Physical exercise at a specific time-of-day and hormonal responses

Sports performance usually peaks in the late afternoon coinciding with the circadian peaks of body temperature. Moreover, increased nerve conduction velocity, joint suppleness, increased muscular blood flow, improvements of glycogenolysis and glycolysis, increased environmental temperature, and preferential meteorological conditions may all contribute to the circadian rhythm of physical performances. However, the typical circadian variation of physical performances can be blunted by a repeated-morning resistance training protocol. In this context, recent researches confirm the time-of-day specific training adaptation. Indeed, subjects who regularly trained in the morning hours improve their physical performance greatly at this time-of-day. However, subjects who regularly trained in the afternoon hours experience the greater training induced adaptation in the afternoon/evening. Hormones, such as testosterone and cortisol, have repeatedly been linked with resistance training adaptation. For instance, higher testosterone concentrations appear preferential. Testosterone and cortisol concentrations are higher in the morning. The morning elevated T level (seen as beneficial to achieve muscle hypertrophy) may be counteracted by the morning elevated C level and, therefore, protein degradation. Although T levels are higher in the morning, an increased resistance exercise-induced T response has been found in the late afternoon, suggesting greater responsiveness of the hypothalamo-pituitary-testicular axis then. Current knowledge suggest that athletes are advised to coincide training times with competition times, and (b) individuals may experience greater hypertrophy and strength gains when resistance training protocols are programmed in the afternoon for grater anabolic hormones' responses (e.g., Testosterone, IGF-1, etc.).