Fulco C S, Cymerman A, Muza S R, Rock P B, Pandolf K B, Lewis S F
Altitude Physiology and Medicine Division, US Army Research Institute of Environmental Medicine, Natick 01760-5007.
J Appl Physiol (1985). 1994 Jul;77(1):179-83. doi: 10.1152/jappl.1994.77.1.179.
Large muscle exercise performance is impaired during acute exposure to normobaric or hypobaric hypoxia, but the effects of hypoxic conditions on fatigue of isolated smaller muscle groups per se are poorly defined. We studied how acute and chronic altitude (ALT) exposure and post-ALT return to sea level (SL) affects voluntary strength and fatigue of the adductor pollicis muscle. Eight healthy men (mean age 28 yr) were studied on five separate occasions: at SL, on days 1 (acute) and 13 (chronic) at ALT (4,300 m), and on days 1 (post 1) and 3 or 4 (post 2) at SL after 20 days of residence at ALT. On each day, maximal voluntary contractions (MVCs) of the adductor pollicis were obtained before and at the end of each minute of submaximal intermittent contractions of the adductor pollicis (50% of MVC of rested muscle, 5 s of contraction/5 s of rest) until exhaustion, defined as the inability to exert or maintain 50% of rested MVC. MVC of rested muscle did not differ among days. Time to exhaustion was shorter at acute ALT [5.1 +/- 0.5 (SE) min] than at SL (7.4 +/- 0.8 min, P < 0.05) and tended to be shorter than at chronic ALT (6.6 +/- 0.7 min, P > 0.05). Compared with acute and chronic ALT, time to exhaustion was prolonged during post 1 (9.0 +/- 1.2 min, P < 0.05) but not post 2 (6.1 +/- 0.5 min, P > 0.05). We conclude that 1) MVC of rested adductor pollicis muscle is not impaired during or after ALT exposure, 2) compared with SL conditions, acute but not chronic ALT exposure leads to a more rapid decline in adductor pollicis MVC associated with submaximal contractions, and 3) time to exhaustion is prolonged for > or = 1 day after return from ALT.
在急性暴露于常压或低压缺氧环境时，大肌肉群的运动表现会受损，但缺氧条件对孤立的较小肌肉群疲劳本身的影响尚不明确。我们研究了急性和慢性海拔（ALT）暴露以及从高海拔返回海平面（SL）后，对拇收肌的随意力量和疲劳有何影响。对8名健康男性（平均年龄28岁）在五个不同时间点进行了研究：在海平面、海拔4300米处的第1天（急性）和第13天（慢性），以及在海拔居住20天后返回海平面的第1天（返回后1）和第3或4天（返回后2）。每天，在拇收肌进行次最大间歇性收缩（静息肌肉最大随意收缩力[MVC]的50%，收缩5秒/休息5秒）直至疲劳（定义为无法施加或维持静息MVC的50%）之前和结束时，获取拇收肌的最大随意收缩（MVC）。静息肌肉的MVC在各天之间没有差异。急性海拔暴露时的疲劳时间[5.1±0.5（标准误）分钟]比海平面时（7.4±0.8分钟，P<0.05）短，且倾向于比慢性海拔暴露时（6.6±0.7分钟，P>0.05）短。与急性和慢性海拔暴露相比，返回后1时疲劳时间延长（9.0±1.2分钟，P<0.05），但返回后2时没有（6.1±0.5分钟，P>0.05）。我们得出结论：1）在海拔暴露期间或之后，静息拇收肌的MVC没有受损；2）与海平面条件相比，急性而非慢性海拔暴露会导致与次最大收缩相关的拇收肌MVC更快下降；3）从海拔返回后，疲劳时间延长≥1天。
