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Evidence for an inadequate hyperventilation inducing arterial hypoxemia at submaximal exercise in all highly trained endurance athletes

DURAND, FABIENNE; MUCCI, PATRICK; PRÉFAUT, CHRISTIAN

Medicine & Science in Sports & Exercise: May 2000 - Volume 32 - Issue 5 - p 926-932
Basic Sciences: Original Investigations

DURAND, F., P. MUCCI, and C. PRÉFAUT. Evidence for an inadequate hyperventilation inducing arterial hypoxemia at submaximal exercise in all highly trained endurance athletes. Med. Sci. Sports Exerc., Vol. 32, No. 5, pp. 926–932, 2000.

Purpose The majority of highly trained endurance athletes with a maximal oxygen uptake greater than 60 mL·min−1·kg−1 develop exercise-induced hypoxemia (EIH). Yet some of them apparently do not. The pathophysiology of EIH seems to be multifactorial, and one explanatory hypothesis is a relative hypoventilation. Nevertheless, conflicting results have been reported concerning its contribution to EIH. The aim of this study was to compare the cardiorespiratory responses to maximal exercise of highly trained endurance athletes demonstrating the same aerobic capacity without EIH (N athletes) and with EIH (H athletes).

Methods Ten N athletes and twelve H athletes performed an incremental exercise test. Measurements of arterial blood gases and cardiorespiratory parameters were performed at rest and during exercise.

Results All athletes presented a significant decrease in PaO2 (P < 0.05) from rest up to 80% O2max associated with an increase in PaCO2, both findings consistent with a relative hypoventilation. Then the H athletes, who had a greater training volume per week and a higher second ventilatory threshold than the N athletes (respectively, 17 ± 1.1 vs 13.1 ± 0.7 h·wk−1; 91.8 ± 1.7 vs 86.1 ± 1.8% O2max), presented a continuous PaO2 decrease up to O2max. This was associated with a widening (Ai-a)DO2.

Conclusion This study showed that a relative hypoventilation, probably induced by a high level of endurance training, induced hypoxemia in all athletes. However, a nonventilatory mechanism, perhaps related to the volume of training, seemed to affect gas exchanges beyond the second ventilatory threshold in the H athletes, thereby enhancing EIH.

Laboratoire de Physiologie des Interactions, Hôpital A. de Villeneuve, Montpellier, FRANCE

Submitted for publication September 1998.

Accepted for publication June 1999.

Address for correspondence: Fabienne Durand, Laboratoire de Physiologie des Interactions, Service EFR, Hôpital Arnaud de Villeneuve, 34295 Montpellier Cedex 5, France. E-mail: physio34@aol.com.

© 2000 Lippincott Williams & Wilkins, Inc.