The influence of temperature on the isometric characteristics of fast and slow muscle in the cat

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Abstract
The maximum tetanic tension (initial strength) and the length of time, 20, 40 or 60%, of that initial strength could be maintained (endurance) was assessed in 2 fast twitch muscles (the plantaris and the medial gastrocnemius) and a slow twitch muscle (the soleus) of the cat at muscle temperatures ranging between 22 and 38°C. The results of these experiments showed that the strength of the soleus was constant between muscle temperatures of 38 to 28°C, and then gradually decreased as the muscle was cooled further. Plantaris, on the other hand, showed a reduction in strength at all muscle temperatures less than 38°C; the response of the medial gastrocnemius was between these two extremes. The longest endurance for the soleus muscle was found to be at a muscle temperature of 28°C, the endurance being as much as 3 times higher at this temperature than at muscle temperatures of 22 or 38°C. The medial gastrocnemius showed a similar response but the endurance only doubled when comparing the endurance at a muscle temperature of 28 to 38°C. In contrast, the plantaris maintained a constant endurance over the temperature range of 38 ot 28°C; below this muscle temperature the endurance decreased markedly. The mechanism for this response appeared to be related to the effect of temperature on the contractile characteristics of the muscles.