The Effect of Preexercise Expiratory Muscle Loading on Exercise Tolerance in Healthy Men

Abstract

Purpose 

Acute nonfatiguing inspiratory muscle loading transiently increases diaphragm excitability and global inspiratory muscle strength and may improve subsequent exercise performance. We investigated the effect of acute expiratory muscle loading on expiratory muscle function and exercise tolerance in healthy men.

Methods 

Ten males cycled at 90% of peak power output to the limit of tolerance (T_LIM) after 1) 2 × 30 expiratory efforts against a pressure-threshold load of 40% maximal expiratory gastric pressure (Pga_MAX) (EML-EX) and 2) 2 × 30 expiratory efforts against a pressure-threshold load of 10% Pga_MAX (SHAM-EX). Changes in expiratory muscle function were assessed by measuring the mouth pressure (PE_MAX) and Pga_MAX responses to maximal expulsive efforts and magnetically evoked (1 Hz) gastric twitch pressure (Pga_tw).

Results 

Expiratory loading at 40% of Pga_MAX increased PE_MAX (10% ± 5%, P = 0.001) and Pga_MAX (9% ± 5%, P = 0.004). Conversely, there was no change in PE_MAX (166 ± 40 vs 165 ± 35 cm H₂O, P = 1.000) or Pga_MAX (196 ± 38 vs 192 ± 39 cm H₂O, P = 0.215) from before to after expiratory loading at 10% of Pga_MAX. Exercise time was not different in EML-EX versus SHAM-EX (7.91 ± 1.96 vs 8.09 ± 1.77 min, 95% CI = −1.02 to 0.67, P = 0.651). Similarly, exercise-induced expiratory muscle fatigue was not different in EML-EX versus SHAM-EX (−28% ± 12% vs −26% ± 7% reduction in Pga_tw amplitude, P = 0.280). Perceptual ratings of dyspnea and leg discomfort were not different during EML-EX versus SHAM-EX.

Conclusion 

Acute expiratory muscle loading enhances expiratory muscle function but does not improve subsequent severe-intensity exercise tolerance in healthy men.