室外騎乘自行車阻力與功率輸出及肌肉活動情形之相互關係

Abstract

近年來，隨著自行車風潮的興起，自行車科學逐漸受到重視。本研究探討在固定踩踏頻率(60rpm)及騎乘姿勢(彎把姿勢)下，改變實驗的環境條件，利用室外實驗的數據進行分析，開發空氣與滾動阻力的估算公式。以及探討不同環境條件與踩踏時肌肉活動情形間之相互關係。藉此增加可模擬上坡及真實阻抗的室內自行車訓練台之開發潛力。為達上述目的，本研究將以自行車為基礎結合力規、編碼器、磁簧開關、肌電訊號量測系統以及生理訊號整合系統等儀器構築一室外的實驗平台，此平台可即時量測及紀錄騎乘時四條下肢肌肉之表面肌電訊號（股外側肌、股直肌、脛骨前肌以及外側腓腸肌）、踩踏頻率、騎乘速率、踏板力量以及與上述參數對應之曲柄角度。本研究募集10位無騎乘自行車障礙的成年人(非專業騎士)，平均年齡約為24歲。而在環境條件部份則包括平面柏油路、2度、5度以及平面的水泥地。最後本研究之結果在於發展了一套簡潔估算騎乘時環境阻抗之方法，有效將騎乘時室外的阻抗量化。而肌電訊號分析方面， 本研究利用室外實驗發現及驗證了幾個以往室內研究的結果：1.股外側肌之肌肉活化程度隨著坡度的上升而上升，也就是股外側肌為騎乘時動力提供之主要肌肉。 2. 脛骨前肌與外側腓腸肌，縱使固定踩踏率及姿勢等實驗條件，也會因受測者騎乘時的策略而產生不同的活化情形。 3. 當踩踏率固定時， 踩踏的扭矩增加與股直肌之間無顯著差異。

To advance our knowledge on real-road cycling, the objective of this study is to quantify drag and rolling resistance, and analyze muscle activity under different environmental conditions in outdoor cycling. The approach was to first establish an outdoor experimental platform (instrumented bike) to quantify biomechanical variables on real roads, and then examine the effect of slope and pavement on lower-extremity muscle activities during uphill cycling. The instrumented bike is a full-size bicycle equipped with an encoder, a load cell, a magnetic reed switch and multi-channel surface electromyography (EMG) sensors. The equipment can simultaneously measure and record EMG, pedaling cadence, cycling velocity, pedal force and crank angle in real-road environment. Ten healthy (untrained) subjects were recruited for this study. Each subject performed outdoor cycling, with constant pedaling cadence (60 rpm), under four randomly-ordered conditions: level asphalt ground, 4%-slope uphill asphalt road, 8%-slope uphill asphalt road, and level cement ground. Surface EMG signals were recorded from rectus femoris (RF), vastus lateralis (VL), gastrocnemius lateralis (GL) and tibialis anterior (TA) muscles to quantify the timing, duration, amplitude, and pattern of muscle activities during cycling in different conditions. After all, this study developed a simplified method for assessment of resistance forces in cycling and quantify environment resistance during cycling by regression analysis. According to the results of our outdoor study, we found: the muscle activation of VL increased with the slope and crank torque; high inter individual differences concerning the EMG patterns for GL, TA muscles; No statistical difference was found in the muscle activation of RF under different conditions.