The effects of body composition changes to observed improvements in cardiopulmonary parameters after exercise training with cardiac rehabilitation

STUDY OBJECTIVE: To discriminate the effects of body fat reduction on improvements in peak aerobic capacity made following exercise training during cardiac rehabilitation. DESIGN: Observational, prospective study. SETTING: Outpatient cardiovascular health center at regional academic center. PATIENT INTERVENTIONS: Peak oxygen uptake (pkVO2), percent body fat, lean body mass (LBM), and other anthropometric measures were assessed before and after a 3-month program of cardiac rehabilitation and exercise training in 500 consecutive cardiac patients following a major coronary event. Baseline pkVO2 was corrected for LBM (pk/VO2 lean) and compared with posttraining values. RESULTS: Following exercise training, percent body fat decreased 5% from 26.2+/-8.0 to 24.8+/-7.5 (p<0.0001), and LBM increased 1% from 61.3+/-12.5 to 61.7+/-11.8 kg (p=0.02). pk/VO2 increased 16% from 16.0+/-4.1 to 18.5+/-4.8 mL/kg/min (p<0.0001), and pkVO2 lean increased 13% from 21.7+/-5.3 to 24.6+/-6.0 mL/kg/min (p<0.0001). Isolating the effects of reduction in body fat, we discern that these changes contributed to 0.3 of the 2.5 mL/kg/min increase in pkVO2 or 12% of the increase in pkVO2 observed. CONCLUSIONS: Changes in body composition, as a consequence of dietary and exercise modification, contribute to 12% of the "observed" improvement noted in weight-adjusted peak aerobic capacity following cardiac rehabilitation and exercise training. Changes in pkVO2 lean should be used by investigators to assess the singular effects of exercise conditioning alone.