We examined the influence of the mechanical work done by the lower limb joints and segment rotations on the mechanical energy of the center of mass (E_CoM) during three take-off phases in the short approach triple jump. A motion capture system and three force platforms were used to collect the three-dimensional markers and ground reaction forces during the three take-off phases from eight male triple jumpers. E_CoM decreased during the step and jump phases, whereas E_CoM increased during the hop phase. The change in E_CoM during the jump phase was significantly correlated with the net mechanical work done by the knee joint torque. The increase in the vertical component of E_CoM due to the stance leg thigh rotation during the step and jump phases was significantly lower than the hop phase. The knee joint torque contributed to the mechanical energy inflow on the stance leg thigh, and it led to an increase in the vertical component of E_CoM. These findings imply that triple jumpers are required greater lower limb joint torque production, especially knee joint torque, to produce thigh rotation and maintain the mechanical energy which was obtained during the approach sprint.

To prevent chronic ankle instability (CAI) and understand why outcomes vary among patients with a lateral ankle sprain, it is important to examine the differences in movement patterns between copers without recurrent ankle sprain and those who develop CAI. The differences in coordination between both groups are unclear, even though abnormal movements of the rearfoot may affect the forefoot through coupling. Therefore, the purpose of this study was to investigate the coordination between the rearfoot and forefoot of CAI, coper groups. Twelve individuals with CAI, 12 copers, and 12 controls ran on a treadmill at a fixed speed of 2.5 m/s. Kinematic data of the rearfoot and forefoot were measured using a three-dimensional motion analysis system. The coupling angle between the rearfoot and forefoot was calculated using the modified vector coding technique and was classified into four coordination patterns. During early stance, the coper group showed a significantly greater proportion of anti-phase with distal dominancy than the CAI group (p<0.05), and in-phase with distal dominancy approached to decrease than the CAI group (p=0.052). During midstance, the CAI group approached to increase proportion of anti-phase with distal dominancy than the control group (p=0.053). During late stance, the coper group showed a significantly decreased proportion of anti-phase with distal dominancy than the control group (p<0.05). This study may provide in-depth knowledge of motor-behavioral characteristics of coper and CAI.