Schematic representation of suggested child-adult differences in muscle contractility stemming from differential motor-unit activationparisons of size-normalized muscular force, velocity (solid lines), and power (dashed lines) relationships are shown
Table 1 summarizes the evidence presented in this review, indicating the likelihood of acknowledged muscle functional factors of accounting for the various known child-adult functional and metabolic differences. While some factors, notably muscle composition, can account for a considerable portion of the observed differences, only the differential motor-unit activation hypothesis can account for all of them. As illustrated in Figure 2 , children’s size-normalized maximal force, velocity, and power are all lower than the respective adult values. Moreover, the age-related difference in maximal velocity is greater than the respective difference in maximal force. As power is a product of force and velocity, children’s maximal power is further compromised, compared with adults, than either force or velocity.
Figure 2 provides a schematic graphic illustration of the proposed child-adult muscle-contractile differences, as would be manifested in force-velocity and force- power relationships
Numerous factors may be involved in many of the reviewed child-adult differences lovoo. As shown in Table 1 , these differences can largely or fully be explained by three main factors: muscle fiber composition, metabolic profile, and motor-unit activation. In some cases (e.g., children’s lower muscular power or greater endurance), the relative contribution of these factors cannot be untangled and the observed differences can be explained by any one, two, or all three factors. In other cases, it may be possible to dismiss metabolic profile differences, but neither of the other two factors (e.g., children’s lower instantaneous force or RFD). Continue reading This depiction is based on the evidence presented in this review, and notably that of Asai & Aoki (4)