公路自行車最大踩踏功率的騎乘姿勢研究

The Investigation of Riding Posture with Maximal Pedaling Power on Road Bikes

范凱閎

指導教授 ： 游志雲

國立清華大學/工學院/工業工程與工程管理學系/碩士(2014年)

https://doi.org/10.6843/NTHU.2014.00280

摘要

本研究目的在於探討公路自行車在最大踩踏功率下的騎乘姿勢，研究結果可作為車架設計與產品選購的參考。最大踩踏功率的騎乘姿勢 (名之為最佳騎乘姿勢，optimal riding posture)的人因工程，已經成為自行車騎乘者關注的議題。例如，為何騎乘者都要將上身極度壓低呢？大多數的人都不假思索地回答:降低風阻！殊不知，另外的目的(可能更主要)，是藉由壓低上身來壓縮大腿-與-上身的角度(torso-to-thigh angle)，以利提升踩踏力量!這是個人因工程的推論，值得探討。
本研究分別量測在3個上身立式(erect)與2個仰式(supine)姿勢下，126個踩踏位置的靜態最大踩踏力量，搜尋最佳騎乘姿勢。3個立式的上身角度分別為0°、45°、90°；2個仰式角度為135°、180°(卡式座標角度)。這126個踩踏位置是足球可以觸及的範圍，為一個9 x 14的二維矩陣，格距為5公分。測量平台的主要元件為一個200kg的荷重元（load cell），可以調整126個踩踏位置。本實驗的受測者為5名健康男性大學生，他們接受適當酬勞參與本實驗。
本研究結果分為「最大踩踏力量」、「最佳踩踏姿勢」二部分。最大踩踏力量的結果顯示，仰式135°姿勢下，各受測者的最大踩踏力量為5個上身姿勢中最高，且2個仰式的最大踩踏力量皆大於3個立式。在3個立式姿勢下，則以立式45°為最大，且最大踩踏力量與其體重幾乎相同；最大踩踏力量與上身角度呈現二次曲線，中間高而兩端低。仰式135°的最大踩踏力量為體重的107%，也就是高出立式45°約7%。與各別受測者呈現的結果相似，全部受測者的平均值也呈現相同的結果。
其二，「最佳騎乘姿勢」部分，就5位受測者在3個立式的上身角度來看，當上身為90°時的髖足連桿(髖關節至足球連桿)角度為29.18°(SD = 1.99°)，45°時為27.38°(SD = 1.54°)，在0°時為22.8°(SD = 1.34°)。ANOVA分析顯示5位受測者在5種上身姿勢下，最佳騎乘姿勢(髖足連桿角度)皆沒有顯著差異，亦表示不同體型的人是有相同的機能姿勢。至於各個受測者的髖足連桿長度與腿長比例，90°與45°約為80%，十分相似，沒有顯著差異；然者，0°為72%，顯著縮小。當上身姿勢逐漸由90°下壓至45°時，髖足連桿角度些微變小；然而由45°下壓至0°時，髖足連桿角度顯著變小。這個現象可以利用生物力學加以解釋，上身下壓導致上身-與-大腿夾角變小，因而帶動骨盆迴轉，並進而影響相關肌肉的長度與其最大自主收縮力量的位置，因此最佳騎乘姿勢的位置亦會受到影響。
驗證實驗結果，以本研究45°結果與過去相關研究做比較，過去公路自行車相關研究結果顯示座管角度72°與座墊高建議值(髖關節至下死點)為109 %胯下高，本研究計算結果則為座管角度73.3°和座墊高度建議值為103%。
總結研究結果，仰式的騎乘效率大於立式；上身夾角影響著最佳騎乘姿勢的位置；然而以3個立式部分，最佳騎乘姿勢為立式45°；在座管73.3°與座墊高度建議值103%的設計下，公路自行車騎乘者可呈現最佳騎乘姿勢，上述結果可作為建立車架設計與產品選購的參考數據。

關鍵字

自行車適配 ； 自行車人機介面 ； 自行車踩踏力量 ； 自行車功率輸出 ； 自行車人因工程 ； 自行車設計

並列摘要

The purpose of this study is to investigate the riding posture with maximal pedaling power on road bikes, and the posture will be a useful reference for the design and a sales guide for select and adjustment. The ergonomics of optimal riding posture and power output is becoming a leading concern of the road bikes users. Why a road bike rider is normally bending his torso downward significantly? It is inferred that other than the apparent reason of reducing air drag, the posture is to pose a small torso-to-thigh angle to maximize pedaling power. This hiding reason of the riding posture should be investigated.
An experiment was devised to measure the peak static pedaling forces at 126 positions while the torso is assuming in three erect and two supine postures. The 126 positions is a metric of 9 distances x 14 heights which are accessible by the foot ball. The 3 torso erect postures are torso erect 90°, torso erect 45°, and torso erect 0°; and 2 supine are torso supine 180°, torso supine 135°(angle in standard Cartesian).A measurement platform with a 200 kg load cell was fabricated for force measurement. Five healthy young males were paid and recruited as subject for participation.
The results are classified in 3 items: maximal pedaling force, optimal riding posture, and the relationship between optimal riding posture and maximal pedaling force. For the maximal pedaling force, the result show that for each individual, the greatest pedaling force is symmetrically appears in torso supine 135°; and the peak forces in two supine positions are all greater than the 3 erect ones. The greatest pedaling force among 3 erect postures appears in torso erect 45°symmetrically. These forces are all equal to their body weight, and all about 10% lower than that of the torso supine 135°. The result suggests that the peak force in relation to torso angle is quadratic. The pooled means of these maximal forces also exhibit similar phenomenon.
Secondly, for each of the 3 erect postures, the angle of the link of hip-and-foot ball are 29.38°(SD = 1.99°) for erect 90°, 27.18°(SD = 1.54°) for erect 45°, and 22.8°(SD = 1.34°)for erect 0°, and no difference among 5 subjects, but the link lengths are proportional to their leg length. Likewise, similar results exhibit for the 2 supine postures.
Finally, it is also interested to find the angle of the hip-foot ball link decreases as torso angle decreased. This phenomenon could be explained as the torso-to-thigh affect the rotation of pelvis which in turn alters the lengths of related muscle, thus the position of peak force changes.
The optimal riding posture of erect 45° is finally compared with previous study. Previous study showed that central bar angle is 72° and the sitting height (low dead point to the hip) is 109 % of leg length for road bikes. The calculated central bar angle of this study is 73.3°, and the calculated sitting height of this study is 103%.
The results of this study are quite promising which answered many enigmas: The supine is more effective in pedaling than the erect. The position of peak force is related to torso angle, for the erect the optimal riding posture is near 45°. The 73.3° central bar angle and 103% sitting height are also related to optimal riding posture. The results can be a useful reference for the design and a sales guide for select and adjustment.

並列關鍵字

bicycle pedaling force ； bicycling power output ； bicycling ergonomics ； bicycle design ； bicycle fitting

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