title: ACTN3 X-allele carriers had greater levels of muscle damage during a half-ironman.
abstract: OBJECTIVE
  Alpha-actinin-3, encoded by the ACTN3 gene, is an actin-binding protein with an important role in myofibril contraction and muscle force output. In humans, there is a relatively common deficiency of the α-actinin-3 due to homozygosity in a polymorphism of the ACTN3 gene (R577X, rs1815739), that has been related to decreased resistance to strain during voluntary muscle contractions. The purpose of this study was to investigate the influence of the ACTN3 genotype on the level of exercise-induced muscle damage attained by 23 experienced triathletes during an official half-ironman competition.
  
  
  METHODS
  Before and after the race, a sample of venous blood was obtained and jump height was measured during a countermovement jump. The changes in serum creatine kinase (CK-MM isoform) were measured in the blood samples and muscle pain was measured with a visual analogue scale (0-10 cm). Data from RX heterozygotes and XX mutant homozygotes were grouped as X-allele carriers (n = 13) and compared to RR homozygotes (n = 10).
  
  
  RESULTS
  Race time was very similar between groups (313 ± 31 vs. 313 ± 25 min; P = 0.45); however, pre-to-post-competition reduction in jump height was greater in X-allele carriers than RR homozygotes (-18.4 ± 11.4 vs. -8.2 ± 6.9%; P = 0.04). At the end of the race, X-allele carriers presented higher serum CK-MM concentrations (682 ± 144 vs. 472 ± 269 U/L; P = 0.03), and there was also a tendency for higher self-reported values of lower limb muscle pain (7.7 ± 1.1 vs. 6.3 ± 2.3 cm; P = 0.06).
  
  
  CONCLUSIONS
  X-allele triathletes in the ACTN3 R577X polymorphism presented greater signs of exercise-induced muscle damage during a half-ironman race than RR homozygotes.
authors.affiliation: Exercise Physiology Laboratory, Camilo José Cela University, C/Castillo de Alarcon, 49, Villafranca del Castillo, 28692, Madrid, Spain. jdelcoso@ucjc.edu.
authors.forename: Juan
authors.identifier: http://orcid.org/0000-0002-5785-984X
authors.initials: J
authors.lastname: Del Coso
authors.affiliation: Exercise Physiology Laboratory, Camilo José Cela University, C/Castillo de Alarcon, 49, Villafranca del Castillo, 28692, Madrid, Spain.
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Salinero
authors.affiliation: Exercise Physiology Laboratory, Camilo José Cela University, C/Castillo de Alarcon, 49, Villafranca del Castillo, 28692, Madrid, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Lara
authors.affiliation: Exercise Physiology Laboratory, Camilo José Cela University, C/Castillo de Alarcon, 49, Villafranca del Castillo, 28692, Madrid, Spain.
authors.forename: César
authors.initials: C
authors.lastname: Gallo-Salazar
authors.affiliation: Exercise Physiology Laboratory, Camilo José Cela University, C/Castillo de Alarcon, 49, Villafranca del Castillo, 28692, Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Areces
authors.affiliation: Exercise Physiology Laboratory, Camilo José Cela University, C/Castillo de Alarcon, 49, Villafranca del Castillo, 28692, Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Puente
authors.affiliation: Exercise Physiology Laboratory, Camilo José Cela University, C/Castillo de Alarcon, 49, Villafranca del Castillo, 28692, Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Herrero
mesh_terms: D000185:Actinin / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000483:Alleles; D016022:Case-Control Studies; D015444:Exercise; D005260:Female; D006579:Heterozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide
chemical_list: C118456:ACTN3 protein, human; D000185:Actinin
keywords: Endurance performance; Muscle fatigue; Rhabdomyolysis; Single nucleotide polymorphism; Triathlon