Effect of temperature on the contractile properties and muscle power of triceps surae in humans.

The effects of heating and cooling on the electrically evoked mechanical and contractile properties of the triceps surae in relation to the maximal dynamic performance of the leg muscles during cycling and vertical jumping have been examined in five healthy male subjects. A mean rise of 3.1 degrees C in muscle temperature (Tm) was associated with a decrease in time to peak tension (TPT) and half-relaxation time (1/2RT) but was without effect on twitch (Pto) and tetanic tension at 20 Hz (Po20) and 40 Hz (Po40) and maximal voluntary contraction (MVC). Reducing Tm by 8.4 degrees C had the opposite effect on TPT and 1/2RT and produced a fall in Pto, Po40, and MVC. The peak power output during cycling (W1) and jumping (W) was linearly related to Tm as well as negatively associated with TPT. The best single guide to W and W1 was given by a ratio of MVC to TPT: W (W) = 626.5 + 79.04 (MVC/TPT)(N/ms; r = +0.82) and W1 (W) = 1,342 + 84.9 (MVC/TPT)(N/ms; r = +0.87). The results underline the importance of the contractile and force generating capacity of human muscle in determining maximal power output and performance during exercise of a few seconds duration.