Bryant Adam L, Pua Yong-Hao, Clark Ross A
Centre for Health, Exercise and Sports Medicine, School of Physiotherapy, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia.
J Bone Joint Surg Am. 2009 Jun;91(6):1424-31. doi: 10.2106/JBJS.H.01335.
Mechanical instability, neurosensory deficits, and/or modified coactivation strategies following anterior cruciate ligament injury and surgery might compromise the ability of the knee extensors to exert a precise force during isokinetic knee extension with maximal effort. The purpose of this study was to examine the effects of an anterior cruciate ligament deficiency and reconstruction on knee extensor torque-time curve smoothness and to elucidate its association with hamstring (antagonist) activation and physical performance.
Thirteen subjects who had a unilateral deficiency of the anterior cruciate ligament, twenty-five matched subjects with a unilateral reconstructed anterior cruciate ligament, and thirty-three control subjects performed knee extension and flexion repetitions bilaterally with maximal effort at 180 degrees/sec on a Cybex dynamometer. For the subjects with a deficient or a reconstructed anterior cruciate ligament, hamstring activation was measured electromyographically. Physical performance was measured by requiring subjects to perform single-limb timed hopping on the involved limb.
In the subjects with a reconstructed or a deficient anterior cruciate ligament, wavelet-derived mean instantaneous frequency of the extensor torque-time curves was significantly (p < 0.001) higher in the involved limb than in the noninvolved limb and the limbs of the control subjects. Furthermore, for the subjects with a reconstructed or deficient anterior cruciate ligament, the mean instantaneous frequency of the extensor torque-time curves was positively associated with the level of hamstring antagonist activity (r = 0.580, p < 0.001) and with hopping performance (b = -0.943, p = 0.019), whereas isokinetic peak torque was not (b = -0.001, p = 0.797).
For individuals who have a deficient or a reconstructed anterior cruciate ligament, an increased frequency content of the knee extensor torque is not, as previously and commonly assumed, a deleterious manifestation of the neuromuscular system. Rather, our results suggest that torque smoothness reduces as hamstring activation increases-a positive neuromuscular adaptation that enhances joint stability and, hence, optimizes physical performance. Wavelet-derived measures of extensor torque smoothness may provide valuable clinical information regarding joint function that conventional isokinetic torque measures cannot.
前交叉韧带损伤及手术后出现的机械性不稳定、神经感觉功能障碍和/或改变的共同激活策略，可能会损害膝关节伸肌在最大努力进行等速膝关节伸展时精确发力的能力。本研究的目的是探讨前交叉韧带缺损与重建对膝关节伸肌扭矩-时间曲线平滑度的影响，并阐明其与腘绳肌（拮抗肌）激活及身体功能的关系。
13名单侧前交叉韧带缺损的受试者、25名单侧前交叉韧带重建的匹配受试者以及33名对照受试者在Cybex测力计上以180度/秒的速度双侧最大努力进行膝关节伸展和屈曲重复动作。对于前交叉韧带缺损或重建的受试者，通过肌电图测量腘绳肌激活情况。通过要求受试者在患侧肢体上进行单腿定时跳跃来测量身体功能。
在前交叉韧带重建或缺损的受试者中，患侧肢体伸肌扭矩-时间曲线的小波衍生平均瞬时频率显著高于（p < 0.001）对侧肢体及对照受试者的肢体。此外，对于前交叉韧带重建或缺损的受试者，伸肌扭矩-时间曲线的平均瞬时频率与腘绳肌拮抗肌活动水平呈正相关（r = 0.580，p < 0.001），与跳跃表现也呈正相关（b = -0.943，p = 0.019），而异速峰值扭矩则不然（b = -0.001，p = 0.797）。
对于前交叉韧带缺损或重建的个体，膝关节伸肌扭矩频率成分增加并非如先前普遍认为的那样是神经肌肉系统的有害表现。相反，我们的结果表明，随着腘绳肌激活增加，扭矩平滑度降低——这是一种积极的神经肌肉适应，可增强关节稳定性，从而优化身体功能。基于小波分析的伸肌扭矩平滑度测量可能提供有关关节功能的有价值临床信息，而传统的等速扭矩测量则无法做到。
