Genetic influences on the development of grip strength in adolescence
Article first published online: 12 FEB 2014
Copyright © 2014 Wiley Periodicals, Inc.
American Journal of Physical Anthropology
Volume 154, Issue 2, pages 189–200, June 2014
How to Cite
Isen, J., McGue, M. and Iacono, W. (2014), Genetic influences on the development of grip strength in adolescence. Am. J. Phys. Anthropol., 154: 189–200. doi: 10.1002/ajpa.22492
- Issue published online: 13 MAY 2014
- Article first published online: 12 FEB 2014
- Manuscript Revised: 29 JAN 2014
- Manuscript Accepted: 29 JAN 2014
- Manuscript Received: 21 SEP 2013
- National Institutes of Health. Grant Numbers: DA 013240, DA 05147, AA 09367
- physical strength;
- sexual dimorphism
Enhanced physical strength is a secondary sex characteristic in males. Sexual dimorphism in physical strength far exceeds sex differences in stature or total body mass, suggesting a legacy of intense sexual selection. Upper-body strength is a particularly promising marker of intrasexual competitiveness in young men. Consequently, it is assumed that sex-influenced gene expression contributes to the development of physical strength. It is unclear, however, whether the underlying sources of individual differences in strength development are comparable across sex. We obtained three measurements of hand-grip strength (HGS) over a six-year period spanning adolescence in male and female same-sex twins (N = 2,513). Biometrical latent growth models were used to partition the HGS variance at age 11 (intercept) and its growth over time (slope) into genetic and environmental components. Results demonstrated that variance around the intercept was highly heritable in both males and females (88% and 79%, respectively). In males, variance around the slope exceeded that of the intercept, while the reverse held for females. Additive genetic effects accounted for most (80%) of the variance around the slope in males, but were of less importance in females (heritability = 28%). Absolute genetic variance around the slope was nearly nine-fold higher in males. This striking disparity suggests that the developmental processes shaping HGS growth are different between the sexes. We propose that this might account for the sex-specific pattern of associations between HGS and external measures (e.g., digit ratio and physical aggression) typically reported in the literature. Our results underscore the role of endogenous androgenic influences in the development of physical strength. Am J Phys Anthropol 154:189–200, 2014. © 2014 Wiley Periodicals, Inc.