ACTN3 genotype is associated with increases in muscle strength in response to resistance training in women

J Appl Physiol (1985). 2005 Jul;99(1):154-63. doi: 10.1152/japplphysiol.01139.2004. Epub 2005 Feb 17.


The alpha-actinin 3 (ACTN3) gene encodes a protein of the Z disk of myofibers, and a polymorphism of ACTN3 results in complete loss of the protein. The ACTN3 genotype (R577X) has been found to be associated with performance in Australian elite athletes (Yang N, MacArthur DG, Gulbin JP, Hahn AG, Beggs AH, Easteal S, and North K. Am J Hum Genet 73: 627-631, 2003). We studied associations between ACTN3 genotype and muscle size [cross-sectional area of the biceps brachii via magnetic resonance imaging (MRI)] and elbow flexor isometric (MVC) and dynamic [1-repetition maximum (1-RM)] strength in a large group of men (N = 247) and women (N = 355) enrolled in a 12-wk standardized elbow flexor/extensor resistance training program of the nondominant arm at one of eight study centers. We found no association between ACTN3 R577X genotype and muscle phenotype in men. However, women homozygous for the ACTN3 577X allele (XX) had lower baseline MVC compared with heterozygotes (P < 0.05) when adjusted for body mass and age. Women homozygous for the mutant allele (577X) demonstrated greater absolute and relative 1-RM gains compared with the homozygous wild type (RR) after resistance training when adjusted for body mass and age (P < 0.05). There was a trend for a dose-response with genotype such that gains were greatest for XX and least for RR. Significant associations were validated in at least one ethnic subpopulation (Caucasians, Asians) and were independent of training volume. About 2% of baseline MVC and of 1-RM strength gain after training were attributable to ACTN3 genotype (likelihood-ratio test P value, P = 0.01), suggesting that ACTN3 is one of many genes contributing to genetic variation in muscle performance and adaptation to exercise.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actinin / genetics*
  • Adaptation, Physiological / genetics
  • Adolescent
  • Adult
  • Asian Continental Ancestry Group / statistics & numerical data
  • Cohort Studies
  • European Continental Ancestry Group / statistics & numerical data
  • Exercise / physiology*
  • Female
  • Genotype
  • Humans
  • Male
  • Muscle Contraction / genetics*
  • Muscle, Skeletal / anatomy & histology*
  • Muscle, Skeletal / physiology*
  • Physical Exertion / physiology*
  • Polymorphism, Genetic / physiology
  • Sex Distribution
  • Sex Factors
  • United States / epidemiology


  • ACTN3 protein, human
  • Actinin