Lum Peter S, Patten Carolynn, Kothari Dhara, Yap Ruth
Rehabilitation Research and Development Center, VA Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, California 94304-1200, USA.
Muscle Nerve. 2004 Dec;30(6):732-42. doi: 10.1002/mus.20157.
Impaired torque production is a major physical impairment following stroke, and has been studied extensively in isometric conditions. However, functional use of a limb requires torque production during movement, and the effects of velocity on maximal torque production may be abnormally enhanced in the paretic limb. The purpose of this study was to quantify the effects of movement velocity on maximal torque production during isokinetic, concentric flexion and extension of the elbow in poststroke subjects. Three speeds were tested (30, 75, 120 deg/s) over a 100-deg range of motion. To control for strength variations between subjects and limbs, isokinetic torques were normalized by peak isometric torque. As flexion velocity increased, paretic limb torque decreased at a greater rate than in the unaffected limb. During extension, paretic limb torque was much lower than torque in the unaffected limb at all speeds. In both flexion and extension, the disparity between limbs in the constant-velocity torque-angle curves became more pronounced as velocity increased. Torque decreased 44% +/- 7% in flexion and 63% +/- 9% in extension as velocity increased from 30 to 120 deg/s, whereas the corresponding decreases in the unaffected limb were only 9% +/- 5% in flexion and 16% +/- 4% in extension. No electromyographic (EMG) abnormalities were observed during flexion. During extension, EMG data provided evidence for abnormally increased antagonist coactivation in brachioradialis and markedly reduced activation in triceps as potential contributors to the decreased extension torques. The finding that movement velocity produces large deficits in maximal torque might explain why functional use of the paretic limb is often impaired even though isometric strength appears adequate.
扭矩产生受损是中风后的主要身体损伤，并且已经在等长条件下进行了广泛研究。然而，肢体的功能使用需要在运动过程中产生扭矩，并且速度对最大扭矩产生的影响在患侧肢体中可能异常增强。本研究的目的是量化运动速度对中风后受试者在等速、同心屈曲和伸展肘部过程中最大扭矩产生的影响。在100度的运动范围内测试了三种速度（30、75、120度/秒）。为了控制受试者和肢体之间的力量差异，等速扭矩通过峰值等长扭矩进行归一化。随着屈曲速度增加，患侧肢体扭矩下降的速率比未受影响的肢体更大。在伸展过程中，患侧肢体扭矩在所有速度下都远低于未受影响肢体的扭矩。在屈曲和伸展过程中，随着速度增加，恒速扭矩-角度曲线中肢体之间的差异变得更加明显。随着速度从30度/秒增加到120度/秒，屈曲时扭矩下降44%±7%，伸展时下降63%±9%，而未受影响肢体在屈曲和伸展时的相应下降仅分别为9%±5%和16%±4%。在屈曲过程中未观察到肌电图（EMG）异常。在伸展过程中，EMG数据提供了证据，表明肱桡肌中拮抗肌共激活异常增加，而肱三头肌激活明显减少，这可能是伸展扭矩下降的潜在原因。运动速度在最大扭矩方面产生巨大缺陷这一发现可能解释了为什么即使等长力量看起来足够，患侧肢体的功能使用仍常常受损。
