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

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• 作者：Pascal Mollard ; Xavier Woorons ; Muriel Letournel ; Christine Lamberto ; Fabrice Favret ; Aurélien Pichon ; Michèle Beaudry and Jean-Paul Richalet
• 关键词：Aerobic performance ; Cardiac output ; Arterial O2 saturation ; Venous O2 saturation ; Tissue O2 extraction
• 刊名：European Journal of Applied Physiology
• 出版年：2007
• 出版时间：August, 2007
• 年：2007
• 卷：100
• 期：6
• 页码：663-673
• 全文大小：448 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Biomedicine
  Human Physiology
  Occupational and Industrial Medicine
  Sports Medicine
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1439-6327

文摘

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)\dot]),{(\dot{{Q}})}, arterialized oxygen saturation (Sa￠O₂),{(\hbox{Sa}^{\prime}\hbox{O}_2)}, oxygen uptake ([(V)\dot]O_2max),{(\dot{{V}}\hbox{O}_{\rm 2max})}, ventilation ([(V)\dot]E,{\dot{{V}}{E}}, expressed in normobaric conditions) were measured. At maximal exercise, ventilatory equivalent ([(V)\dot]E/[(V)\dot]O_2max), O₂{(\dot{{V}}{E}/\dot{{V}}\hbox{O}_{\rm 2max}),\, \hbox{O}_2} transport ([(Q)\dot]aO_2max){(\dot{{Q}}\hbox{aO}_{\rm 2max})} and O₂ extraction (O₂ER_max) were calculated. In TS, [(Q)\dot]_max{\dot{{Q}}_{\rm max}} remained unchanged despite a significant reduction in HR_max{\hbox{HR}_{\rm max}} at 4,500 m. SV_max remained unchanged. [(V)\dot]E_max{\dot{{V}}{E}_{\rm max}} decreased in TS at 4,500 m, [(V)\dot]E/[(V)\dot]O_2max{\dot{{V}}{E}/\dot{{V}}\hbox{O}_{\rm 2max}} was lower in TS and greater at 4,500 m vs. sea level in both groups. Sa′O_2max decreased at and above 1,000 m in TS and 2,500 m in US, O₂ER_max increased at 4,500 m in both groups. [(Q)\dot]aO_2max{\dot{{Q}}\hbox{aO}_{\rm 2max}} decreased with altitude and was greater in TS than US up to 2,500 m but not at 4,500 m. [(V)\dot]O_2max{\dot{{V}}\hbox{O}_{\rm 2max}} decreased with altitude but the decrement (D[(V)\dot]O_2max){(\Delta \dot{{V}}\hbox{O}_{\rm 2max})} was larger in TS at 4,500 m. In both groups D[(V)\dot]O_2max{\Delta \dot{{V}}\hbox{O}_{\rm 2max}} in moderate hypoxia was correlated with D[(Q)\dot]aO_2max.{\Delta \dot{{Q}}\hbox{aO}_{\rm 2max}}. Several differences between the two groups are probably responsible for the greater D[(V)\dot]O_2max{\Delta \dot{{V}}\hbox{O}_{\rm 2max}} in TS at 4,500 m : (1) the relative hypoventilation in TS as shown by the decrement in [(V)\dot]E_max{\dot{{V}}{E}_{\rm max}} at 4,500 m (2) the greater [(Q)\dot]aO_2max{\dot{{Q}}\hbox{aO}_{\rm 2max}} decrement in TS due to a lower Sa′O_2max and unchanged [(Q)\dot]_max{\dot{{Q}}_{\rm max}} 3) the smaller increase in O₂ER_max in TS, insufficient to compensate the decrease in [(Q)\dot]aO_2max.{\dot{{Q}}a\hbox{O}_{\rm 2max}}.