This study analyzed the joint torque and the mechanical energy flow in the support legs of skilled male race walkers. Twelve race walkers were videotaped using a high‐speed camera at a frame rate of 250 Hz set perpendicular to the sagittal plane of motion; their ground reaction forces were measured with two force platforms. A two‐dimensional, 14‐segment, linked model was used to calculate the kinetics of the support leg joints. In the initial part of the support phase, the mechanical energy flowed into the thigh and shank by the torque of the large hip extensors and knee flexors. In the middle part, the mechanical energy generated by the torque of the large plantar flexors flowed to the foot and from the foot to the shank by the ankle joint force. The mechanical energy flow by the forward joint force of the support hip was significantly related to the walking speed in the final part of the support phase. Our findings suggest that race walkers in the final part of the support phase should exert the torque of the knee extensors and hip flexors to transfer the mechanical energy more effectively to the support thigh and shank.

This paper reviews a series of sport biomechanics research projects with long-term support of the Japan Association of Athletic Federations (JAAF) on the feedback loop of sport biomechanics. The JAAF supported these studies focusing on providing feedback to athletes and coaches based on biomechanical data. The primary topics of discussion are the standard motion model for teaching and coaching, inter-individual motion variation and deviation, and classification of athletes’ motions. Additionally, a comment is presented on motion-decision criterion, or objective function for body segment recruitment with examples of running and jumping. This paper concludes with remarks on how to expand the research in sport biomechanics and how to bridge the gap between researchers and practitioners. It is advisable for sport biomechanists to further explore biomechanical principles of human movement from the viewpoint of sports, to mutually understand features of research and practice sides and to be more involved in performance analysis and improvement in sports techniques.

The purpose of this study was to investigate the effects of fatigue on ground reaction forces and leg kinetics during all-out 600 m running. Eight male middle-distance runners were asked to perform two kinds of running, i.e. an all-out 600 m run and a non-fatigued 80 m run with the same velocity as at the 550 m mark of the 600 m run. Their running motion was videotaped and the ground reaction forces were measured at the 150 m and 550 m marks of the 600 m run and at the 50 m mark of the 80 m run. The step length, ground reaction forces, ankle plantar flexion torque, and knee extension torque of the support leg decreased due to fatigue. The hip joint torque of the recovery leg decreased due to the difference in running speed rather than fatigue. From these results, we suggest that in the final stage of 800 m race, a runner should not try to extend the step length by thrusting against the ground with the support leg but should maintain the step time as much as possible by moving the recovery leg quickly.