Effects of Resistance-Based Respiratory Muscle Training on Inspiratory Muscle Function and Exercise Performance in Young Adults

During heavy and severe-intensity exercise, the work of breathing (Wb) increases, leading to higher metabolic demands on the respiratory muscles. Previous research has shown that this increased Wb can reduce blood flow to the locomotor muscles in the legs, likely due to a “stealing” effect by the diaphragm. This phenomenon is particularly evident in diseases associated with increased Wb, such as chronic obstructive pulmonary disease (COPD) and heart failure. Respiratory muscle training (RMT) may improve the vascular and metabolic control of the diaphragm during exercise, reducing the local metabolic perturbation in this muscle and restoring blood flow distribution to the locomotory muscles. We tested the hypothesis that resistance-based RMT would increase diaphragm thickness, inspiratory muscle strength, and maximal cycling power during a VO 2 peak test. Four young adults (age: 21 ± 0.3 years; female: n = 3, male: n = 1) participated in the study. Measurements of diaphragm thickness (via ultrasound), inspiratory muscle strength (maximal inspiratory pressure, MIP), and cardiopulmonary exercise fitness (cycling VO 2 peak) were taken before and after 5-6 weeks of resistance RMT (5-6 days/week). Following RMT, MIP significantly increased compared to pre-training values (Pre-RMT: 106.88 ± 29 cmH 2 O; Post-RMT: 158.48 ± 24 cmH 2 O). Although diaphragm thickness showed a numerical increase, the change was not statistically significant (Pre-RMT: 2.47 ± 0.18 mm; Post-RMT: 2.81 ± 0.13 mm, P = 0.13). RMT significantly improved VO 2 peak power output (Pre-RMT: 170.11 ± 32.19 watts; Post-RMT: 194.26 ± 24.11 watts, P = 0.04), but there was no significant change in VO 2 peak itself (Pre-RMT: 35.50 ± 2.58 ml/kg/min; Post-RMT: 34.41 ± 2.92 ml/kg/min, P = 0.28). Despite a small sample size for this pilot project (n=4), these findings suggest that five to six weeks of resistance-based RMT significantly improve inspiratory muscle strength and cycling power during VO 2 peak testing, potentially enhancing tolerance to severe-intensity exercise. While the mechanistic basis of these effects remains to be explored, these results may be relevant for individuals with elevated Wb and reduced exercise capacity, as well as those traveling to high altitudes for work or recreation, where Wb is also increased. NIH 2L30HL134123-03 (Ferguson) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.