The purpose of this study was to clarify the lower extremity function in terms of the shock absorption during unsynchronized-foot landings. The characteristics of the supination and pronation in the ankle joint at landing were investigated, assuming that the measurements of the impact force on the body could be demonstrated by the changes that occurred during 3 different landing motions: —unsynchronized-foot landings, synchronized-foot landings, and one-foot landings. Subjects jumped to the floor from 10-cm footstools 3 times for each type of landing. For the synchronized-foot landing, the rear foot angle was 92.2° at the start of landing and did not change significantly from landing start to 100 msec. For the one-foot landing, rear foot angle was 95.1° at the start of landing and decreased rapidly to 87.1° by 75 msec, and then increased rapidly to 90.8° by 140 msec. For the unsynchronized-foot landing, the rear foot angle was 93.8° at the start of the landing, decreased rapidly to 88.0° by 75 msec, and then increased rapidly to 89.9° by 115 msec.
It was clarified that the lower extremity function for the shock attenuation during landing with the unsynchronized-foot was similar to that with one-foot landings, and the lower extremity function for supporting the body after another foot landing was similar to that after the synchronized-foot landings in this study.