The paper analyses the impact of ligament stretch and tension on the speed of movement in martial arts from the perspective of sports physiology. It establishes the numerical relationship between the peak impact value of the ligament speed and the differential equation of the flexibility of the joints in the initial stage of tension (impact peak). It was found that the differential equation of the ligament tension of the movement is formed after the movement is stable, which cannot reflect the flexibility of the ligament and the mastery of the movement. In this paper, a tension calculation model for ligament equilibrium is established by using a kinetic method of motion. Although it is a static equation, continuous use can obtain dynamic effects. The simulation proves that the initial tension change is more realistic.