Yasushi Enomoto

Athletics: Joint torque and mechanical energy flow in the support legs of skilled race walkers

Abstract 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 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.

Effects of work-matched supramaximal intermittent vs. submaximal constant-workload warm-up on all-out effort power output at the end of 2 minutes of maximal cycling

Abstract We tested the hypothesis that work-matched supramaximal intermittent warm-up improves final-sprint power output to a greater degree than submaximal constant-intensity warm-up during the last 30 s of a 120-s supramaximal exercise simulating the final sprint during sports events lasting approximately 2 min. Ten male middle-distance runners performed a 120-s supramaximal cycling exercise consisting of 90 s of constant-workload cycling at a workload corresponding to 110% maximal oxygen uptake (VO2max) followed by 30 s of maximal-effort cycling. This exercise was preceded by 1) no warm-up (Control), 2) a constant-workload cycling warm-up at a workload of 60%VO2max for 6 min and 40 s, or 3) a supramaximal intermittent cycling warm-up for 6 min and 40 s consisting of 5 sets of 65 s of cycling at a workload of 46%VO2max + 15 s of supramaximal cycling at a workload of 120%VO2max. By design, total work was matched between the two warm-up conditions. Supramaximal intermittent and submaximal constant-workload warm-ups similarly increased 5-s peak (590 ± 191 vs. 604 ± 215W, P = 0.41) and 30-s mean (495 ± 137 vs. 503 ± 154W, P = 0.48) power output during the final 30-s maximal-effort cycling as compared to the no warm-up condition (5-s peak: 471 ± 165W; 30-s mean: 398 ± 117W). VO2 during the 120-s supramaximal cycling was similarly increased by the two warm-ups as compared to no-warm up (P ≤ 0.05). These findings show that work-matched supramaximal intermittent and submaximal constant-workload warm-ups improve final sprint (∼30 s) performance to similar extents during the late stage of a 120-s supramaximal exercise bout.