Temperature and the Force-Velocity Relationship of Live Muscle Fibres from the Teleost Myoxocephalus Scorpius

Abstract

Small bundles of fast fibres were isolated from the myotomal muscle of the teleost Myoxocephalus scorpius. The temperature-dependence of isometric contractile properties and the force-velocity (P-V) relationship were studied. Fibres were found to deteriorate above 18 °C, and the force plateau during tetanic stimulation was not maintained above 15°C. Twitch and tetanic tension (Po) showed optima at around 8 °C. Force-velocity curves were fitted using either Hill’s hyperbolic equation or a hyperbolic-linear equation (hyp-lin). The best fit to the data was provided by the hyp-lin equation, which gave consistently higher values for unloaded contraction velocity (Vmax): 4·3, 8·1 and 9·5 muscle lengths s-1 at 1,8 and 12 °C, respectively. The P-V relationship was found to become progressively more curved at higher temperatures. Muscle power output calculated from the hyp-fin equation was 123 W kg-1 at 1°C and 256 W kg-1 at 8 °C. Curves normalized for Po and Vmax at each temperature show that the change in curvature is sufficient to increase the relative power output of the muscle by around 15 % on decreasing the temperature from 8 to 1 °C.