ABSTRACT

　Previous studies have reported that respiratory muscle training improves performance during prolonged high-intensity exercise; however, the mechanism remains unclear. With an aim to gain insights into the underlying mechanism, we simultaneously monitored respiratory and lower limb muscle oxygenation patterns using near-infrared spectroscopy (NIRS) during high-intensity cycling exercise before and after 6 weeks of inspiratory muscle training. Sixteen healthy young men were assigned to either experimental (inspiratory muscle training : IMT) or sham (SHAM) training groups and underwent inspiratory muscle training for more than 5 days per week for 6 weeks. The subjects underwent constant load test at 90% VO₂max on a cycle ergometer until exhaustion both before and after training. Oxygenation in both intercostal and vastus lateralis muscles were measured using NIRS during the test. In addition, maximal inspiratory pressure (MIP) was measured using spirometer every 2 weeks for the duration of the training. After inspiratory muscle training, MIP increased significantly in the IMT group but not in the SHAM group. Furthermore, time to the limit of exercise tolerance prolonged significantly in the IMT group but not in the SHAM group. However, no significant changes were found in oxygenation in both intercostal and vastus lateralis muscles in both the groups. These findings suggest that inspiratory muscle training improves high-intensity cycling exercise performance by factors other than enhanced oxygenation in both respiratory and lower limb muscles.

DESCENTE SPORTS SCIENCE Vol.37/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE