The muscle strength and size response to upper arm, unilateral resistance training among adults who are overweight and obese.

Overweight and obesity result in musculoskeletal impairments that limit exercise capacity. We examined if the muscle strength and size response to resistance training (RT) differed among 687 young (mean +/- SEM, 24.2 +/- 0.2 years) overweight and obese (OW) compared to normal weight (NW) adults as denoted by the body mass index (BMI). Subjects were 449 NW (22.0 +/- 0.1 kg.m(-2), 23.4 +/- 0.3 years) and 238 OW (29.2 +/- 0.2 kg.m(-2), 25.6 +/- 0.4 years) men (n = 285) and women (n = 402) who underwent 12 weeks (2 d.wk(-1)) of RT of the nondominant arm. Maximum voluntary contraction (MVC) and 1 repetition maximum (1RM) assessed peak elbow flexor strength. Magnetic resonance imaging measured the biceps muscle cross sectional area (CSA). Multiple dependent variable analysis of covariance tested if muscle strength and size differed among BMI groups pre-, post-, and pre-to-post-RT. Overweight and obese had greater MVC, 1RM, and CSA than NW pre- and post-RT (p < 0.001). Maximum voluntary contraction and 1RM gains were not different between BMI groups pre- to post-RT (p >or= 0.05). When adjusted for baseline values, NW had greater relative MVC (21.2 +/- 1.0 vs. 17.4 +/- 1.4%) and 1RM (54.3 +/- 1.5 vs. 49.0 +/- 2.0%) increases than OW (p < 0.05). Normal weight also had greater allometric MVC (0.48 +/- 0.02 kg.kg(-0.67) vs. 0.40 +/- 0.03 kg.kg(-0.67)) and 1RM (0.25 +/- 0.00 vs. 0.22 +/- 0.01 kg.kg(-0.67)) gains than OW (p < 0.05). CSA gains were greater among OW than NW (3.6 +/- 0.2 vs. 3.2 +/- 0.1 cm(2)) (p < 0.001); however, relative CSA increases were not different between BMI groups (19.4 +/- 0.5 vs. 18.4 +/- 0.7%) (p >or= 0.05). Despite similar relative muscle size increases, relative and allometic strength gains were less among OW than NW. These findings indicate the short-term relative and allometric muscle strength response to RT may be attenuated among adults who are overweight and obese.