Elias Audrey R C, Hammill Curt D, Mizner Ryan L
School of Physical Therapy and Rehabilitation Sciences, University of Montana, Missoula, MT.
J Orthop Sports Phys Ther. 2015 Apr;45(4):273-80. doi: 10.2519/jospt.2015.5335. Epub 2015 Feb 13.
Pretest/posttest controlled laboratory study.
To determine changes in the neuromuscular activation of the quadriceps and hamstrings following instructions aimed at improving knee flexion during a single-limb landing task in persons who have undergone anterior cruciate ligament reconstruction (ACLR).
Clinicians advise patients who have undergone ACLR to increase knee flexion during landing tasks to improve impact attenuation. Another long-standing construct underlying such instruction involves increasing cocontraction of the hamstrings with the quadriceps to limit anterior shear of the tibia on the femur. The current study examined whether cocontraction of the knee musculature changes following instruction to increase knee flexion during landing.
Thirty-four physically active subjects with unilateral ACLR participated in a 1-time testing session. The kinetics and kinematics of single-leg landing on the surgical limb were analyzed before and after instruction to increase knee flexion and reduce the impact of landing. Vastus lateralis and biceps femoris activities were analyzed using surface electromyography and normalized to a maximal voluntary isometric contraction (MVIC). Cocontraction indices were integrated over the weight-acceptance phase of landing.
Following instruction, peak knee flexion increased (preinstruction mean ± SD, 56° ± 11°; postinstruction, 77° ± 12°; P<.001) and peak vertical ground reaction forces decreased (preinstruction, 3.50 ± 0.42 body mass; postinstruction, 3.06 ± 0.44 body mass; P<.001). Cocontraction also decreased following instruction (preinstruction, 30.88% ± 17.68% MVIC; postinstruction, 23.74% ± 15.39% MVIC; P<.001). The change in cocontraction was correlated with a decrease in hamstring activity (preinstruction, 23.79% ± 12.88% MVIC; postinstruction, 19.72% ± 13.92% MVIC; r = 0.80; P<.001).
Landing instruction produced both a statistically and clinically significant change in landing mechanics in persons post-ACLR. Conscious improvement of the absorptive power of the surgical limb was marked by decreased hamstring activity and cocontraction during single-limb landing.
测试前/测试后对照实验室研究。
确定前交叉韧带重建（ACLR）患者在单腿落地任务中，接受旨在改善膝关节屈曲的指导后，股四头肌和腘绳肌神经肌肉激活的变化。
临床医生建议接受ACLR的患者在落地任务中增加膝关节屈曲，以改善冲击衰减。此类指导背后的另一个长期理念是增加腘绳肌与股四头肌的共同收缩，以限制胫骨在股骨上的前向剪切力。本研究探讨了在落地时增加膝关节屈曲的指导后，膝关节肌肉的共同收缩是否发生变化。
34名单侧ACLR且身体活跃的受试者参加了一次测试。在接受增加膝关节屈曲并减少落地冲击的指导前后，分析手术侧单腿落地的动力学和运动学。使用表面肌电图分析股外侧肌和股二头肌的活动，并将其归一化为最大自主等长收缩（MVIC）。在落地的承重阶段对共同收缩指数进行积分。
接受指导后，膝关节屈曲峰值增加（指导前平均值±标准差，56°±11°；指导后，77°±12°；P<0.001），垂直地面反作用力峰值降低（指导前，3.50±0.42体重；指导后，3.06±0.44体重；P<0.001）。指导后共同收缩也降低（指导前，30.88%±17.68%MVIC；指导后，23.74%±15.39%MVIC；P<0.001）。共同收缩的变化与腘绳肌活动的降低相关（指导前，23.79%±12.88%MVIC；指导后，19.72%±13.92%MVIC；r = 0.80；P<0.001）。
落地指导在ACLR术后患者的落地力学方面产生了统计学和临床意义上的显著变化。手术侧肢体吸收能力的有意识改善表现为单腿落地时腘绳肌活动和共同收缩的降低。
