Young P M, Sutton J R, Green H J, Reeves J T, Rock P B, Houston C S, Cymerman A
Altitude Physiology and Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760.
J Appl Physiol (1985). 1992 Dec;73(6):2574-9. doi: 10.1152/jappl.1992.73.6.2574.
The reasons for the reduced exercise capacities observed at high altitudes are not completely known. Substrate availability or accumulations of lactate and ammonium could have significant roles. As part of Operation Everest II, peak oxygen uptakes were determined in five normal male volunteers with use of progressively increasing cycling work loads at ambient barometric pressures of 760, 380, and 282 Torr. Decrements from sea level (SL) to 380 and 282 Torr occurred in peak power output (19 and 47%), time to exhaustion (19 and 48%), and oxygen uptake (41 and 61%), respectively. Arterial saturations after exhaustive exercise were decreased to 63% at 380 Torr and 39% at 282 Torr. At 380 and 282 Torr, postexercise plasma concentrations of glucose and free fatty acids were not increased, whereas plasma glycerol concentrations were decreased relative to SL (145 +/- 24 microM at 380 Torr and 77 +/- 10 microM at 282 Torr vs. 213 +/- 24 microM at SL). Preexercise plasma insulin concentrations were elevated at both 380 and 282 Torr (87 +/- 16 pM at 380 Torr and 85 +/- 18 pM at 282 Torr vs. 41 +/- 30 pM at SL). In general, postexercise concentrations of plasma catecholamines were decreased at altitude compared with SL. Preexercise lactate and ammonium concentrations were not different at any simulated altitude. From these data neither substrate availability nor metabolic product accumulation limited exercise capacity at extreme simulated altitude.
在高海拔地区观察到运动能力下降的原因尚不完全清楚。底物可用性或乳酸和铵的积累可能起着重要作用。作为“珠穆朗玛峰行动II”的一部分，在环境气压为760、380和282托时，通过逐渐增加自行车运动负荷，测定了五名正常男性志愿者的峰值摄氧量。从海平面（SL）到380和282托时，峰值功率输出分别下降了19%和47%，疲劳时间分别下降了19%和48%，摄氧量分别下降了41%和61%。力竭运动后的动脉血氧饱和度在380托时降至63%，在282托时降至39%。在380和282托时，运动后血浆葡萄糖和游离脂肪酸浓度没有增加，而血浆甘油浓度相对于海平面下降（380托时为145±24微摩尔/升，282托时为77±10微摩尔/升，而海平面时为213±24微摩尔/升）。运动前血浆胰岛素浓度在380和282托时均升高（380托时为87±16皮摩尔/升，282托时为85±18皮摩尔/升，而海平面时为41±30皮摩尔/升）。一般来说，与海平面相比，高海拔地区运动后血浆儿茶酚胺浓度降低。在任何模拟海拔高度下，运动前乳酸和铵浓度均无差异。根据这些数据，在极端模拟海拔高度下，底物可用性和代谢产物积累均未限制运动能力。
