Impairment Of 3000m Racing Performance At Moderate Altitude Is Influenced By VO2 And SaO2 Maintenance

Abstract

Athletic competitions involving endurance exercise at moderate altitude are characterized by impaired performances compared to sea level. The decline in maximal oxygen uptake (VO2max) with acute exposure to moderate altitude has been shown to be dependent on both the magnitude of VO2max at sea level, as well as the ability to maintain arterial oxyhemoglobin saturation (SaO2) during exercise. Whether these relationships extend to influence racing performance with acute altitude exposure is unknown. PURPOSE: This study examined if SaO2 and VO2 maintenance during heavy exercise in acute hypoxia are related to the acute decline in racing performance of elite athletes at altitude. METHODS: Twenty-seven elite distance runners (18 M, 9 F, VO2max = 71.8 + 7.2 ml/kg/min) performed a treadmill exercise bout at a constant speed which simulated their 3000m race pace, both in normoxia (elevation 230m) and breathing 16.3 % O2 (simulating 2100m). Separate 3000m time trials were completed on 400m all-weather outdoor tracks at elevations of 230m (SL), 18 hrs prior to exposure to altitude, and 2100m (ALT), 48 hrs after arrival at altitude. Statistical significance was set at P < 0.05. RESULTS: Group 3000m time trial performance was significantly slower at ALT versus SL (D3000m race time = +48.5 + 12.7 s or 9.2%), and the declines in performances were similar in men (+48.4 + 14.6 s) and women (+48.6 + 8.9 s). Athletes grouped as low SaO2 during race pace treadmill running in normoxia (SaO2 < 91%, n = 7) had a significantly larger decline in race pace VO2 in hypoxia (-9.2 + 2.1 ml/kg/min) and slowing of 3000m race time at altitude (+54.0 + 13.7 s) compared to athletes grouped with high SaO2 during race pace running in normoxia (SaO2 > 93%, n = 7, DVO2 = -3.5 + 2.0 ml/kg/min, D3000m race time = +38.9 + 9.7 s). SaO2 during normoxic race pace running was significantly correlated with both the decline in VO2 from normoxia to hypoxia during race pace running (r = -0.68), as well as the decline in 3000m race time at ALT (r = -0.38). CONCLUSION: These results indicate that the degree of arterial oxyhemoglobin desaturation during heavy exercise, already known to influence the decline in VO2max at altitude, also contributes to the magnitude of the decline in racing performance with acute altitude exposure. Supported by a grant from the US Olympic Committee and USA Track and Field