EFFECTS OF TEMPERATURE ON THE MAXIMAL INSTANTANEOUS MUSCLE POWER OF HUMANS

The maximal instantaneous muscle power (w(i, max)) probably reflects the maximal rate of adenosine 5'-triphosphate (ATP) hydrolysis (ATP(max)), a temperature-dependent variable, which gives rise to the hypothesis that temperature, by affecting ATP(max), may also influence w(i, max). This hypothesis was tested on six subjects, whose vastus lateralis muscle temperature (T(muscle)) was monitored by a thermocouple inserted approximately 3 cm below the skin surface. The W(i, max) was determined during a series of high jumps off both feet on a force platform before and after immersion up to the abdomen for 90 min in a temperature controlled (T = 20 +/- 0.1-degrees-C) water bath. Control T(muscle) was 35.8 +/- 0.7-degrees-C, with control W(i, max) being 51.6 (SD 8.7) W.kg-1. After cold exposure, T(muscle) decreased by about 8-degrees-C, whereas w(i, max) 27% lower. The temperature dependence of W(i, max) was found to be less (Q10 < 1.5, where Q10 is the temperature coefficient as calculated in other studies) than reported in the literature for ATP(max). Such a low Q10 may reflect an increase in the mechanical equivalent of ATP splitting, as a consequence of the reduced velocity of muscle contraction occurring at low T(muscle).