不同騎乘姿勢對自行車踩踏力量之影響

The Effect of Different Riding Postures on Pedaling Force

前言：自行車運動中的坐墊高度、握把高度之設定不同，會改變使用者的騎乘姿勢，進而對運表現產生影響。常見在比賽中途或一般騎乘者在面臨衝刺、爬坡等高負荷騎乘時，會將身體軀幹向前俯臥騎乘，此點除了減低風阻的因素外，先前研究卻指出採用俯臥騎姿會較前傾騎姿消耗更多能量，提前使闊背肌疲勞等情形。而本研究之目的即為比較俯臥騎姿與前傾騎姿對於自行車運動中踩踏輸出功率的影響。方法：研究實驗中共有12名健康大專男性參與者，身高175.0±2.6cm、體重71.9±7.0kg、年齡24.2±1.6yrs。實驗中將六軸向測力器裝置於飛輪健身車左側踏板，以擷取使用者騎乘過程中的踩踏力量資料。共進行俯臥騎姿與前傾騎姿兩種實驗情境，分析使用者採用不同騎姿時的垂直踩踏力量與前後踩踏分力，以及力量分佈趨勢。結果：實驗發現採用俯臥騎姿的垂直踩踏力量達0.19BW，大於前傾騎姿的0.13BW，增加了46%。踩踏前後分力方面俯臥騎姿也較前傾騎姿高出28%，且力量峰值皆提早發生。討論：探討踩踏力量增加的原因為採用俯臥騎姿時，身體重心較前傾騎姿前移，因此體重向前分配，形成採用俯臥騎姿時坐墊所受重量減少而握把及踏板處所受的重量增加，因此增加了踩踏力量。且使用俯臥騎姿時，延展了股二頭肌、半腱肌、半膜肌等肌群的收縮前長度，因此使踩踏過程中的肌肉收縮力量更大，也是增加踩踏力量的原因之一。

Background: In cycling， the setup of seat and handlebar will change user’s trunk position andaffect rider’s performance. Generally， the competitive cyclists or normal users will choose dropposition when they confront high intensity cycling as sprint or uphill to reduce air resistance. Butaccording to previous research， the drop position on in cycling will also increase energyconsumption and accelerate fatigue compared with the top position. The purpose of this study wasto compare the pedal power output between the drop position and top position during cycling.Twelve male normal riders (height 175.0±2.6 cm， body mass 71.9±7.0 kg) were recruited in thestudy. A 6 axis load cell was set at left pedal of flywheel fitness bike to capture the subjects verticaland horizontal pedaling force data in drop position (DP) and top position (TP) for analyzing riders’vertical pedaling power， the component of pedaling forces front and rear， and force distributiontendency. Results: The results showed that the vertical pedaling force in DP attained 0.19 timesmean body mass greater than TB’s 0.13 times mean body mass with 46% increase. Moreover， theDP was also 28% greater than TP in the component of pedaling forces front and rear and the peakpedaling force also appeared earlier in DP than in TP. Discussion: The DP having more pedalingforce increase was due to the subjects’ center of mass shifting more forward in DP than in TP，therefore the body weight was distributed over handlebar and pedals leading to the reduce of seatload and the increase of pedal load; as a result， the pedaling force increased. The other reason wasthat the length of bi-articular muscles were extended when taking DP leading to a stronger musclecontraction force during pedaling and resulting in greater pedaling force. Conclusions: In cycling，the pedaling force in DP was indeed greater than in TP.