Myths vs facts: CLOCK and Sport

The CLOCK gene family regulates circadian rhythms, influencing sleep-wake cycles, hormone release, and metabolism. In sports, myths often exaggerate its role: some claim that specific CLOCK variants directly determine athletic performance. In reality, studies show modest associations between CLOCK polymorphisms (e.g., rs1801260) and time-of-day performance, such as strength or endurance tasks. However, effect sizes are small and heavily confounded by sleep quality, training status, and nutrition. Another myth is that the circadian clock is genetically fixed. Fact: light exposure, meal timing, and regular exercise can modulate CLOCK gene expression. The evidence is mostly mechanistic and from animal models; large human athlete studies are lacking. Thus, individual recommendations remain limited. For athletes, consistent sleep hygiene is far more impactful than testing CLOCK variants. Beware of marketing that oversimplifies gene-performance links.