title: Elimination of influences of the ACTN3 R577X variant on oxygen uptake by endurance training in healthy individuals.
abstract: OBJECTIVE
  To study the relationship between the ACTN3 R577X polymorphism and oxygen uptake (VO2) before and after exercise training.
  
  
  METHODS
  Police recruits (N=206, 25±4 y) with RR (n=75), RX (n=97), and XX (n=33) genotypes were selected. After baseline measures, they underwent 18 wk of running endurance training. Peak VO2 was obtained by cardiopulmonary exercise testing.
  
  
  RESULTS
  Baseline body weight was not different among genotypes. At baseline, XX individuals displayed higher VO2 at anaerobic threshold, respiratory compensation point, and exercise peak than did RR individuals (P<.003). Endurance training significantly increased VO2 at anaerobic threshold, respiratory compensation point, and exercise peak (P<2×10(-6)), but the differences between XX and RR were no longer observed. Only relative peak VO2 exercise remained higher in XX than in RR genotype (P=.04). In contrast, the increase in relative peak VO2 was greater in RR than in XX individuals (12% vs 6%; P=.02).
  
  
  CONCLUSIONS
  ACTN3 R577X polymorphism is associated with VO2. XX individuals have greater aerobic capacity. Endurance training eliminates differences in peak VO2 between XX and RR individuals. These findings suggest a ceiling-effect phenomenon, and, perhaps, trained individuals may not constitute an adequate population to explain associations between phenotypic variability and gene variations.
authors.affiliation: Laboratory of Genetics and Molecular Cardiology, University of São Paulo Medical School, São Paulo, Brazil.
authors.forename: Michelle S M
authors.initials: MS
authors.lastname: Silva
authors.forename: Wladimir
authors.initials: W
authors.lastname: Bolani
authors.forename: Cleber R
authors.initials: CR
authors.lastname: Alves
authors.forename: Diogo G
authors.initials: DG
authors.lastname: Biagi
authors.forename: José R
authors.initials: JR
authors.lastname: Lemos
authors.forename: Jeferson L
authors.initials: JL
authors.lastname: da Silva
authors.forename: Patrícia A
authors.initials: PA
authors.lastname: de Oliveira
authors.forename: Guilherme B
authors.initials: GB
authors.lastname: Alves
authors.forename: Edilamar M
authors.initials: EM
authors.lastname: de Oliveira
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Negrão
authors.forename: José E
authors.initials: JE
authors.lastname: Krieger
authors.forename: Rodrigo G
authors.initials: RG
authors.lastname: Dias
authors.forename: Alexandre C
authors.initials: AC
authors.lastname: Pereira
mesh_terms: D000185:Actinin / Q000235:genetics*; D000328:Adult; D015444:Exercise / Q000502:physiology*; D014644:Genetic Variation; D005838:Genotype; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D010641:Phenotype; D010807:Physical Endurance / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide; D055815:Young Adult
chemical_list: C118456:ACTN3 protein, human; D000185:Actinin