Association of the ACTN3 Genotype with Muscle Function: A Systematic Review and Meta-analysis.

The R577X polymorphism in the α-actinin-3 gene (ACTN3) influences the expression of α-actinin-3, and previous studies have reported its association with muscle strength and power performance. This systematic review and meta-analysis aimed to clarify the relationship between the ACTN3 R577X polymorphism and various indicators of muscle strength and power. A systematic search of PubMed and Web of Science was conducted on 15 October 2025, and studies were included if they were published in English, involved healthy human participants, assessed muscle function, and analyzed the ACTN3 R577X genotype. Muscle function outcomes examined in this review included maximum voluntary contraction, one-repetition maximum, isokinetic strength, jump performance, sprint performance, Wingate test, chair stand test, and walking test. Fifty-three articles were included in the meta-analysis. One-repetition maximum, maximum voluntary contraction and jump performance showed a significant association with the ACTN3 R577X polymorphism in the additive model and were higher for the RR, RX and XX genotypes (one-repetition maximum: p = 0.005, maximum voluntary contraction: p = 0.006, and jump performance: p = 0.003). There was no significant association between the ACTN3 R577X polymorphism and other measurements. This study suggests that the ACTN3 R577X polymorphism is associated with one-repetition maximum, maximum voluntary contraction, and jump performance in the additive model and the impact may be stronger among men.