Comparative effects of inspiratory and expiratory muscle training on diaphragm adaptations and respiratory function in adolescent athletes: a randomized-controlled study.

In 30 seconds

This randomized controlled study compared inspiratory muscle training (IMT) with expiratory muscle training (EMST) in 26 adolescent female volleyball players. Both groups trained for 4 weeks alongside regular sports training. Diaphragm thickness during inspiration and expiration, maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) showed significant time effects (all p < 0.001), but there were no significant group-by-time interactions. Thus, the measured improvements were not shown to differ between IMT and EMST. Diaphragm stiffness and respiratory muscle endurance did not change significantly.

Key findings

• Diaphragm thickness during inspiration and expiration and MIP and MEP showed significant time effects (all p < 0.001).
• No significant group × time interactions were detected for diaphragm thickness, respiratory pressures, or pulmonary function parameters (p > 0.05).
• PEF% showed a significant time effect (p = 0.022), without a significant group × time interaction.
• Diaphragm stiffness and respiratory muscle endurance (Tmax) did not change significantly over time.

Why it matters

The findings suggest that respiratory muscle training alongside sports training may coincide with changes in diaphragm thickness and respiratory muscle strength in adolescent female volleyball players. The absence of detected differences between IMT and EMST means this study does not establish that one approach produces greater adaptations. The results also distinguish these changes from diaphragm stiffness and endurance, which did not significantly change.

What to keep in mind

The study included 26 adolescent female volleyball players and assessed outcomes only before and after a 4-week intervention; the abstract reports no longer-term follow-up.