School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney , New South Wales , Australia.
Neuroscience Research Australia (NeuRA), Sydney, New South Wales , Australia.
J Appl Physiol (1985). 2019 Jul 1;127(1):229-234. doi: 10.1152/japplphysiol.00168.2019. Epub 2019 May 23.
When assessing passive joint range of motion in neurological conditions, concomitant involuntary muscle activity is generally regarded small enough to ignore. This assumption is untested. If false, many clinical and laboratory studies that rely on these assessments may be in error. We determined to what extent small amounts of involuntary muscle activity limit passive range of motion in 30 able-bodied adults. Subjects were seated with the knee flexed 90° and the ankle in neutral, and predicted maximal plantarflexion torque was determined using twitch interpolation. Next, with the knee flexed 90° or fully extended, the soleus muscle was continuously electrically stimulated to generate 1, 2.5, 5, 7.5, and 10% of predicted maximal torque, in random order, while the ankle was passively dorsiflexed to a torque of 9 N·m by a blinded investigator. A trial without stimulation was also performed. Ankle dorsiflexion torque-angle curves were obtained at each percent of predicted maximal torque. On average (mean, 95% confidence interval), each 1% increase in plantarflexion torque decreases ankle range of motion by 2.4° (2.0 to 2.7°; knee flexed 90°) and 2.3° (2.0 to 2.5°; knee fully extended). Thus 5% of involuntary plantarflexion torque, the amount usually considered small enough to ignore, decreases dorsiflexion range of motion by ~12°. Our results indicate that even small amounts of involuntary muscle activity will bias measures of passive range and hinder the differential diagnosis and treatment of neural and nonneural mechanisms of contracture. The soleus muscle in able-bodied adults was tetanically stimulated while the ankle was passively dorsiflexed. Each 1% increase in involuntary plantarflexion torque at the ankle decreases the range of passive movement into dorsiflexion by >2°. Thus the range of ankle dorsiflexion decreases by ~12° when involuntary plantarflexion torque is 5% of maximum, a torque that is usually ignored. Thus very small amounts of involuntary muscle activity substantially limit passive joint range of motion.
在评估神经状况下的被动关节活动范围时，通常认为伴随的非自愿肌肉活动小到可以忽略不计。这种假设未经检验。如果是错误的，那么许多依赖这些评估的临床和实验室研究可能存在误差。我们旨在确定在 30 名健康成年人中，少量的非自愿肌肉活动对被动运动范围的限制程度。受试者坐在座位上，膝盖弯曲 90°，脚踝中立，使用抽搐插值法确定最大预测跖屈扭矩。接下来，在膝盖弯曲 90°或完全伸展的情况下，连续用电刺激比目鱼肌，以产生预测最大扭矩的 1%、2.5%、5%、7.5%和 10%，顺序随机，同时由一名闭眼研究员将脚踝被动背屈至 9 N·m 的扭矩。还进行了一次没有刺激的试验。在每个预测最大扭矩的百分比下获得踝关节背屈扭矩-角度曲线。平均（平均值，95%置信区间），跖屈扭矩每增加 1%，踝关节活动范围减少 2.4°（90°弯曲的膝盖）和 2.3°（完全伸展的膝盖）。因此，通常认为小到可以忽略不计的 5%的非自愿跖屈扭矩会使背屈运动范围减少约 12°。我们的结果表明，即使是少量的非自愿肌肉活动也会影响被动运动范围的测量，并阻碍对神经和非神经挛缩机制的鉴别诊断和治疗。在健康成年人中，比目鱼肌被强直刺激，同时脚踝被动背屈。踝关节处非自愿跖屈扭矩每增加 1%，被动背屈运动范围减少>2°。因此，当非自愿跖屈扭矩达到最大扭矩的 5%时，即通常被忽略的扭矩，踝关节背屈范围减少约 12°。因此，非常少量的非自愿肌肉活动极大地限制了被动关节活动范围。
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