Purpose: Previous studies have linked an insertion/deletion polymorphism in the angiotensin-converting enzyme (ACE) gene with variability in muscle strength responses to strength training (ST), though conclusions have been inconsistent across investigations. Moreover, most previous studies have not investigated the influence of sex on the association of ACE I/D genotype with muscle phenotypes. The purpose of this study was to investigate the association of ACE genotype with muscle phenotypes before and after ST in older men and women. Methods: Eighty-six inactive men and 139 inactive women, ages 50-85 yr (mean: 62 yr), were studied before and after 10 wk of unilateral knee extensor ST. The one-repetition maximum (1RM) test was used to assess knee extensor muscle strength, and computed tomography was used to measure quadriceps muscle volume (MV). Differences were compared among ACE genotype groups (II vs ID vs DD). Results: Across the entire cohort at baseline, ACE genotype was significantly associated with total lean mass and body weight, with higher values in DD genotype carriers (both P < 0.05). At baseline, DD genotype carriers exhibited significantly greater MV compared with II genotype carriers for both the trained leg (men: 1828 +/- 44 vs 1629 +/- 70; women: 1299 +/- 34 vs 1233 +/- 49; P = 0.02) and untrained leg (men: 1801 +/- 46 vs 1559 +/- 72; women: 1268 +/- 36 vs 1189 +/- 51; P = 0.01), with no significant genotype x sex interaction. No ACE genotype associations were observed for the 1RM or MV adaptations to ST in either men or women. Conclusions: In the present study, ACE genotype was associated with baseline differences in muscle volume, but it was not associated with the muscle hypertrophic response to ST.
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