Cerebrovascular responses to incremental exercise during hypobaric hypoxia: effect of oxygenation on maximal performance
Cerebrovascular responses to incremental exercise during hypobaric hypoxia: effect of oxygenation on maximal performance
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DOI：
10.1152/ajpheart.01104.2007
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发表时间：
2008-01-01
影响因子：
4.8
通讯作者：
Roach, Robert C.
中科院分区：
文献类型：
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作者：
Subudhi, Andrew W.;Lorenz, Matthew C.;Roach, Robert C.
我们试图描述脑血管对增量运动的反应，并验证脑氧合变化影响最大表现的假设。11人在三种条件下骑行：1)海平面（SL）；2)急性缺氧[AH；低压室，吸入PO2 (PIO2)86托[；3)慢性缺氧[CH；4300米，PIO2 86度]。在最大工作速率（W-max）下，吸入氧分数（FIO2）秘密增加到0.60，同时鼓励受试者继续踩踏板。分析脑（额叶）（C-OX）和肌肉（股外侧）氧合（M-OX）（近红外光谱）、大脑中动脉血流速度（MCA V-mean；经颅多普勒）和尾潮PCO2 （PETCO2）在%W-max范围内的变化（P < 0.05）。在SL， PETCO2， MCA Vmean和C-OX随着工作速率从75%上升到100% W-max而下降。在AH期间，PETCO2和MCA Vmean从50% W-max下降到100% W-max，而C-OX则从静止状态下降。使用CH， PETCO2和C-OX在整个运动过程中下降，而MCA Vmean仅从75%降至100% W-max。在静止状态下和静止状态下，M-OX从休息状态下降到75% W-max，在运动状态下，M-OX的下降幅度不同（CH > AH >sl），但M-OX的下降幅度不同。FIO2 0.60在w max时没有延长SL时的运动，但允许受试者在AH时持续96 +/- 61 s，在CH时持续162 +/- 90 s。在FIO2 0.60期间，随着工作速率的增加，C-OX升高，M-OX保持不变。因此，脑缺氧似乎对低气压缺氧期间的最大运动施加了限制（PIO2 86 Torr），因为它的逆转与表现的改善有关。
We sought to describe cerebrovascular responses to incremental exercise and test the hypothesis that changes in cerebral oxygenation influence maximal performance. Eleven men cycled in three conditions: 1) sea level (SL); 2) acute hypoxia [AH; hypobaric chamber, inspired PO2 (PIO2)86 Torr]; and 3) chronic hypoxia [CH; 4,300 m, PIO2 86 Torr]. At maximal work rate (W-max), fraction of inspired oxygen (FIO2) was surreptitiously increased to 0.60, while subjects were encouraged to continue pedaling. Changes in cerebral ( frontal lobe) (C-OX) and muscle (vastus lateralis) oxygenation (M-OX) ( near infrared spectroscopy), middle cerebral artery blood flow velocity (MCA V-mean; transcranial Doppler), and end-tidal PCO2 (PETCO2) were analyzed across %W-max (significance at P < 0.05). At SL, PETCO2, MCA Vmean, and C-OX fell as work rate rose from 75 to 100% W-max. During AH, PETCO2 and MCA Vmean declined from 50 to 100% W-max, while C-OX fell from rest. With CH, PETCO2 and C-OX dropped throughout exercise, while MCA Vmean fell only from 75 to 100% W-max. M-OX fell from rest to 75% W-max at SL and AH and throughout exercise in CH. The magnitude of fall in C-OX, but not M-OX, was different between conditions (CH > AH > SL). FIO2 0.60 at W. max did not prolong exercise at SL, yet allowed subjects to continue for 96 +/- 61 s in AH and 162 +/- 90 s in CH. During FIO2 0.60, C-OX rose and M-OX remained constant as work rate increased. Thus cerebral hypoxia appeared to impose a limit to maximal exercise during hypobaric hypoxia (PIO2 86 Torr), since its reversal was associated with improved performance.