Evidence check: CLOCK in the context of Sport

The CLOCK gene is a core component of the circadian rhythm machinery. In sports, variants in CLOCK have been studied for their association with chronotype, optimal training timing, and injury risk. However, the evidence is moderate at best. While some GWAS and candidate gene studies report links to athletic performance (e.g., sprint or endurance), effect sizes are small and replication inconsistent. Lifestyle factors such as sleep hygiene, training schedule, and nutrition have a much larger impact. A direct-to-consumer DNA test for CLOCK variants alone cannot provide actionable training advice. It is not a substitute for assessing individual chronotype via validated questionnaires or actigraphy. The clinical utility remains unproven, and no specific supplementation or training modification is supported by current evidence. Caution: overinterpretation of such genetic results can lead to unnecessary changes in training routines.