Cole M A, Brown M D
School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, UK.
Eur J Appl Physiol. 2000 May;82(1-2):39-44. doi: 10.1007/s004210050649.
The changes in muscle force associated with varying degrees of lower-limb ischaemia were investigated. Isometric torque production by the triceps surae muscle was measured during a 5-min continuous train of 2-Hz electrical stimulation in six healthy young adults under different thigh cuff occlusion pressures. The reproducibility of this protocol when performed under complete ischaemia (tested five times over a 2-week period) was assessed as having a coefficient of variation (CV) for fatigue (end/initial force) of [mean (SEM) 12 (1)%; n = 5]. This compares favourably with that obtained for maximum voluntary contraction torque [CV 9 (1)%]. In six subjects, triceps surae muscle fatigue was assessed under thigh cuff pressures of 0, 6.7 kPa (50 mmHg, venous occlusion) and 28 kPa (210 mmHg, complete ischaemia), as well as two intermediate levels of occlusion that were established by cuff pressures of 13.4 (0.5) and 20.3 (1.1) kPa [103 (4) and 152 (8) mmHg, respectively]. These corresponded to ankle-brachial pressure indices of 1.3 and 0.8, respectively when subjects were seated, or 0.8 and 0.36 when supine. With undisturbed lower-leg circulation, force potentiated steadily over the 5 min of stimulation such that the final force was 135 (8)% of the initial value. With complete ischaemia, force fell to 47 (2)% of the initial value. Stimulation under thigh occlusion pressures of 6.7, 13.4 and 20.3 kPa elicited intermediate levels of reduction in force, graded according to the increasing restriction of perfusion. The results show that low-force twitch contractions, which themselves do not occlude blood flow, are extremely sensitive to impaired perfusion and may represent a viable alternative to established methods of muscle performance assessment in patients with blood flow insufficiency.
研究了与不同程度下肢缺血相关的肌肉力量变化。在六名健康年轻成年人中，于不同大腿袖带阻断压力下，在2赫兹电刺激的5分钟连续训练过程中测量了腓肠肌的等长扭矩产生。当在完全缺血条件下执行该方案时（在2周内测试5次），评估其疲劳（终末/初始力量）的变异系数（CV）为[平均值（标准误）12（1）%；n = 5]。这与最大自主收缩扭矩的CV[9（1）%]相比更优。在六名受试者中，在0、6.7 kPa（50 mmHg，静脉阻塞）和28 kPa（210 mmHg，完全缺血）的大腿袖带压力下，以及由13.4（0.5）和20.3（1.1）kPa[分别为103（4）和152（8）mmHg]的袖带压力建立的两个中间阻塞水平下，评估了腓肠肌疲劳。当受试者坐着时，这些分别对应于踝臂压力指数1.3和0.8，或仰卧时为0.8和0.36。在小腿循环未受干扰的情况下，力量在5分钟的刺激过程中稳步增强，使得最终力量为初始值的135（8）%。在完全缺血时，力量降至初始值的47（2）%。在6.7、13.4和20.3 kPa的大腿阻塞压力下进行刺激会引起力量的中间程度降低，根据灌注受限程度增加而分级。结果表明，本身不阻塞血流的低强度抽搐收缩对灌注受损极其敏感，并且可能是血流不足患者中现有肌肉性能评估方法的可行替代方案。
