Pulmonary gas exchange during exercise in women: effects of exercise type and work increment

1 Division of Physiology, Department of Medicine, University of California, San Diego, La Jolla 92093; and 2 Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, California 92350 Exercise-induced arterial hypoxemia (EIAH) has been reported in male athletes, particularly during fast-increment treadmill exercise protocols. Recent reports suggest a higher incidence in women. We hypothesized that 1-min incremental (fast) running (R) protocols would result in a lower arterial P O 2 (Pa O 2 ) than 5-min increment protocols (slow) or cycling exercise (C) and that women would experience greater EIAH than previously reported for men. Arterial blood gases, cardiac output, and metabolic data were obtained in 17 active women [mean maximal O 2 uptake ( O 2 max ) = 51 ml · kg 1 · min 1 ]. They were studied in random order (C or R), with a fast O 2 max protocol. After recovery, the women performed 5 min of exercise at 30, 60, and 90% of O 2 max (slow). One week later, the other exercise mode (R or C) was similarly studied. There were no significant differences in O 2 max between R and C. Pulmonary gas exchange was similar at rest, 30%, and 60% of O 2 max . At 90% of O 2 max , Pa O 2 was lower during R (mean ± SE = 94 ± 2 Torr) than during C (105 ± 2 Torr, P