Commentary on point-counterpoint: Positive effects of intermittent hypoxia (live high:train low) on exercise performance are/are not mediated primarily by augmented red cell volume.

To the Editor: Whether augmented red cell volume by intermittent hypoxia improves exercise performance is still controversial (4). Erythropoietin (Epo) synthesis is stimulated by hypoxia, and Epo is released during exercise-induced hypoxemia or when exercise is carried out under hypoxic conditions. Epo increases only temporarily at altitude, and aspartate aminotransferase activity in erythrocytes is augmented, indicating reduced mean cell age (1).