The effects of inspiratory muscle training on exercise performance in chronic airflow limitation.

Using a simple, inexpensive, at-home program, 12 patients with moderate-to-severe chronic air flow limitation trained their inspiratory muscles. All showed increased inspiratory muscle endurance with no change in inspiratory muscle strength. Seven of the twelve patients increased their endurance time for submaximal exercise beyond the 90% confidence limits determined by 2 pretraining tests (i.e., a more than 40% increase in endurance time). The same group of 7 patients increased the maximal power output (p less than 0.005) and peak oxygen uptake (p less than 0.05) on a progressive exercise test after 2 months of training and increased the distance walked in 12 min after both 1 (p less than 0.005) and 2 (p less than 0.005) months of training. In 6 of the 7 patients in this group, the pretraining submaximal exercise tests were accompanied by electromyographic changes heralding inspiratory muscle fatigue. Their increased endurance time post-training was associated with a delay or absence of these changes. In the other group of 5 patients, who showed no change in exercise performance with training, electromyographic changes heralding inspiratory muscle fatigue were never observed in submaximal exercise tests. We concluded that although the endurance of the inspiratory muscles of patients with chronic airflow limitation is increased, specific training of the inspiratory muscles is usually associated with improved exercise performance only in those who demonstrate electromyographic changes heralding inspiratory muscle fatigue during exercise.