Exercise breathing strategy following isocapnic voluntary hyperventilation to task failure

Healthy, trained individuals develop respiratory muscle fatigue (RMF), in part, due to the level of hyperpnea achieved during intensive exercise. When RMF is induced via a resistive loading task, subsequent exercise ventilation and related parameters are altered. In contrast, it is unclear how RMF induced via breathing at a volume load similar to that achieved during intense exercise affects subsequent exercise breathing dynamics and performance.;Purpose: To examine breathing pattern, operating lung volume (OLV), and whole body oxygen utilization (VO2) during submaximal cycling, as well as exercise performance, following induction of RMF via a high-volume challenge.;Methods: Twelve well-trained endurance athletes performed an incremental exercise test for the measurement of VO2max and returned on two additional occasions to perform cycling economy (CE) tests at workloads eliciting 55, 65, and 75% VO2max. The CE tests were performed with (FT) and without (CON) preliminarily completing an isocapnic voluntary hyperventilatory task to failure (IVH) in order to fatigue the respiratory muscles. Cycling time-to-exhaustion (Tlim) at 90% VO2max was used as an exercise performance measure. RMF was assessed using maximal volitional inspiratory (PImax) and expiratory (PEmax) mouth pressures. Statistical significance was set at p < 0.05.;Results: IVH (153.2 +/- 19.9 L*min-1 for 24.3 +/- 12.8 min) impaired respiratory muscle function compared to baseline (PImax, -141.2 +/- 6.3 vs. -128.6 +/- 5.7 cmH2O; PEmax, 197.2 +/- 8.9 vs. 183.1 +/-8.1 cmH2O). Minute ventilation (VE) was augmented at every workload during FT compared to CON. Breathing frequency and tidal volume were both altered, with subjects displaying a more rapid, shallow breathing pattern after IVH. The changes in VO2 and CE from CON to FT were correlated with the changes observed in VE at each workload. OLV remained largely unchanged. Tlim was 509 +/- 43 and 455 +/- 36 s (p = 0.06) during CON and FT, respectively.;Conclusion: Respiratory muscle fatigue resulting from a volume load similar to that during intensive exercise alters ventilation and breathing pattern during submaximal exercise. Those with the greatest change in ventilation show the largest impairment to exercise economy. Respiratory muscle fatigue via a high volume task may potentially limit exercise performance.