Effects of Age, Gender, and Myostatin Genotype on the Hypertrophic Response to Heavy Resistance Strength Training

University of Pittsburgh, Pittsburgh, Pennsylvania, United States
The Journals of Gerontology Series A Biological Sciences and Medical Sciences (Impact Factor: 5.42). 11/2000; 55(11):M641-8. DOI: 10.1093/gerona/55.11.M641
Source: PubMed


Because of the scarcity of data available from direct comparisons of age and gender groups using the same relative training stimulus, it is unknown whether older individuals can increase their muscle mass as much as young individuals and whether women can increase as much as men in response to strength training (ST). In addition, little is known about whether the hypertrophic response to ST is affected by myostatin genotype, a candidate gene for muscle hypertrophy.
Eleven young men (25 +/- 3 years, range 21-29 years), 11 young women (26 +/- 2 years, range 23-28 years), 12 older men (69 +/- 3 years, range 65-75 years), and 11 older women (68 +/- 2 years, range 65-73 years) had bilateral quadriceps muscle volume measurements performed using magnetic resonance imaging (MRI) before and after ST and detraining. Training consisted of knee extension exercises of the dominant leg three times per week for 9 weeks. The contralateral limb was left untrained throughout the ST program. Following the unilateral training period, the subjects underwent 31 weeks of detraining during which no regular exercise was performed. Myostatin genotype was determined in a subgroup of 32 subjects, of which five female subjects were carriers of a myostatin gene variant.
A significantly greater absolute increase in muscle volume was observed in men than in women (204 +/- 20 vs 101 +/- 13 cm3, p < .01), but there was no significant difference in muscle volume response to ST between young and older individuals. The gender effect remained after adjusting for baseline muscle volume. In addition, there was a significantly greater loss of absolute muscle volume after 31 weeks of detraining in men than in women (151 +/- 13 vs 88 +/- 7 cm3, p < .05), but no significant difference between young and older individuals. Myostatin genotype did not explain the hypertrophic response to ST when all 32 subjects were assessed. However, when only women were analyzed, those with the less common myostatin allele exhibited a 68% larger increase in muscle volume in response to ST (p = .056).
Aging does not affect the muscle mass response to either ST or detraining, whereas gender does, as men increased their muscle volume about twice as much in response to ST as did women and experienced larger losses in response to detraining than women. Young men were the only group that maintained muscle volume adaptation after 31 weeks of detraining. Although myostatin genotype may not explain the observed gender difference in the hypertrophic response to ST, a role for myostatin genotype may be indicated in this regard for women, but future studies are needed with larger subject numbers in each genotype group to confirm this observation.

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    • "These discrepancies are likely to arise from variances in training regimes, nutritional support and analytical techniques. Relative progression of training loads may be similar between younger and older individuals (Ivey et al. 2000, Mayhew et al. 2009) in part may be due to neural contributions (Hakkinen et al. 1998) as equal strength gains have been produced with limited gains in contractile mass in older age (Moritani &amp; deVries 1980, Mero et al. 2013). RE certainly improves muscle function in older age (Macaluso et al. 2004, Peterson et al. 2011), yet the gains in mass and strength appear to diminish compared with those of younger subjects. "
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    • "One possibility is a difference in neural recruitment patterns between men and women. This seems plausible given that relative strength increases are higher in women but relative hypertrophy may be higher in men (Hubal et al., 2005; Ivey et al., 2000; Peterson et al., 2011), suggesting that neural adaptations to RT are greater in women. Higher relative strength increases in women would result in higher relative specific training loads in women compared to men. "
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