Exercise Timing and Circadian Rhythms

Abstract

Circadian rhythms and exercise physiology are intimately linked, but the symbiosis of this relationship has yet to be fully unraveled. Exercise exerts numerous health benefits from the organelle to the organism. Proper circadian function is also emerging as a prerequisite for maintaining health. The positive effects of exercise on health may be partially mediated by an exercise-induced change in tissue molecular clocks and/or the outcomes of exercise may be modified depending on when exercise is performed. This review provides a brief overview of circadian biology and the influence of exercise on the molecular clock, with an emphasis on skeletal muscle. Additionally, we provide considerations for future investigations seeking to unravel the mechanistic interactions of exercise and the molecular clock.

Keywords: Circadian Rhythms; Exercise Physiology; Time-of-day.

Figure 1.. Conceptual cartoon depicting links between the molecular clock and tissue-specific clock controlled gene expression.

Bmal1 and Clock direct the transcription of clock-controlled genes including Periods and Cryptochromes, which in turn form a heterodimer to repress activity of BMAL1 and CLOCK and maintain an approximate 24h rhythm of gene expression. In coordination with tissue-specific transcription factor(s) (ts-TF), BMAL1 and CLOCK direct the transcription of clock-controlled genes. This oscillating gene expression output from the molecular clock directs a daily program of transcription that impacts cellular physiology and metabolism.