Chest. June 2004;125(6):2021-2028.
Background
Skeletal muscle wasting is related to muscle dysfunction, exercise intolerance, and increased mortality risk in patients with chronic obstructive pulmonary disease (COPD).
Study Objectives
The aims of this study were to investigate the effects of whole-body exercise training on body composition in normal-weight patients with COPD, and to study the relationship between changes in body composition and functional capacity.
Setting and Participants
Fifty patients with COPD (FEV1, 39% of predicted [SD, 16]) admitted to the pulmonary rehabilitation center at Hornerheide, and 36 healthy age-matched control subjects (for baseline comparison) were included.
Interventions
Patients participated in a standardized inpatient exercise training program consisting of daily submaximal cycle ergometry, treadmill walking, weight training, and gymnastics for 8 weeks.
Measurements
Fat-free mass (FFM) was measured by bioelectrical impedance analysis. None of the patients met the criteria for nutritional supplementation (body mass index <=21, or FFM index <=15 kg/m2 in women and <=16 kg/m2 in men). Exercise capacity was measured using incremental cycle ergometry. Isokinetic quadriceps strength was measured with a Biodex dynamometer (Biodex Medical Corporation; Shirley, NY).
Results
At baseline, patients were characterized by a significantly lower FFM than the control subjects. Age and FFM were independent predictors of skeletal muscle function and exercise capacity in patients. After rehabilitation, weight (72.4 +/- 9.8 to 73.0 +/- 9.4 kg, P < .05) significantly increased, as a result of increased FFM (52.4 +/- 7.3 to 53.4 +/- 7.7 kg, P < .05), while fat mass (20.0 +/- 6.1 to 19.6 +/- 5.7 kg) tended to decrease. Peak work rate (63 +/- 29 to 84 +/- 42 W, P < .001), maximal oxygen consumption (O2max) [1028 +/- 307 to 1229 +/- 421 mL/min, P < .001], and isokinetic quadriceps strength (82.5 +/- 36.4 to 90.3 +/- 34.9 Nm, P < .05) all improved. Changes in FFM were proportionally smaller than functional improvements, and were related to changes in O2max (r = 0.361, P < .05), but not to other changes in functional capacity.
Conclusions
Intensive exercise training per se is able to induce an anabolic response in normal-weight patients with COPD classified into Global Initiative for Chronic Obstructive Lung Disease stages III-IV. Improvements in exercise performance and muscle function are proportionally larger than increases in FFM.
Commentary
Approximately one third of patients with severe COPD experience skeletal muscle dysfunction that is often, at least in part, related to reduction in FFM. Skeletal muscle dysfunction associated with reduction in FFM is associated with reduced strength and exercise endurance and indeed also with increased utilization of health care resources and reduced survival. PR is known to improve the exercise tolerance of patients with severe COPD. In this study, the investigators have evaluated the effects of 8 weeks' comprehensive inpatient PR on exercise tolerance, body composition, and the relationship between changes in exercise tolerance to observed changes in FFM among patients with severe stable COPD and normal body weight. Multimodality exercise training lead to improvements in exercise capacity as well as increase in body weight, largely due to the increase in FFM. The change in FFM was related to improvements in maximal oxygen consumption. Changes in FFM were, however, of smaller magnitude than the magnitude of improvements in exercise tolerance. The authors concluded that exercise training can lead to an anabolic response with associated increase in FFM. However, additional mechanisms also likely play a role in the improvements in functional capacity noted following comprehensive PR.