The Effect Of Exercise-induced Hypoxemia On Immune Responses Among Endurance-trained Athletes

Exercise-induced hypoxemia (EIH; fall in oxyhemoglobin saturation (SpO2) > 4% during exercise) is highly prevalent in endurance athletes during heavy-intensity exercise and is associated with impaired performance. Yet, the physiological consequences of EIH during prolonged exercise are not fully understood. PURPOSE: To determine whether endurance-trained athletes who develop EIH experience more pronounced increases in immune markers following a 30-min bout of heavy-intensity exercise compared to those without EIH. METHODS: Fourteen endurance-trained athletes (Females = 2, age = 28.8 ± 6.3 yr, weight = 64.3 ± 7.3 kg, VO2max = 60.3 ± 7.5 ml/kg/min) with normal resting pulmonary function completed a 30-min constant-speed run at half-marathon pace (TEMP). Heart rate, ventilatory measures, and SpO2 were measured throughout TEMP. Blood samples for immune markers were taken at baseline (BL), immediately- (IP), 30 min-, 120 min- and 24 hr-post (P) exercise. RESULTS: While speed and %VO2max during TEMP were similar in EIH (15.9 ± 1.1 km/h & 87 ± 5%, respectively) and Non-EIH (15.2 ± 2.2 km/h & 88 ± 4%, respectively), mean SpO2 during TEMP was significantly (p < 0.05) lower in the EIH group (n = 7, range: 92 ± 3% compared to the Non-EIH group (n = 7, 95 ± 1%). Multivariate analysis showed significant (p < 0.05) group effects for ventilation as % of maximal ventilation (VE/VEmax; F = 13.10) and ventilatory equivalents for CO2 production (VE/VCO2; F = 25.14) during TEMP (avg. difference between EIH & Non-EIH: 8 ± 1%, 3.3 ± 0.6 for VE/VEmax & VE/VCO2, respectively). There were significant (p < 0.05) time effects for lymphocytes (LYM), neutrophils (NEU), and monocytes (F = 6.56, 10.18, & 4.44, respectively), with no group effects. LYM peaked IP and were significantly (p < 0.05) higher IP than at all time-points thereafter within each group (∆0.7 – 1.3 103/μL). In EIH, LYM were significantly (p < 0.05) reduced below BL at 30 min-24 hr-P. NEU were higher (p < 0.05) at 120 min-P than BL, 30 min- and 24 hr-P TEMP within each group (∆1.7 – 3.37 103/μL). Monocytes in both groups reached a nadir at 30 min-P, and then significantly (p < 0.05) increased at 120 min-P (∆0.1 – 0.2 103/μL). CONCLUSION: Although experiencing desaturation for ~30 min, perturbations in immune markers were not greater in EIH athletes compared to athletes without EIH following TEMP protocol.