Effects of simultaneous aerobic and inspiratory muscle training on diaphragm function, respiratory muscle strength, endurance, and fatigue index: randomized-controlled trial.

Abstract

Purpose: This study aims to investigate the effects of Walking-Specific Inspiratory Muscle Training (W-SIMT) on diaphragm thickness-stiffness, pulmonary and respiratory muscle functions, and fatigue index.

Research question: Do individuals who performed W-SIMT have better diaphragm functions, respiratory muscle strength, endurance, and performance?

Methods: Twenty-seven healthy participants were included in the randomized-controlled study. The simultaneous inspiratory and aerobic exercise training (60-80% of maximal heart rate; 3 days/weeks; 4 weeks) was performed in the W-SIMT group (n = 14). The same aerobic (walking) exercise training protocol (n = 13) without Inspiratory Muscle Training (IMT) was applied in the walking (aerobic) group. The W-SIMT group performed 30 consecutive inspirations with 2-min rest (2 sets) in 50% of Maximal Inspiratory Pressure (MIP) using an assistive inspiratory muscle training device simultaneously while walking. The diaphragm thickness and stiffness, pulmonary functions, MIP, Maximal Expiratory Pressure (MEP), sustained inspiratory maximal pressure (P_max), and fatigue index were evaluated before and 4 weeks after the intervention.

Results: There was a significant effect of group × time interaction for MIP (cmH₂O and %, respectively) (F = 28.719, p < 0.001; F = 10.640, p = 0.003), sum (Pmax) (F = 5.414, p = 0.029), and fatigue index (F = 4.775, p = 0.039), in favor of the W-SIMT group.

Conclusion: The distinctive combination of respiratory muscle training and aerobic exercise shows additional benefits enhancing particularly respiratory and anaerobic performance even over a short period. Further studies are needed to explore the long-term effects of W-SIMT.

Trial registry: Trial Registration Number: NCT06742372.