Exercise reverses photoperiodic anestrus in golden hamsters.

In contrast to the inhibitory effects of endurance exercise on reproductive function in women athletes, voluntary running induces estrous cyclicity in anestrous female hamsters maintained in the nonstimulatory short-day photoperiod. Increased concentrations of circulating prolactin (Prl) seen in these animals are not responsible for the reversal of photoperiodic anestrus as demonstrated by experimental manipulations of prolactin secretion. Voluntary running also facilitates growth hormone (GH) release and somatic growth in hamsters independently of the photoperiod. Thus, it appears that endurance exercise can have facilitatory as well as inhibitory effects on the reproductive function in female mammals.