Twitch contraction properties of plantar flexor muscles in pre- and post-pubertal boys and men

This study compared electrically evoked twitch contraction characteristics of the plantar flexor muscles in pre-pubertal (11-year-old) and post-pubertal (16-year old) boys, and young (19- to 23-year-old) men. The posterior tibial nerve was stimulated by supramaximal square-wave pulses of 1 ms duration at rest and after brief (5 s) isometric maximal voluntary contraction (MVC) of the plantar flexor muscles, i.e. during post-activation potentiation. Men had higher MVC force than boys and post-pubertal boys higher than pre-pubertal boys. Pre-pubertal boys had lower peak twitch forces (P _t) at rest and when potentiated compared with post-pubertal boys and men, whereas no significant differences were found between post-pubertal boys and men. Pre-pubertal boys had higher ratios of P _t at rest and potentiated P _t to MVC force than post-pubertal boys and men. No age-related differences were obtained in post-activation potentiation, rest and potentiated twitch contraction and half-relaxation time, and MVC force relative to body mass. The main findings of the study were that puberty is characterized by increased muscle force-generating capacity with no change in twitch potentiation and time-course characteristics, and that twitch force-generating capacity develops in an adult-like pattern after puberty. Accepted: 10 April 2000