Temperature‐dependent transitions in isometric contractions of rat muscle.

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Abstract
The effect of temperature on tetanic tension development was examined in extensor digitorum longus (fast-twitch) and soleus (slow-twitch) muscles of the rat, in vitro and with direct stimulation. The temperature range was from 35-10.degree. C. The maximum tetanic tension decreased slightly on cooling from 35-25.degree. C. Cooling below 20.degree. C resulted in a marked depression of tetanic tension. The results were similar in the 2 muscles. Analysis (in the form of Arrhenius plots) of the rate of tetanic tension development and relaxation clearly showed the occurrence of 2 phases in their temperature dependence, due to an increased temperature sensitivity below about 25.degree. C. Arrhenius activation energy estimates for temperatures lower than 21.degree. C were around twice as high as those for temperatures higher than 24.degree. C in both muscles.