Training Specificity of Inspiratory Muscle Training Methods: A Randomized Trial

Area of Science:

• Respiratory Physiology
• Exercise Science

Background:

• Inspiratory muscle training (IMT) is crucial for respiratory health.
• Standard IMT protocols often use pressure threshold loading initiated from residual volume (RV).

Purpose of the Study:

• To compare the effects of three IMT protocols on maximal inspiratory pressures (PImax) and flow (V̇Imax) at various lung volumes.
• To determine if IMT initiated from functional residual capacity (FRC) or using tapered flow resistive loading improves inspiratory muscle function more broadly than standard RV-initiated pressure threshold loading.

Main Methods:

• 48 healthy volunteers underwent 4 weeks of daily IMT (30 breaths/session).
• Protocols included: 1) pressure threshold loading from RV, 2) pressure threshold loading from FRC, 3) tapered flow resistive loading from RV.
• PImax and V̇Imax were measured at RV, FRC, and midway between FRC and total lung capacity (1/2 IC) before and after training.

Main Results:

• PImax improved at all lung volumes with FRC-initiated pressure threshold loading and tapered flow resistive loading.
• Standard RV-initiated pressure threshold loading only improved PImax at RV and FRC.
• V̇Imax significantly increased at all lung volumes with tapered flow resistive loading, and at higher lung volumes (FRC, 1/2 IC) with FRC-initiated pressure threshold loading.

Conclusions:

• IMT using tapered flow resistive loading or pressure threshold loading from FRC offers superior improvements in respiratory muscle function at higher lung volumes.
• Standard IMT protocols are limited to improvements at lower lung volumes.
• Further studies in larger populations are recommended to validate these findings.