear.

Objective: The current study aimed to examine whether the association between somatic maturation and running performance in the 20-m shuttle-run in girls is mediated by estimated fat mass.

Methods: The sample comprised 67 girls, aged 8.00-8.99 years. Stature, body mass, and skinfolds were measured. Estimates of body composition and predicted mature stature (PMS) were then calculated. Current stature was expressed as a percentage of PMS and somatic maturation was given by z-scores of the percentage of PMS. Mediation analysis was performed using the bias-corrected bootstrap approach with 5000 resamples in order to obtain estimates of total, direct, and indirect effects of z-scores of the percentage of PMS on 20-m shuttle-run performance mediated by fat mass.

Results: The results show that fat mass mediated the negative effect of biological maturation on 20-m shuttle-run performance in the observed sample of prepubescent girls (Indirect effect: β = -0.177, 95%CI: -0.291 to -0.059).

Conclusion: Although the participants were prepubescent girls, poorer aerobic running performance appeared to be partly due to increased levels of fat mass.