The explosive force of punching and kicking can be produced by using the force generated by waist rotation. Take the straight fist as an example. When the reaction force generated by pedaling is transmitted to the hip joint along the ankle-knee joint, the rotation of the hip joint accelerates the force to rotate in plane at the hip joint, and accelerates again with the coordinated movement of the waist muscles. When transmitted to the upper body, the strength of the back muscles will be combined and transmitted to the shoulders, the shaking of the shoulder joint, the extension of the elbow joint and the release of the wrist force, so that the strength of the straight fist will be brought into full play. If you master the skills of waist and hip joint force, the upper body strength and leg strength will be integrated, while ignoring or not knowing the role of waist can only be local force and scattered force.