Exploring the possibilities for increasing maximum power output in human-powered vehicles

This paper investigates the potential for increasing the maximum power output of human-powered vehicles (HPVs) from the perspective of the generation and support structure of reaction forces against leg output. Conventional bicycle research has primarily focused on vehicles compliant with Union Cycliste Internationale (UCI) regulations, emphasizing lower-limb biomechanics, cadence optimization, and aerodynamic performance. However, the maximum power that the human body can produce is closely related not only to the lower limbs but also to reaction forces generated by the whole body, including the upper limbs and trunk. In this study, a non-UCI-compliant vehicle is examined, and a design hypothesis is proposed in which a Scrum Position, inspired by the rugby scrum posture, is introduced into the bicycle structure. By increasing the reaction-force support capacity that constrains leg force, this configuration enables the extraction of greater driving torque. Through the design and testing of a prototype vehicle, including riding experiments and static torque measurements, the study demonstrates the potential to achieve an average increase of 52.6% in static driving torque compared with the standing pedaling posture on UCI-compliant bicycles, which has traditionally been regarded as the maximum power-output posture. This paper does not aim to determine absolute performance values; rather, it presents a proof-of-concept study indicating that an unexplored degree of design freedom—namely, the design of reaction forces—exists in HPV design. The findings suggest potential applicability not only to non-UCI vehicles but also to other human-powered systems that require sustained high power output, such as human-powered aircraft and human-powered watercraft. This document is released as a pre-peer-review manuscript. Copyright is retained by the author. Unauthorized reproduction, redistribution, or modification is prohibited.