改變踏車運動迴轉速與負荷量之下肢肌電學與踩踏力量分析

Abstract

目的：比較踏車運動中以不同踩踏頻率(60 rpm、75 rpm、90 rpm)，進行不同負荷強度之運動時(50% POV、65% POV、80% POV)，對於踩踏輸出力量與下肢作用肌之激發模式是否有所影響。方法：12名健康成年男性(平均年齡24.5 ± 0.9歲、身高174.3 ± 4.4公分、體重73 ± 8.4公斤)在實驗第一階段以漸增負荷法測得各受試者之踏車運動最大穩定輸出功率(POV max)，實驗第二階段以平衡次序法進行三種不同運動強度與三種踩踏速度之踏車運動測驗，並分別記錄九種實驗情境中踩踏力量與下肢肌電圖之變化。結果：不同運動測驗情境中，踩踏力量之負功隨著踩踏頻率的增加而上升，且踩踏作用力之作用趨勢提前達顯著差異。大腿作用肌活化率隨著踩踏頻率的增加而下降，而小腿則相反，隨踩踏頻率的增加而活化率上升。結論：若以踩踏效率為依據，未受訓練者較佳之踩踏迴轉頻率為60 rpm；同時踩踏作用力的趨勢會隨著踩踏頻率的增加而前移，亦會隨著踩踏頻率的增加使力量輸出曲線平滑化，且三種運動強度之結果相近；若以作用肌活化率為依據，大、小腿肌肉在踩踏過程間活化率呈現消長現象，無顯著趨勢；在踩踏力量的實驗中，踏板測力計之重量會影響原始資料的數值，且踩踏頻率越快變化越明顯。Purpose: The aim of this study was to compare the pedaling force and lower extremity EMG in different cycling intensity(50%、65%、80% POV) with different pedaling rate(60、75、90 rpm). Methods: Twelve healthy males(age 24.5 ± 0.9 yrs；height 174.3 ± 4.4 cm；weight 73 ± 8.4 kg) accepted power output at VO2 max(POV) tests by cycle ergometer in stage 1. In stage 2 these nine trial(3*3) were completed respectively by counter-balance design. During these tests, we recorded the pedaling force and lower extremity EMG by load cell(1000Hz) and EMG recorder(1000Hz). Result: In different trials, the negative pedaling work was increased when pedaling rate increased, and peak pedaling force was significantly different early in the cycle. The firing rate of thigh muscle decreased by increasing pedaling rate; on the contrary, the firing rate of thigh muscle increased by increasing pedaling rate. Conclusions: The optimum cadence is 60 rpm based on pedaling efficiency; furthermore, the tendency of pedaling force shifted forward and the curve of power output was smoothed when pedaling rate increasing. In accordance with muscle firing rate, the firing rate of thigh and leg muscle was negative correlated, but the tendency wasn’t significantly different. In the experiment of pedaling force, the weight of load cell affected the results, and as the pedaling rate increased, the effect was more obvious.