Inspiratory muscle training effects on cycling during acute hypoxic exposure

Introduction: Hypoxic environments increase the physiological demands of exercise. Inspiratory muscle training can reduce the demands of exhaustive exercise in this environment. This study examined the impact of inspiratory muscle training on moderate intensity hypoxic cycling exercise.

Methods: Seventeen healthy adult men undertook four weeks of inspiratory muscle training (n = 8) or four weeks of sham inspiratory muscle training (n = 9). Subjects completed four fixed- intensity (100 watts) and duration (10 minutes) cycle ergometry tests. Two were undertaken breathing normoxic ambient air, and two breathing a hypoxic gas mixture (14.6% oxygen, balance nitrogen). One normoxic and hypoxic test occurred before, and one after, inspiratory muscle training.

Results: Inspiratory muscle training increased maximal inspiratory mouth pressure by 21 ± 16 cmH2O. Arterial oxygen saturation and its ratio to minute ventilation also increased after inspiratory muscle training during hypoxic exercise from 83 ± 4% to 86 ± 3% (approximately 3%) and 2.95 ± 0.48 to 3.52 ± 0.54 %.l.min-1(approximately 21%), respectively. In addition, minute ventilation, and carbon dioxide output fell by 12-13% after inspiratory muscle training during hypoxic exercise.

Discussion: Inspiratory muscle training reduced the physiological demand of moderate intensity exercise during acute hypoxic, but not normoxic, exercise. It may therefore be of benefit in adults exercising in a hypoxic environment.