Jeffery Mador M, Kufel T J, Pineda L A
Division of Pulmonary and Critical Care Medicine, State University of New York at Buffalo, Buffalo, New York, USA.
Am J Respir Crit Care Med. 2000 Nov;162(5):1760-6. doi: 10.1164/ajrccm.162.5.2001005.
The purpose of this study was to determine whether quadriceps or diaphragmatic fatigue or both occur after high-intensity cycle exercise to exhaustion in healthy elderly persons. Ten relatively sedentary male subjects aged 68.3 +/- 1.4 yr (mean +/- SE) (range: 60 to 75 yr) exercised at 65% to 75% of their predetermined maximal work capacity to the limits of tolerance on two separate days. On one occasion, quadriceps twitch force (Q(tw)) was measured during magnetic stimulation of the femoral nerve. On the other occasion, twitch transdiaphragmatic pressure (Pdi(tw)) was measured during bilateral stimulation of the phrenic nerves. Because potentiated twitches may be more sensitive for detecting fatigue, both unpotentiated and potentiated (obtained 5 s after a 5-s maximum voluntary muscle contraction) twitches were measured before and at 10, 30, and 60 min after exercise. During constant-load exercise, subjects exercised at 75 +/- 7 W for 21.9 +/- 1.8 min during the quadriceps studies, and for 17.7 +/- 1.9 min during the diaphragm studies. Peak V O(2) was 1.58 +/- 0.08 L/min during both studies. Pdi(tw) (unpotentiated and potentiated) was not significantly different from baseline at any time after exercise. Unpotentiated Q(tw) was significantly decreased after exercise, to 64.0 +/- 6.3% of the baseline value at 10 min after exercise (p < 0.0003), and remained significantly decreased at 30 min after exercise. Potentiated Q(tw) was also significantly decreased after exercise, to 63.5 +/- 2.7% of the baseline value at 10 min after exercise (p < 0.0001), and remained significantly decreased at 30 and 60 min after exercise. In conclusion, high-intensity cycle exercise to exhaustion results in significant contractile fatigue of the quadriceps muscle but not of the diaphragm in healthy, relatively sedentary, elderly subjects.
本研究的目的是确定在健康老年人进行高强度自行车运动直至力竭后，股四头肌或膈肌疲劳或两者是否会出现。10名相对久坐不动的男性受试者，年龄为68.3±1.4岁（平均±标准误）（范围：60至75岁），在两天内分别以其预定最大工作能力的65%至75%进行运动，直至耐受极限。在其中一次运动时，在对股神经进行磁刺激期间测量股四头肌抽搐力（Q(tw)）。在另一次运动时，在对双侧膈神经进行刺激期间测量跨膈抽搐压（Pdi(tw)）。由于增强抽搐可能对检测疲劳更敏感，因此在运动前以及运动后10、30和60分钟测量未增强和增强的（在5秒最大自主肌肉收缩后5秒获得）抽搐。在恒负荷运动期间，在股四头肌研究中，受试者以75±7瓦的功率运动21.9±1.8分钟，在膈肌研究中运动17.7±1.9分钟。两项研究期间的峰值V O(2)均为1.58±0.08升/分钟。运动后任何时间，Pdi(tw)（未增强和增强的）与基线相比均无显著差异。未增强的Q(tw)在运动后显著降低，运动后10分钟降至基线值的64.0±6.3%（p<0.0003），在运动后30分钟仍显著降低。增强的Q(tw)在运动后也显著降低，运动后10分钟降至基线值的63.5±2.7%（p<0.0001），在运动后30和60分钟仍显著降低。总之，在健康、相对久坐的老年受试者中，高强度自行车运动直至力竭会导致股四头肌明显的收缩性疲劳，但不会导致膈肌疲劳。
