Effects of high-intensity inspiratory muscle warm-up on inspiratory muscle strength and accessory inspiratory muscle activity.

This study aimed to determine the effects of work-matched moderate-intensity and high-intensity inspiratory muscle warm-up (IMW) on inspiratory muscle strength and accessory inspiratory muscle activity. Eleven healthy men performed three IMWs at different intensities, namely, placebo, moderate-intensity, and high-intensity, set, respectively, at 15 %, 40 %, and 80 % of maximal inspiratory mouth pressure (MIP). MIP was measured before and after IMW. Electromyography (EMG) was recorded for the sternocleidomastoid muscle (SCM) and intercostal muscles (IC) during IMW. MIP increased significantly in the moderate-intensity condition (104.2 ± 5.1 %, p < 0.05) and high-intensity condition (106.5 ± 6.2 %, p < 0.01) after IMW. The EMG amplitudes of the SCM and IC during IMW were significantly higher in the order of high-intensity, moderate-intensity, and placebo conditions. There was a significant correlation between changes in MIP and EMG amplitude of the SCM (r = 0.60, p < 0.01) and IC (r = 0.47, p < 0.01) during IMW. These findings suggest that high-intensity IMW increases neuromuscular activity in the accessory inspiratory muscles, which may improve inspiratory muscle strength.