The force‐velocity relation of rat fast‐ and slow‐twitch muscles examined at different temperatures.

Abstract

The steady-state force-velocity relation was examined at temperatures between 35.degree. and 10.degree. C in rat fast-twitch (extensor digitorum longus, e.d.l.) and slow-twitch (soleus) muscle preparations in vitro, with direct stimulation and employing the isotonic release technique. The curvature of the force-velocity relation increased with cooling in both muscles; the increase was more pronounced below 25.degree. C. The maximum shortening velocity of e.d.l. muscle decreased with a Q10 (temperature coefficient) of 1.8 in cooling from 35.degree.-25.degree. C; it decreased with a Q10 of 2.4 in cooling below 20.degree. C. The shortening velocity of slow muscle was more temperature sensitive. The Q10 values for soleus muscle were 2.0 at 35.degree.-25.degree. C and 3.5 below 20.degree. C. The maximum rate of isometric tetanic tension rise had a temperature sensitivity similar to the maximum velocity of shortening in each muscle type.