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Alpha-Actinin-3 (ACTN3) R577X Polymorphism Influences Knee Extensor Peak Power Response to Strength Training in Older Men and Women

¹ Department of Kinesiology, College of Health and Human Performance, University of Maryland, College Park.
² Department of Epidemiology, University of Pittsburgh, Pennsylvania.
³ Research Center for Genetic Medicine, Children's National Medical Center, Washington, D.C.
⁴ USDA, ARS, BHNRC, Diet and Human Performance Laboratory, Beltsville, Maryland.
⁵ Department of Aerospace Engineering, Space Systems Laboratory, University of Maryland, College Park.

Address correspondence to Ben F. Hurley, PhD, Department of Kinesiology, University of Maryland, College Park, MD 20742. E-mail: benhur{at}umd.edu.

Background. The alpha-actinin-3 (ACTN3) R577X polymorphism has been associated with muscle power performance in cross-sectional studies.

Methods. We examined baseline knee extensor concentric peak power (PP) and PP change with 10 weeks of unilateral knee extensor strength training (ST) using air-powered resistance machines in 71 older men (65 [standard deviation = 8] years) and 86 older women (64 [standard deviation = 9] years).

Results. At baseline in women, the XX genotype group had an absolute (same resistance) PP that was higher than the RR (p =.005) and RX genotype groups (p =.02). The women XX group also had a relative (70% of one-repetition maximum [1-RM]) PP that was higher than that in the RR (p =.002) and RX groups (p =.008). No differences in baseline absolute or relative PP were observed between ACTN3 genotype groups in men. In men, absolute PP change with ST in the RR (n = 16) group approached a significantly higher value than in the XX group (n = 9; p =.07). In women, relative PP change with ST in the RR group (n = 16) was higher than in the XX group (n = 17; p =.02).

Conclusions. The results indicate that the ACTN3 R577X polymorphism influences the response of quadriceps muscle power to ST in older adults.