What role does ACTN3 play in Müdigkeit?

ACTN3 (alpha-actinin-3) is primarily known for its role in muscle function, especially fast-twitch (type II) fibers. The common R577X polymorphism results in a complete lack of ACTN3 protein in XX genotype carriers. This is associated with reduced sprint and power performance, but possibly better endurance. Regarding fatigue (Müdigkeit), there is no strong direct evidence. Some studies suggest that ACTN3-deficient individuals (XX) may experience altered muscle fatigue profiles, possibly due to a metabolic shift toward oxidative pathways. However, the effects are small and heavily influenced by training, sleep, and nutrition. A DNA test for ACTN3 alone is not useful for predicting or managing fatigue. Evidence level: human-observational/moderate. Caveat: most studies are in athletes; general population relevance is limited.