Detecting an athletes’ biorhythms through MEQ’s, hormone panels, and normal sleep–wake patterns allows practitioners to optimize training through diurnal specific protocol alterations. As such, recognizing that "time-of-day" only partially captures this phenomenon emphasizes the importance of considering an athletes’ internal clock when planning training . Understanding these chronotype-specific hormonal and thermoregulatory patterns allows practitioners to better align training protocols with an athlete’s biological rhythms, enhancing performance and recovery. Some researchers have also pointed out that ‘time-of-day’ is an exogenous effect and therefore, reflects only part of the picture when analyzing an individual’s circadian-related physiology and performance. Regarding performance, it has been suggested that an individual’s skeletal muscle-specific circadian clock is a mediator of strength and physical performance .
Age and season were identified as predictors of the baseline testosterone levels. The simulations also evidence that a fast decrease in the testosterone levels occurs after the testosterone peak. Both models predict similar patterns with higher testosterone peaks early during the morning and nadir levels during the afternoon and evening. Effectively, in a study conducted in Norway, these authors observed that free testosterone levels showed a significant seasonal pattern (P 25).
The circadian rhythm of the testosterone was described by a stretched cosine function. Moreover, many clinical studies are subjected to small sample sizes, and most studies are cross-sectional, lacking long-term follow-up investigations evaluating the long-term effects of clock gene variations on testosterone levels. Second, testosterone synthesis is regulated by the peripheral circadian clock, and by the SCN through the hypothalamic–pituitary–testis axis. Accordingly, the importance of clock genes in the occurrence and development of male diseases is becoming increasingly prominent.
Here we review the central and peripheral regulatory mechanisms underlying the influence of circadian clock genes upon testosterone synthesis. The circadian clock is an important internal time regulatory system for a range of physiological and behavioral rhythms within living organisms. Moreover, Bmal1 knockdown inhibited testosterone level by inducing apoptosis of Leydig cells (111), and the circadian clock system was involved to the process of bisphenol A (113) and zearalenone (114) reducing testosterone production. Since then, most of the core clock genes like Bmal1, Per1/2/3, Cry1/2, Rev-erbα/β, Rorb, and Dbp in Leydig cells were demonstrated to rhythmically oscillate (101–103, 109), except Clock, Rora, Ck1δ, and Ck1ε (102).
Time-restricted eating—consuming all meals within a consistent 8–10 hour window during daylight—has been shown to support hormonal balance and improve testosterone in overweight men . Light is the primary signal that regulates your circadian clock. Disruptions in your sleep-wake cycles, light exposure, meal timing, and stress response can all blunt testosterone synthesis.
In order to maintain alignment with the 24-hour rotation of the planet, the master clock must adjust by about 12 to 18 minutes every day. In most adults and adolescents, this master clock operates on a cycle that’s slightly longer than 24 hours. Circadian rhythms affect many bodily processes, your mental state, and your behavior. While this paper takes a broad approach to the terms "sport" and "exercise performance", future work should address how specific sports, roles, and positions might uniquely respond to circadian factors.