Abstract: By using the Dartfish motion analysis software, this paper made a sports biomechanical analysis of the'rabbit' camera-freeze pictures of backward pedaling and swing of Usain Bolt, Asafa Powell, John Blake, Morris Green, Fermi Ogunod and Su Bingtian during 100-m sprint. It is concluded that the motions of the swinging leg during back pedaling include: completing a small-range increase in the knee joint angle before the body, and then completing a large-range increase in the knee joint angle. The function of the swing change is to coordinate the extension and muscle strength of the rear pedal when the swinging leg completes a large-range increase in the angle of the knee joint, that is, the swinging leg swings in front of the body reaches 3/4 of the movement amplitude period, the pelvis completes large-scale "fan" horizontal rotation, which is commonly known as the key timing of "hip pushing". But the amplitude of back pedaling and thigh swinging in this period is not large, only the pelvis rotation, that is, the "hip-pushing" amplitude is the largest.

Key words: 100-metre sprint, backward pedaling, winging, pelvis rotation, timing