Muscle Strength Reference Values and Correlation with Appendicular Muscle Mass in Mexican Children and Adolescents.

Strength and muscle mass are important determinants of health status, and reference values for pediatric populations from every country or geographic region are needed. The aim of this study was to develop age- and sex-specific reference values of muscle strength and evaluate the correlation between muscle strength and appendicular lean mass in Mexican children and adolescents. A cross-sectional study was conducted in 1111 healthy subjects ages 5 to 19 years of age participating in the "Body Composition Reference Values in Mexican Children and Adolescents" study. Smoothed reference values for the 1, 3, 5, 15, 25, 50, 75, 85, 95, 97, and 99 percentiles of muscle strength for upper and lower limbs were developed based on age and sex using Jamar® and Microfet2® dynamometers. Mean values were derived using the Generalized Additive Models for Location, Scale and Shape (GAMLSS), and lean mass was determined using dual-energy X-ray absorptiometry. Highly positive correlations of muscle strength with lean mass in upper limbs were found r-values 0.87-0.92 for boys and r = 0.80-0.86 for girls. High and moderate positive correlations for lower limbs were also noted for upper limbs: r = 0.74-0.86 for boys and r = 0.67-0.82 for girls. The reference values for appendicular muscle strength established in this study demonstrated a high and positive correlation between appendicular mass and muscle strength. These data will be useful when evaluating conditions and diseases affecting muscle or sports.