Tanner stage is associated with testosterone level [33]. Serum testosterone level
is positively related to maximal isokinetic knee extension in adolescent boys [21]. In addition, voluntary activation level during http://www.selleckchem.com/products/Cisplatin.html maximal voluntary contraction [37,38], and proportion of fast type fiber [39] have been shown to be higher with increasing age. These findings will support the assumption that muscle quality might be higher in pubescent than in prepubescent boys, as hypothesized at the start of this study. However, this assumption is canceled by the current result that there was no significant difference between the prepubertal and pubertal groups in TQ/MV, with only a trivial or small effect size being observed. We should
comment on methodological issues with the estimation of muscle volume. The muscle volume was estimated using the prediction equation reported by Miyatani et al. [35], which has been derived from adult population. It has been shown that pennation angle, fascicle length relative to muscle length, and ratio of synergist muscle to total muscle volume is not different between prepubescent children and adults in the knee extensors [40] and ankle plantar flexors [13]. This implies that in an age span from childhood to adulthood, growth change in muscle volume is not associated with fascicle arrangement. In other words, the muscle thickness and limb length of children will be considered to be a scaled-down geometry of those in adults, and so the prediction equation derived from adult population can be used to estimate muscle volume for children. However, Midorikawa et al. [41] reported that while the muscle thickness-based prediction equation for adults are useful for estimating total and regional skeletal muscle mass for adolescents (Tanner stageā„II), this equation underestimates muscle mass in prepubescent children. If the previous finding can be applied to our data, the TQ/MV might be higher in the prepubertal
group than in the pubertal group due to the underestimation of MV in the prepubertal group. However, the current result refutes this. In the knee extensors, on the other hand, Anacetrapib the y-intercept of the regression line in the relationship between TQ and MV was significantly different from zero, but not for the ankle plantar flexors. This indicates that the higher y-intercept of the regression line from zero appears to result in the overestimation of the TQ/MV in the knee extensors in both groups. It is unknown whether this is due to the use of the prediction equation derived from an adult population. However, it should be noted that the significant difference in the y-intercept of the regression line from zero was found in both prepubertal and pubertal groups. In addition, the y-intercepts and slopes of regression lines in the corresponding relationships were similar between the two groups.