The effect of hypoxia on pulmonary O2 uptake, leg blood flow and muscle deoxygenation during single-leg knee-extension exercise

被引:61
作者
DeLorey, DS
Shaw, CN
Shoemaker, JK
Kowalchuk, JM
Paterson, DH [1 ]
机构
[1] Univ Western Ontario, Sch Kinesiol, Canadian Ctr Activ & Aging, London, ON N6A 3K7, Canada
[2] Univ Western Ontario, Dept Physiol & Pharmacol, London, ON N6A 3K7, Canada
关键词
D O I
10.1113/expphysiol.2003.026864
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
The effect of hypoxic breathing on pulmonary O-2 uptake VO2p), leg blood flow (LBF) and O-2 delivery and deoxygenation of the vastus lateralis muscle was examined during constant-load single-leg knee-extension exercise. Seven subjects (24 4 years; mean S.D.) performed two transitions from unloaded to moderate-intensity exercise (21 W) under normoxic and hypoxic (PETO2 = 60 mmHg) conditions. Breath-by-breath VO2p and beat-by-beat femoral artery mean blood velocity (MBV) were measured by mass spectrometer and volume turbine and Doppler ultrasound (VingMed, CFM 750), respectively. Deoxy-(HHb), oxy-, and total haemoglobin/myoglobin were measured continuously by near-infrared spectroscopy (NIRS; Hamamatsu NIRO-300). VO2p data were filtered and averaged to 5 s bins at 20, 40, 60, 120, 180 and 300 s. MBV data were filtered and averaged to 2 s bins (I contraction cycle). LBF was calculated for each contraction cycle and averaged to 5 s bins at 20, 40, 60, 120, 180 and 300 s. VO2p was significantly lower in hypoxia throughout the period of 20, 40, 60 and 120 s of the exercise on-transient. LBF (1 min(-1)) was approximately 35% higher (P >,0.05) in hypoxia during the on-transient and steady-state of KE exercise, resulting in a similar leg O-2 delivery in hypoxia and normoxia. Local muscle deoxygenation (HHb) was similar in hypoxia and normoxia. These results suggest that factors other than O-2 delivery, possibly the diffusion of O-2, were responsible for the lower O-2 uptake during the exercise on-transient in hypoxia.
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页码:293 / 302
页数:10
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