The development of muscle function from childhood to adulthood

Abstract

The quality of movement is determined in part by the force velocity relationship of the muscle involved. Conflicting results have been reported in studies comparing this relationship in adults and children due mainly to the variety of scaling techniques employed. These two studies examined the force-velocity and power-velocity relationships of the quadriceps muscles of children and adults using results scaled for local muscle size. Measurements of muscle function were collected using the Con-Trex isokinetic dynamometer. In study one twenty adults and twenty children performed maximal effort knee extensions at nine different velocities. Study two repeated the methodology of study one with three groups of equal gender distribution: children aged 6 years (n=20), 10 years (n=20) and young adults (n=20). Both studies scaled power values for lean thigh volume which was calculated using previously validated anthropometric measurements. The mean force-velocity curves showed a predictable shift upwards in the curves with each ascending age group in both studies. No gender difference was observed in the children’s groups but adult males achieved superior scores than female adults. The curves remained different following corrections of torque for CSA and velocity for length. ANOVA revealed significant differences in the uncorrected values of power between the two groups in study one and three groups in study two. When power values were corrected for lean thigh muscle volume, no significant differences were found between the groups in study one however this correction only yielded no differences between six year old boys and girls and 10 year old males. Despite these corrections for muscle size 10 year old females and, male and female adults all exhibited significantly higher power values at all ten velocities. Results in study two also revealed a significant mechanical advantage in the angle of peak torque for females’ age 10 years. The findings for study one suggest that differences in muscle strength between children and adults are a function of muscle size and imply that muscle function remains relatively unchanged from childhood to early adulthood. However the results of study two are not consistent with this assertion. Results of this study suggest that quantitative differences do not entirely account for the differences in the power velocity curves. The question as to whether there are qualitative differences in the muscle of children and adults remains open. Future studies should preferably be longitudinal in nature and examine known covariates while simultaneously using appropriate scaling techniques.