Abstract

Diurnal, ultradian, and circadian rhythms tend to govern the secretion patterns of hormones. Since few hormonal responses are truly circadian (regulated by no external stimulus) in nature, several factors such as sleep-wake cycles, nutrition, meal timing, exercise, other hormones, and stress can alter diurnal (daily) rhythm patterns. It is precisely for this reason that competitive and recreational athletes and their coaches should be aware of these cycles and related hormonal interactions as well as the individual hormonal effects of exercise. The athlete should strive to establish a set daily pattern in order to ensure regulated and optimal levels of anabolic hormones and growth factors.