Institute of Sports Sciences, University of Lausanne, Lausanne, Switzerland.
Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado, Colorado Springs, Colorado, United States.
J Appl Physiol (1985). 2023 Oct 1;135(4):823-832. doi: 10.1152/japplphysiol.00100.2023. Epub 2023 Aug 17.
Acute altitude exposure lowers arterial oxygen content ([Formula: see text]) and cardiac output ([Formula: see text]) at peak exercise, whereas O extraction from blood to working muscles remains similar. Acclimatization normalizes [Formula: see text] but not peak [Formula: see text] nor peak oxygen consumption (V̇o). To what extent acclimatization impacts muscle O extraction remains unresolved. Twenty-one sea-level residents performed an incremental cycling exercise to exhaustion near sea level (SL), in acute (ALT1) and chronic (ALT16) hypoxia (5,260 m). Arterial blood gases, gas exchange at the mouth and oxy- (OHb) and deoxyhemoglobin (HHb) of the vastus lateralis were recorded to assess arterial O content ([Formula: see text]), [Formula: see text], and V̇o. The HHb-V̇o slope was taken as a surrogate for muscle O extraction. During moderate-intensity exercise, HHb-V̇o slope increased to a comparable extent at ALT1 (2.13 ± 0.94) and ALT16 (2.03 ± 0.88) compared with SL (1.27 ± 0.12), indicating increased O extraction. However, the HHb/[Formula: see text] ratio increased from SL to ALT1 and then tended to go back to SL values at ALT16. During high-intensity exercise, HHb-V̇o slope reached a break point beyond which it decreased at SL and ALT1, but not at ALT16. Increased muscle O extraction during submaximal exercise was associated with decreased [Formula: see text] in acute hypoxia. The significantly greater muscle O extraction during maximal exercise in chronic hypoxia is suggestive of an O reserve. During incremental exercise muscle deoxyhemoglobin (HHb) and oxygen consumption (V̇o) both increase linearly, and the slope of their relationship is an indirect index of local muscle O extraction. The latter was assessed at sea level, in acute and during chronic exposure to 5,260 m. The demonstrated presence of a muscle O extraction reserve during chronic exposure is coherent with previous studies indicating both limited muscle oxidative capacity and decrease in motor drive.
急性高原暴露会降低运动峰值时的动脉血氧含量 ([Formula: see text]) 和心输出量 ([Formula: see text])，而血液向工作肌肉的氧提取仍保持相似。适应会使 [Formula: see text] 正常化，但不会使峰值 [Formula: see text] 或峰值耗氧量 (V̇o) 正常化。适应在多大程度上影响肌肉氧提取仍未解决。21 名海平面居民在海平面 (SL) 附近进行了急性 (ALT1) 和慢性 (ALT16) 缺氧 (5,260 m) 时的递增式自行车运动至力竭。记录动脉血气、口腔气体交换以及股外侧肌的氧合 (OHb) 和脱氧血红蛋白 (HHb)，以评估动脉血氧含量 ([Formula: see text])、[Formula: see text] 和 V̇o。HHb-V̇o 斜率被用作肌肉氧提取的替代指标。在中等强度运动时，HHb-V̇o 斜率在 ALT1 (2.13±0.94) 和 ALT16 (2.03±0.88) 与 SL (1.27±0.12) 相比增加到相似程度，表明氧提取增加。然而，HHb/[Formula: see text] 比值从 SL 增加到 ALT1，然后在 ALT16 时趋于回到 SL 值。在高强度运动时，HHb-V̇o 斜率在 SL 和 ALT1 时达到一个转折点，然后下降，但在 ALT16 时没有下降。在急性缺氧时，亚极量运动中的肌肉氧提取增加与 [Formula: see text] 降低有关。在慢性缺氧时，最大运动中肌肉氧提取显著增加提示存在氧储备。在递增运动中，肌肉脱氧血红蛋白 (HHb) 和耗氧量 (V̇o) 都呈线性增加，它们之间的关系斜率是局部肌肉氧提取的间接指标。在海平面、急性和慢性暴露于 5,260 m 时评估了后者。在慢性暴露时存在肌肉氧提取储备的证明与之前表明肌肉氧化能力有限和运动驱动下降的研究结果一致。
