Measurement and Simulation of Biarticular Muscle Function During Human Walking

描述(申请人提供)：本研究的目的是测量和模拟双关节肌肉在人类行走过程中的功能。运动障碍的临床治疗通常包括对双关节肌肉进行有针对性的手术和康复干预。然而，要事先预测不同的治疗方法将如何改变一个人的步态可能是极具挑战性的。肌肉骨骼系统的计算模型提供了一种系统的方法来预测肌肉如何驱动运动。以前已经证明，模型预测往往是非直观的，有时与当前治疗策略所依据的假设不一致。然而，模型预测的准确性尚未确定，这限制了模型对治疗的影响。在这项研究中，研究人员使用电刺激实验来直接测量两块双关节肌肉--股直肌和腿筋--在行走过程中的生物力学功能。这些肌肉的异常激活通常是导致步态异常的原因，步态异常的特征是在行走的摆动阶段膝关节屈曲减弱，和/或在站立阶段膝关节过度屈曲。在实验中，受试者在仪表化的分裂带跑步机上以恒定的速度行走。在随机步态周期的特定阶段，然后使用电肌肉刺激来改变股直肌或腿筋的正常激活。使用运动分析系统记录对行走运动学的由此产生的扰动。比较无扰动行走和扰动行走，为评价个体肌肉的运动提供了依据。这些数据被用来检验这样的假设：站立时股直肌过度激活会导致摆动时肢体更加伸展，而摆动时腿筋过度激活会导致站立时肢体更加弯曲。将测量结果与计算模型预测进行比较，以便严格评估有关肌肉骨骼几何形状和肌力传递路径的假设的准确性。这项研究的预期结果是增强了对行走过程中双关节肌肉功能的理解，并提高了使用计算模型评估运动障碍的手术和康复治疗的信心。公共卫生相关性：运动障碍在患有神经疾病(如脑瘫)的个体中很常见。异常的运动模式会大大增加步行的代谢成本，并导致长期的关节退化和身体残疾。出于这个原因，手术和/或康复治疗经常被用来尝试纠正异常步态模式。然而，预测不同的治疗方案将如何影响患者的步态可能是具有挑战性的。本研究利用实验和计算技术评估肌肉在行走过程中的正常功能，从而为建立有效的干预措施提供科学依据。

DESCRIPTION (provided by applicant): The objective of this research is to measure and simulate the function of biarticular muscles during human walking. The clinical treatment of locomotor impairments often includes targeted surgical and rehabilitative interventions performed on biarticular muscles. However, it can be extremely challenging to predict a priori how different treatments will alter an individual's gait. Computational models of the musculoskeletal system provide a systematic way of predicting how muscles actuate movement. It has previously been shown that model predictions are often non-intuitive, and sometimes inconsistent with assumptions that underlie current treatment strategies. However, the accuracy of the model predictions has not been established, which limits the impact of the models on treatment. The investigators in this study use electrical stimulation experiments to directly measure how two biarticular muscles, the rectus femoris and hamstrings, biomechanically function during walking. Abnormal activation of these muscles is often implicated as a cause of gait abnormalities that are characterized by diminished knee flexion during the swing phase of walking, and/or excessive knee flexion during the stance phase. In the experiments, subjects walk at a constant speed on an instrumented, split-belt treadmill. At select phases of a random gait cycle, electrical muscle stimulation is then used to alter the normal activation of the rectus femoris or hamstrings. The resulting perturbations to walking kinematics are recorded using a motion analysis system. Comparison of un-perturbed and perturbed walking provides a basis of assessing the movement induced by the individual muscles. The data are used to test the hypotheses that over-activation of the rectus femoris during stance induces a more extended limb during swing, while over-activation of the hamstrings during swing induces a more flexed limb during stance. Measurements are compared to computational model predictions, so as to rigorously evaluate the accuracy of assumptions regarding musculoskeletal geometry and muscle force transmission paths. The anticipated outcomes of this study are an enhanced understanding of biarticular muscle function during walking, and improved confidence in the use of computational models to evaluate surgical and rehabilitative treatments of locomotor impairments. PUBLIC HEALTH RELEVANCE: Locomotion impairments are common among individuals with neurological disorders such as cerebral palsy. Abnormal movement patterns can greatly increase the metabolic cost of walking and contribute to long-term joint degeneration and physical disability. For this reason, surgical and/or rehabilitative treatments are often used to try to correct abnormal gait patterns. However, it can be challenging to predict how different treatment options will affect a patient's gait. This study uses experimental and computational techniques to assess how muscles function normally during walking, so as to contribute to a scientific basis for establishing effective interventions.