不同踏板傾斜角度對膝關節受力與下肢肌肉活化的影響

Abstract

近年來隨著自行車騎乘者增加，相關運動傷害之發生率也隨之上升，其中，髕骨股骨疼痛症候群(Patellofemoral syndrome)為最普遍之過度往復運動(Overuse injury)所造成的膝關節運動傷害，然而，先前自行車相關文獻是以膝關節往內側力矩(Valgus moment)與外側力矩(Varus moment)、或是股四頭肌出力不平衡(Quadriceps imbalance)作為髕骨股骨關節疼痛之可能原因進行探討。此外，踏板為自行車重要幾何參數之一，雖常為復健時建議可調整之方向，但仍未有明確之調整標準，須由多次調整試驗後才能確定最佳踏板方位。因此，本研究之目的為建立個人化自行車踏板傾斜角度調整之流程，以降低髕骨股骨關節受力為目標，利用肌肉骨骼模擬軟體搭配髕骨自由體圖(Free-body diagram of the patella)，計算不同踏板傾斜角度對髕骨股骨關節受力、膝關節各方向受力與力矩以及肌肉活化之影響，並針對個別受測者之肌肉骨骼模型進行探討。本研究以自行建構之室外自行車參數量測平台紀錄騎乘時的踩踏力、曲柄角度與下肢表面肌電訊號(Surface electromyography, surface EMG)，利用肌肉骨骼模擬系統(AnyBody Modeling System)模擬實際室外騎乘，並建立一模型驗證方法，利用肌肉活化期間驗證肌肉骨骼模型之準確性。由經所開發方法確認合理之個別化肌肉骨骼模擬，發現三位受測者之在踏板外翻(Eversion)下騎乘，膝關節往外側力矩(Varus moment)與往內旋轉力矩(Internal axial moment)的峰值皆較踏板水平時降低。本研究更進一步結合運用髕骨自由體圖，發現將踏板外翻10°可使三位受測者之髕骨股骨關節受力較踏板水平時降低2%，因此，更能夠支持踏板外翻確實可降低本研究受測者運動傷害的發生風險。此外，本研究之流程也可用於復健或訓練方面，以踩踏實驗與人體肢段參數量測建立個別肌肉骨骼模型，利用模擬提供個別受測者適合的踏板角度建議。

With the popularity of the cycling activity, the related injuries are becoming more common. Overuse injuries in cycling are usually manifest at the knee joint, and the patellofemoral syndrome is the most common caused. The knee moment components (varus/valgus moment) are thought to be primarily responsible for the etiology of patellofemoral syndrome because of their relationship to muscular imbalances. Although some interventions has been used, such as adjusting the pedal angle, for reducing cycling injuries, no standardized procedure for the adjustment. Therefore, the purpose of this study was to establish a procedure to generate individualized musculoskeletal model for real-road cycling simulation and pedal orientation adjustment, for reducing patellofemoral joint force. The developed model allow us to individually observe the effect of the pedal orientations on the patellofemoral joint force, knee joint forces and moments, and lower-limb muscle activities. We used a custom-made outdoor experimental bike platform to first measure the pedal force, crank angle and surface electromyography (surface EMG) signals simultaneously during outdoor real-road cycling. A subject specific three-dimansional musculoskeletal model was then built using AnyBody modeling system. The model was validated with a newly developed validation method comparing the muscle activation between simulated and outdoor experiments. We found that when the foot/pedal was everted, varus knee moment and the internal axial moment decreased as compared with the neutral condition. Combining the musculoskeletal simulation with a free-body diagram/model of the patella from a previous study, we further found that the reduction of the patellofemoral joint force was 2% with the everted foot/pedal during cycling. The developed procedure could be used for rehabilitation or training, to provide subject-specific advice on pedal orientations and cycling parameters.