ACTN3 in bodybuiders and powerlifters

Those who are likely endowed with a high proportion of fast twitch muscle fibers are less likely to have a nonsense variant of ACTN3, is what they find among a set of black and white bodybuilders and powerlifters. This gene has been investigated in several different populations looking at the association between it and the type of sport (sprint or endurance) that individuals excel at. The overall findings are mixed, but highly suggestive. If interested, I've posted on this gene many times before (you can do a search for actn3 in the search box for this blog - in the Blogger banner at the top)

The ACTN3 R577X nonsense allele is under-represented in elite-level strength athletes

Stephen M Roth, Sean Walsh, Dongmei Liu, E Jeffrey Metter, Luigi Ferrucci and Ben F Hurley

European Journal of Human Genetics Advance online publication

Abstract: Previous reports have shown a lower proportion of the ACTN3 X/X genotype (R577X nonsense polymorphism) in sprint-related athletes compared to the general population, possibly attributed to impairment of muscle function related to -actinin-3 deficiency. In the present study, we examined the frequency of the X/X genotype in both Black and White elite-level bodybuilders and strength athletes in comparison to the general population. A reference population of 668 Whites (363 men and 305 women) and 208 Blacks (98 men and 110 women) was genotyped for the ACTN3 R577X polymorphism. Strength athletes (52 white and 23 black; 4 women) consisting predominantly of world class and locally competitive bodybuilders, and elite powerlifters were recruited and similarly genotyped. Significantly lower X/X genotype frequencies were observed in the athletes (6.7%) vs controls (16.3%; P=0.005). The X/X genotype was significantly lower in White athletes (9.7%) vs controls (19.9%; P=0.018). No black athletes (0%) were observed with the X/X genotype, though this finding only approached statistical significance vs controls (4.8%; P=0.10). The results indicate that the ACTN3 R577X nonsense allele (X) is under-represented in elite strength athletes, consistent with previous reports indicating that -actinin-3 deficiency appears to impair muscle performance.