title: Covariance of isometric and dynamic arm contractions: multivariate genetic analysis.
abstract: The purpose of the present study was to examine genetic and environmental contributions to individual differences in maximal isometric, concentric and eccentric muscle strength and muscle cross-sectional area (MCSA) of the elbow flexors. A generality versus specificity hypothesis was explored to test whether the 4 strength variables share a genetic component or common factors in the environment or whether the genetic/environmental factors are specific for each strength variable. The 4 variables under study were measured in 25 monozygotic and 16 dizygotic male Caucasian twin pairs (22.4 +/- 3.7 years). The multivariate genetic analyses showed that all 4 variables shared a genetic and environmental component, which accounted for 43% and 6% in MCSA (h2 = 81%), 47% and 20% in eccentric (h2 = 65%), 58% and 4% in isometric (h2 = 70%) and 32% and 1% in concentric strength (h2 = 32%) respectively. The remaining variation was accounted for by contraction type specific and muscle cross-sectional area specific genetic and environmental effects, which accounted for 38% and 14% in MCSA, 18% and 15% in eccentric, 12% and 26% in isometric and 0% and 67% in concentric strength respectively. This exploratory multivariate study suggests shared pleiotropic gene action for MCSA, eccentric, isometric and concentric strength, with a moderate to high genetic contribution to the variability of these characteristics.
authors.affiliation: Department of Biomedical Kinesiology, Research Center for Exercise and Health, Faculty of Kinesiology and Rehabilitation Sciences, Katholieke Universiteit Leuven, Leuven, Belgium. gunther.demars@faber.kuleuven.be
authors.forename: Gunther
authors.initials: G
authors.lastname: De Mars
authors.forename: Martine A I
authors.initials: MA
authors.lastname: Thomis
authors.forename: An
authors.initials: A
authors.lastname: Windelinckx
authors.forename: Marc
authors.initials: M
authors.lastname: Van Leemputte
authors.forename: Hermine H
authors.initials: HH
authors.lastname: Maes
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Blimkie
authors.forename: Albrecht L
authors.initials: AL
authors.lastname: Claessens
authors.forename: Robert
authors.initials: R
authors.lastname: Vlietinck
authors.forename: Gaston
authors.initials: G
authors.lastname: Beunen
mesh_terms: D000293:Adolescent; D000328:Adult; D001132:Arm; D004550:Elbow; D006801:Humans; D007537:Isometric Contraction / Q000235:genetics*; D008297:Male; D015999:Multivariate Analysis; D053580:Muscle Strength / Q000235:genetics*; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*