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

• Main Author: 范凱閎
• Other Authors: 游志雲
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/83406440653931605393

碩士 === 國立清華大學 === 工業工程與工程管理學系 === 102 === 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.