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

Abstract

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 postactivation potentiation. Men had higher MVC force than boys and post-pubertal boys higher than prepubertal 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.

Age-Related Changes in Twitch Properties of Plantar Flexor Muscles in Prepubertal Children

“…Considering that the time course of a twitch elicited in vivo informs about the muscle fibre type distribution (23,24), the triceps surae fibre type distribution seems to be the same for prepubertal children between 7 and 11 years. These results were also found when comparing CT and HRT values of the twitch of the triceps surae between prepubertal and postpubertal children (1)(2)(3)(4).…”

“…It is now well-established that during growth, muscles become stronger (1)(2)(3)(4) and this increase in strength is associated with changes in body and muscle sizes (2,5,6).…”

“…This was performed to compare contractile properties of skeletal muscles between prepubertal and postpubertal children (1,2) or between children (prepubertal and postpubertal) and adult subjects (4,7). It has been shown that twitch force increased with age (1)(2)(3)(4) and that this increase was related to the increase in muscle size (2).…”

“…This was performed to compare contractile properties of skeletal muscles between prepubertal and postpubertal children (1,2) or between children (prepubertal and postpubertal) and adult subjects (4,7). It has been shown that twitch force increased with age (1)(2)(3)(4) and that this increase was related to the increase in muscle size (2). Furthermore, no significant difference in the time course of the twitch (contraction time and half relaxation time) was reported between prepubertal and postpubertal children (1)(2)(3)(4), which suggests that the fiber-type composition of the muscles was already adult-like.…”

Theoretical Background and Practical Applications of the Physiological Mechanism of Post-Activation Potentiation

“…For instance although children and adults demonstrated similar PAP levels in terms of twitch torque (Pääsuke, 2000), children are not able to improve their jumping performance as adults do after a conditioning stimulus (Arabatzi et al, 2014). This indicates that deterioration in technique could mask the PAP effect, especially immediately after the conditioning stimulus when the fatigue effect is more prominent.…”