Elite endurance athletes display varying degrees of pulmonary gas exchange limitations during maximal normoxic exercise and many demonstrate reduced arterial O2 saturations (SaO2) at JOURNAL/mespex/04.02/00005768-199905000-00016/ENTITY_OV0312/v/2017-07-20T222700Z/r/image-pngO2max-a condition referred to as exercise induced arterial hypoxemia (EIH). We asked whether mild hypoxia would cause significant declines in SaO2 and JOURNAL/mespex/04.02/00005768-199905000-00016/ENTITY_OV0312/v/2017-07-20T222700Z/r/image-pngO2max in EIH athletes while non-EIH athletes would be unaffected.Methods:
Nineteen highly trained males were divided into EIH (N = 8) or Non-EIH (N = 6) groups based on SaO2 at JOURNAL/mespex/04.02/00005768-199905000-00016/ENTITY_OV0312/v/2017-07-20T222700Z/r/image-pngO2max (EIH < 90%, Non-EIH > 92%). Athletes with intermediate SaO2 values (N = 5) were only included in correlational analyses. Two randomized incremental treadmill tests to exhaustion were completed-one in normoxia, one in mild hypoxia (FIO2 = 0.187; ∼1,000m).Results:
EIH subjects demonstrated a significant decline in JOURNAL/mespex/04.02/00005768-199905000-00016/ENTITY_OV0312/v/2017-07-20T222700Z/r/image-pngO2max from normoxia to mild hypoxia (71.1 ± 5.3 vs 68.1 ± 5.0 mL·kg−1·min−1, P < 0.01), whereas the non-EIH group did not show a significant ΔJOURNAL/mespex/04.02/00005768-199905000-00016/ENTITY_OV0312/v/2017-07-20T222700Z/r/image-pngO2max (67.2 ± 7.6 vs 66.2 ± 8.4 mL·kg−1·min−1). For all 19 athletes, SaO2 during maximal exercise in normoxia correlated with the change in JOURNAL/mespex/04.02/00005768-199905000-00016/ENTITY_OV0312/v/2017-07-20T222700Z/r/image-pngO2max from normoxia to mild hypoxia (r = −0.54, P < 0.05). However, the change in SaO2 and arterial O2 content from normoxia to mild hypoxia was equal for both EIH and Non-EIH (ΔSaO2 = 5.2% for both groups), bringing into question the mechanism by which changes in SaO2 affect JOURNAL/mespex/04.02/00005768-199905000-00016/ENTITY_OV0312/v/2017-07-20T222700Z/r/image-pngO2max in mild hypoxia.Conclusions:
We conclude that athletes who display reduced measures of SaO2 during maximal exercise in normoxia are more susceptible to declines in JOURNAL/mespex/04.02/00005768-199905000-00016/ENTITY_OV0312/v/2017-07-20T222700Z/r/image-pngO2max in mild hypoxia compared with normoxemic athletes.