Strength training : importance of genetic factors

• Published in: Medicine and science in sports and exercise 1998-05, Vol.30 (5), p.724-731
• Main Authors: THOMIS, M. A. I, BEUNEN, G. P, MAES, H. H, BLIMKIE, C. J, VAN LEEMPUTTE, M, CLAESSENS, A. L, MARCHAL, G, WILLEMS, E, VLIETINCK, R. F
• Format: Article
• Language: English
• Subjects: Adult; Arm; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Genetic Variation; Genetics of eukaryotes. Biological and molecular evolution; Genotype; Human; Humans; Male; Physical Endurance - genetics; Physical Fitness; Population genetics, reproduction patterns; Space life sciences; Twins, Dizygotic; Twins, Monozygotic; Weight Lifting
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1097/00005768-199805000-00013

This study focuses on the quantification of genetic and environmental factors in arm strength after high-resistance strength training. 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 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%). 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.