title: Strength training: importance of genetic factors.
abstract: OBJECTIVE
  This study focuses on the quantification of genetic and environmental factors in arm strength after high-resistance strength training.
  
  
  METHODS
  Male monozygotic (MZ, N = 25) and dizygotic (DZ, N = 16) twins (22.4 +/- 3.7 yr) participated in a 10-wk resistance training program for the elbow flexors. The evidence for genotype*training interaction, or association of interindividual differences in training effects with the genotype, was tested by a two-way ANOVA in the MZ twins and using a bivariate model-fitting approach on pre- and post-training phenotypes in MZ and DZ twins. One repetition maximum (1RM), isometric strength, and concentric and eccentric moments in 110 degree arm flexion at velocities of 30 degrees x s(-1), 60 degrees x s(-1), and 12 degrees x s(-1) were evaluated as well as arm muscle cross-sectional area (MCSA).
  
  
  RESULTS
  Results indicated significant positive training effects for all measures except for maximal eccentric moments. Evidence for genotype*training interaction was found for 1RM and isometric strength, with MZ intra-pair correlations of 0.46 and 0.30, respectively. Bivariate model-fitting indicated that about 20% of the variation in post-training 1RM, isometric strength, and concentric moment at 120 degrees x s(-1) was explained by training-specific genetic factors that were independent from genetic factors that explained variation in the pretraining phenotype (30-77%).
  
  
  CONCLUSIONS
  Genetic correlations between measures of pre- and post-training strength were indicative for high pleiotropic gene action and minor activation of training-specific genes during training.
authors.affiliation: Dept. of Kinesiology, Faculty of Physical Education and Physiotherapy, Katholieke Univeriteit Leuven, Belgium. martine.thomis@flok.kuleuven.ac.be
authors.forename: M A
authors.initials: MA
authors.lastname: Thomis
authors.forename: G P
authors.initials: GP
authors.lastname: Beunen
authors.forename: H H
authors.initials: HH
authors.lastname: Maes
authors.forename: C J
authors.initials: CJ
authors.lastname: Blimkie
authors.forename: M
authors.initials: M
authors.lastname: Van Leemputte
authors.forename: A L
authors.initials: AL
authors.lastname: Claessens
authors.forename: G
authors.initials: G
authors.lastname: Marchal
authors.forename: E
authors.initials: E
authors.lastname: Willems
authors.forename: R F
authors.initials: RF
authors.lastname: Vlietinck
mesh_terms: D000328:Adult; D001132:Arm; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000235:genetics*; D010809:Physical Fitness; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D014891:Weight Lifting