title: Alpha-actinin-3 (ACTN3) R577X polymorphism influences knee extensor peak power response to strength training in older men and women.
abstract: 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 approximately 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.
authors.affiliation: Department of Kinesiology, University of Maryland, College Park, MD 20742, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Delmonico
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Kostek
authors.forename: Neil A
authors.initials: NA
authors.lastname: Doldo
authors.forename: Brian D
authors.initials: BD
authors.lastname: Hand
authors.forename: Sean
authors.initials: S
authors.lastname: Walsh
authors.forename: Joan M
authors.initials: JM
authors.lastname: Conway
authors.forename: Craig R
authors.initials: CR
authors.lastname: Carignan
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Roth
authors.forename: Ben F
authors.initials: BF
authors.lastname: Hurley
mesh_terms: D000185:Actinin / Q000235:genetics*; D000368:Aged; D000369:Aged, 80 and over; D001120:Arginine; D003430:Cross-Sectional Studies; D015444:Exercise; D005260:Female; D006801:Humans; D007717:Knee; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000235:genetics*; D053580:Muscle Strength / Q000235:genetics*; D010807:Physical Endurance; D005082:Physical Exertion; D010809:Physical Fitness; D011110:Polymorphism, Genetic; D012727:Sex Characteristics
chemical_list: C118456:ACTN3 protein, human; D000185:Actinin; D001120:Arginine