Somato-Vegetative Interaction at the Peripheral Level: Possible Effects on Motor Performance

Data are available in the literature that demonstrate the relationship between skeletal muscle function and sympathetic nervous system activity. Exercise has been associated with an increase in sympathetic outflow, which is aimed at adjusting cardio-respiratory parameters to meet the requirements of the active muscle. Such an increase can be obtained either through the coactivation of sympathetic and motor systems, induced by central parallel commands (Krog and Lindhard 1913; Goodwin et al. 1972; McCloskey 1981) or through a reflex activation mediated by group III and group IV muscle afferents excited by the muscular contraction (McCloskey and Mitchell 1972; Iwamoto et al. 1991). These changes of the sympathetic command could subserve motor performance not only by modifying the vegetative functions but also by affecting the activity of skeletal muscle through an action exerted at both central and peripheral levels. The present paper does not deal with the role played by the central monoaminergic pathway in motor control but focuses on the possibility that an increase in sympathetic outflow affects skeletal muscle function by acting at the peripheral level. In particular, the possibility is considered that an increase in the sympathetic outflow induces (a) a change in muscle spindle information thereby reflexly modifying muscle function and (b) a change in muscular contraction.