ACE ID genotype and the muscle strength and size response to unilateral resistance training

Purpose: To examine associations among the angiotensin I-converting enzyme (ACE) insertion (I)/deletion (D) polymorphism and the response to a 12-wk (2 d·wk^-1) unilateral, upper-arm resistance training (RT) program in the trained (T, nondominant) and untrained (UT, dominant) arms. Methods: Subjects were 631 (mean ± SEM, 24.2 ± 0.2 yr) white (80%) men (42%) and women (58%). The ACE ID genotype was in Hardy-Weinberg equilibrium with frequencies of 23.1, 46.1, and 30.8% for ACE II, ID, and DD, respectively (x² = 1.688, P = 0.430). Maximum voluntary contraction (MVC) and one-repetition maximum (1RM) assessed peak elbow flexor muscle strength. Magnetic resonance imaging measured biceps muscle cross-sectional area (CSA). Multiple variable and repeated-measures ANCOVA tested whether muscle strength and size differed at baseline and pre- to post-RT among T and UT and ACE ID genotype. Results: Baseline muscle strength and size were greater in UT than T (P < 0.001) and did not differ among ACE ID genotype in either arm (P ≥ 0.05). In T, MVC increases were greater for ACE II/ID (22%) than DD (17%) (P < 0.05), whereas IRM (51%) and CSA (19%) gains were not different among ACE ID genotype pre- to post-RT (P ≥ 0.05). In UT, MVC increased among ACE II/ID (7%) (P < 0.001) but was similar among ACE DD (2%) pre- to post-RT (P ≥ 0.05). In UT, IRM (11%) and CSA (2%) increases were greater for ACE DD/ID than ACE II (1RM, 7%; CSA, -0.1%) (P < 0.05). ACE ID genotype explained approximately 1% of the MVC response to RT in T and approximately 2% of MVC, 2% of IRM, and 4% of CSA response in UT (P < 0.05). Conclusion: ACE ID genotype is associated with the contralateral effects of unilateral RT, perhaps more so than with the muscle strength and size adaptations that result from RT.