Prevalence of Exercise-Induced Arterial Hypoxemia in Distance Runners at Sea Level

Purpose It has been reported that 50% of endurance-trained men demonstrate exercise-induced arterial hypoxemia (EIAH) during heavy exercise. However, this often-cited prevalence rate comes from a single study using a cohort of 25 highly trained men who completed maximal cycle ergometry. As arterial oxyhemoglobin saturation (SpO 2) during maximal exercise is reported to be significantly lower during treadmill versus cycle ergometry in the same subjects, we hypothesized that the prevalence of EIAH would be greater than previously reported (and commonly referenced) in a larger cohort of highly endurance-trained men during maximal treadmill running. Methods Data from 124 highly trained male distance runners (VO 2max range = 60.3-84.7 mL·kg -1 ·min -1) were retrospectively examined from previously published studies completed in the Indiana University Human Performance Laboratory. Subjects completed a constant speed, progressive-grade treadmill exercise test to volitional exhaustion, and arterial oxyhemoglobin saturation (SaO 2ear) in all subjects was estimated using the same oximeter (Hewlett Packard 47201A). Results Using similar inclusion criteria as previously published for highly trained (VO 2max > 68 mL·kg -1 ·min -1) and for EIAH (SaO 2ear ≤ 91%), 55 of 79 subjects (70%) exhibited exercise-induced arterial desaturation. Across all 124 subjects, 104 (84%) demonstrated at least moderate EIAH (SaO 2ear ≤ 93%) during maximal treadmill exercise. SaO 2ear was significantly yet weakly correlated with VE/VO 2 (P < 0.01, r = 0.28) and VE/VCO 2 (P < 0.001, r = 0.33) but not with VO 2max. Conclusion These results indicate that the prevalence of EIAH in highly trained men during maximal treadmill exercise at sea level is greater compared with previously suggested data, with exercise mode perhaps playing a factor in the number of athletes who experience EIAH.