Effect of single-set resistance training on quality of life in COPD patients enrolled in pulmonary rehabilitation.

BACKGROUND Single-set resistance training (SSRT) improves strength and function in older adults with COPD. However, its effect on quality of life (QOL) has not been evaluated. This study evaluated the effect of SSRT on QOL in COPD patients enrolled in pulmonary rehabilitation (PR) and identified relationships between muscular strength, endurance and QOL. METHODS Nineteen men and women (70.5 ± 5.0 years old) with COPD completed 8 weeks of PR alone or PR plus SSRT. QOL was measured using the Medical Outcomes Study Short Form 36. Upper and lower body strength was measured using chest and leg press, and lower body endurance was measured with the 6-min walk test. RESULTS There were no significant differences in QOL between PR with versus without SSRT before or after PR. Both groups demonstrated significant improvements in QOL, including the Physical Function (P = .02), Role Physical (P = .002), Vitality (P = .03), Social Functioning (P = .03), and Mental Health (P = .04) domains. Before PR, only lower body strength and endurance were significantly related to Physical Function (r = 0.53, P = .02 and r = 0.51, P = .03, respectively). After the exercise program, upper body strength as well as lower body strength and endurance were significantly related to Physical Function (r = 0.57, P = .01, r = 0.51, P = .03, and r = 0.62, P = .005, respectively), although improvements in Physical Function were predicted solely by improvements in upper body strength (r = 0.54, P = .02). CONCLUSIONS The addition of SSRT to traditional PR does not affect overall improvements in QOL that are influenced primarily by an increase in upper body strength. Our findings suggest a threshold effect for exercise training, such that, once a threshold stimulus has been achieved, further improvements in QOL are not dose-dependent.