The effect of inspiratory muscle training (IMT) on exercise capacity in patients with chronic airflow limitation (CAL) has been debated. The present study was planned to further investigate the effects of IMT on exercise performance. Twenty patients (aged 62 +/- 1 yrs; forced expiratory volume in one second/forced vital capacity (FEV1/FVC) 36 +/- 2%) were trained 30 min daily for 6 days a week during 10 weeks, with either 30% (group 1) or 10% (group 2) of peak maximal inspiratory pressure (PImax) as a training load. Exercise performance was evaluated by the distance walked in 6 min (6MWD) and by changes in oxygen consumption (VO2) and minute ventilation (VE) during a progressive exercise test. Changes in PImax and dyspnoea were also measured. Results showed a significant increment in peak PImax in both groups, whereas dyspnoea and 6MWD improved only in group 1 (p < 0.05 and p < 0.01, respectively). No increment in maximal workload or in peak VO2 was observed in either group. Patients in group 1, however, showed a reduction in VE and VO2 for the same exercise. A correlation between changes in VE and VO2 during a workload of 75 kpm/min was observed in group 1 (r = 0.92; p < 0.001). We conclude that inspiratory muscle training using a load of 30% peak maximal inspiratory pressure, improves dyspnoea, increases walking capacity and reduces the metabolic cost of exercise.
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