Skeletal muscle characteristics in children 9-15 years old: force, relaxation rate and contraction time.

Relaxation rate (RR), half contraction time to tetanus (CTT1/2) and force-frequency curves were investigated in 77 children, aged 9-15 years, using supramaximal stimulation of the ulnar nerve and recording from the adductor pollicis muscle. No sex differences were found in these variables. The RR was independent of age and similar to that in adults. The CTT1/2 was least at the age of 15. The only age-dependent parameter in the force-frequency curves was the relative force developed at a stimulus frequency of 10 Hz, which increased with increasing age. A fatiguability test was performed in 25 children. Reference values for the different parameters are given.