Work Capacity of Muscles from Animals Treated with Male Sex Hormone

Abstract

Introduction. It has often been said that male sex hormone contributes to the strength of muscles and endurance of male animals. This conclusion, although possibly valid, has relatively little experimental evidence to support it, especially when individual muscles are considered. Hoskins in 1925 demonstrated that voluntary activity in normal rats was about 60 per cent greater than in castrate rats. Gans and Hoskins in 1926 reported that isolated gastrocnemius muscles from castrate rats did approximately 25 per cent less work than similar muscles from normal animals. Hoskins in 1927 attempted to restore the activity of castrate animals with testis grafts but the results were negative. Gans and Hoskins (1926) determined that weights of individual muscles of castrate animals were greater than those from normal ones. Papanicolaou and Folk (1938) also reported hypertrophy in the muscles of guinea pigs after treatment with testosterone propionate. Wainman and Shipnounoff (1941) found that castration resulted in marked decrease in size of the striated perineal muscles but that these muscles could be restored to normal development by administering testosterone propionate. Simonson, Kearns, and Enzer (1941 and 1944) reported definite influences on endurance and performance in different types of work among eunochoid and castrate men treated with testosterone propionate and methyl testosterone. In normal men, however, Samuels, Henschel and Keys (1942) found no increase in work capacity after treatment with androgens. In 1945 Herrick reported that female fowls and capons treated with testosterone propionate showed approximately 30 per cent increase in the breaking strength of the gastrocnemius muscles and 100 per cent increase in the breaking strength of the skin. Chemical analyses revealed a greater amount of collagen in the tissues of treated birds.