評估利用室內自行車阻抗裝置模擬戶外騎乘之可行性

Abstract

由於現行自行車研究常用測功機來取代室外實路騎乘實驗，但仍沒有證據顯示該方法可以達到好的室外騎乘重現效果，故本研究的目標為架設一個環境阻抗模擬裝置並評估取代室外自行車騎乘實驗的可行性，藉以提供後續以該裝置進行室外實驗模擬的合理性。本研究以可使用個人自行車的訓練台為基礎架設一環境阻抗模擬平台，利用煞車皮與直流馬達對自行車產生可控制之阻抗值，並藉由阻抗量測實驗對阻抗裝置的輸入電流與欲模擬的室外騎乘條件進行連結，以達到阻抗控制的效果。本研究募集五位無騎乘自行車障礙的成年人(非專業騎士)進行騎乘實驗，使用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之室外的自行車實驗平台，實驗條件為兩種坡度(柏油水平路面與五度上坡)與三種踩踏率(40, 60, 80 RPM)，再於室內以前述組抗模擬平台提供相近的阻抗值以同一自行車實驗平台進行室內騎乘，並以室內外騎乘時的踩踏力差異量的Mean Absolute Error(MAE)驗證該裝置是否達到模擬室外騎乘阻抗的效果。騎乘時也記錄六條下肢肌肉之表面肌電訊號(左腿股外側肌、股直肌、股內側肌、股二頭肌長頭、脛前肌及外側腓腸肌)，再根據Correlation及Root Mean Square Difference (RMSD)兩種分析方法得到室外自我重複性參數與室內外重現性參數進行比較。本研究先確認室外與模擬的踩踏力具有好的相關性(MAE<0.2；阻抗值誤差22%以內)，代表具有好的阻抗模擬能力。主要結果為：1.股外側肌、股直肌、股二頭肌、脛前肌及外側腓腸肌於室內外重現性(相關係數平均差異25%)有顯著優於室外騎乘的活化程度重複性閾值的情形(p<0.05)，少數肌肉(如股內側肌)在本研究之室內外重現性不足，無法證實適用於該裝置。2.在非極端的環境阻抗值下(46N~116N)，阻抗值較低的實驗條件具有較高之室內外重現性。結論為本研究架設的阻抗模擬裝置有模擬戶外騎乘下肢肌肉活化狀態的能力，並具有模擬室外實路騎乘的可行性。

Ergometers, instead of outdoor cycling, were often used for bicycle studies. However, previous studies have demonstrated differences existed between cycling on ergometers and outdoor real roads. The purpose of this study was to establish a simulator to simulate environmental resistance of outdoor cycling, and to evaluate the feasibility of using the developed environmental resistance simulator to replace outdoor cycling. The approaches were to first establish a resistance simulator with a brake and a DC motor, and develop an algorithm to correlate the input current to the DC motor with corresponding outdoor conditions. Five healthy (untrained) subjects were recruited for this study. Each subject performed cycling outdoors on real-roads, with 2 slopes (level asphalt and 8%-slope uphill asphalt road) and 3 different cadences (40RPM, 60RPM and 80RPM), on an instrumented bike, and similar simulated resistance conditions indoors on the same instrumented bike. Surface electromyography (EMG) signals were recorded from left vastus lateralis (VL), rectus femoris (RF), vastu medialis (VM), biceps femoris long head (BF), tibialis anterior (TA) and gastrocnemius lateralis (GL). Coefficients of correlation and root mean square differences (RMSD) were employed to examine the feasibility of using indoor cycling on the developed environmental resistance simulator to simulate outdoor real-road cycling. Low pedal force difference (Mean Absolute Error<0.2 and less than 22% resistance difference) between outdoor and indoor cycling demonstrated successful resistance simulation of our developed environmental resistance simulator. We found that most investigated muscles (VL, RF, BF, TA and GL) showed sufficient repeatability (significantly better than the statistical outliers of outdoor reproducibility under similar conditions) between indoor and outdoor cycling (with mean coefficients of correlation of 25%). We conclude that our developed indoor environmental resistance simulator could be used for simulating outdoor real-road cycling to induce similar lower-limb muscle activities.