Strength training: importance of genetic factors.
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.
Thomis
M A
MA
Dept. of Kinesiology, Faculty of Physical Education and Physiotherapy, Katholieke Univeriteit Leuven, Belgium. martine.thomis@flok.kuleuven.ac.be
Beunen
G P
GP
Maes
H H
HH
Blimkie
C J
CJ
Van Leemputte
M
M
Claessens
A L
AL
Marchal
G
G
Willems
E
E
Vlietinck
R F
RF
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