Determinants of maximal oxygen uptake in moderate acute hypoxia in endurance athletes

Abstract

The factors determining maximal oxygen consumption were explored in eight endurance trained subjects (TS) and eight untrained subjects (US) exposed to moderate acute normobaric hypoxia. Subjects performed maximal incremental tests at sea level and simulated altitudes (1,000, 2,500, 4,500 m). Heart rate (HR), stroke volume (SV), cardiac output (.Q), arterialized oxygen saturation (Sa'O2), oxygen uptake (.VO2max), ventilation (.VE, expressed in normobaric conditions) were measured. At maximal exercise, ventilatory equivalent (.VE/.VO2max), O2 transport (.QaO2max) and O2 extraction (O2ERmax) were calculated. In TS, .Qmax remained unchanged despite a significant reduction in HRmax at 4,500 m. SVmax remained unchanged. .VEmax decreased in TS at 4,500 m, .VE/.VO2max was lower in TS and greater at 4,500 m vs. sea level in both groups. Sa'O2max decreased at and above 1,000 m in TS and 2,500 m in US, O2ERmax increased at 4,500 m in both groups. .QaO2max decreased with altitude and was greater in TS than US up to 2,500 m but not at 4,500 m. .VO2max decreased with altitude but the decrement (Delta.VO2max) was larger in TS at 4,500 m. In both groups Delta.VO2max in moderate hypoxia was correlated with Delta.QaO2max. Several differences between the two groups are probably responsible for the greater Delta.VO2max in TS at 4,500 m : (1) the relative hypoventilation in TS as shown by the decrement in .VEmax at 4,500 m (2) the greater.QaO2max decrement in TS due to a lower Sa'O2max and unchanged .Qmax 3) the smaller increase in O2ERmax in TS, insufficient to compensate the decrease in .QaO2max.

Effects of Acute Hypoxia at Moderate Altitude on Stroke Volume and Cardiac Output During Exercise

“…However, in those investigations, SV was measured at only several time-points during exercise. 3,4,17) Therefore, whether acute hypoxia at moderate altitude may alter the SV response during exercise has not been fully investigated.CO measurement by the impedance method has been improved and can be used to continuously monitor SV, andFrom the …”

“…Training at moderate altitude (corresponding to 2000 -3000 m) is associated with relatively severe hypoxemia during submaximal and maximal exercise, 1) and acute hypoxia of this level decreases VO 2 max as well as exercise capacity. [2][3][4] Thus, hypoxia at moderate altitude limits training intensity, which leads to relative deconditioning in elite athletes, although endurance athletes often use hypoxic training to improve sea-level performance. 5) Because VO 2 is the product of cardiac output (CO) and the arterio-venous oxygen content difference (C(a-v)O 2 ), a decrease in VO 2 max at maximal exercise may be due to a decrease of either factor, or both.…”

“…Although in previous studies researchers investigated the acute effect of hypoxia on the CO response during maximal and/or submaximal exercise at moderate altitude (corresponding to 2500 -3000 m), [2][3][4]16,17) in only three studies the SV response was examined during exercise. However, in those investigations, SV was measured at only several time-points during exercise.…”

Aclimatação em altitude simulada: efeitos sobre a frequência cardíaca e saturação de oxigênio da hemoglobina em jogadores de futebol

“…Alguns estudos (MOLLARD et al, 2007;WOORONS et al, 2005) têm mostrado que a diminuição do VO 2MÁX durante exposição aguda à altitude está diretamente relacionado à redução da saturação de oxigênio da hemoglobina (SpO 2 ). Além disso, a exposição aguda à altitude aumenta a frequência cardíaca (FC) de repouso e submáxima (BEIDLEMAN et al, 2003;ALARCÓN et al, 2012).…”

Análise da correlação entre o protocolo Polar Fitness Test® para predição de VO2máx e ergoespirometria

“…The importance of the oxygen maximum consumption ( O 2max ) measurement is justified by its international acceptance as the best physiological parameter for evaluation of the functional capacity of the cardiorespiratory system both in athletes 1,2 and in non-athletes who physically train with the goal to obtain better health 3 . Moreover, it has also been used as basis for the prescription of physical exercises in individuals with non-transmissible chronic diseases such as diabetes 4 .…”