The coach said I wouldn't tuck my knees when I stood in the long jump?

Judging from your situation, there are still some problems in the abdominal muscle strength of your standing long jump technique. The achievement of standing long jump depends on your skill, explosive power of lower limbs and abdominal muscles and your overall coordination ability. The standing long jump technique consists of four parts: pre-swing, take-off, flying and landing. Suggestion: 1. Master and improve your movement skills: Pre-swing: open your feet left and right, shoulder width apart, swing your arms back and forth, straighten your legs when swinging forward, bend your knees to lower your center of gravity when swinging backward, lean forward slightly, and swing your hands back as far as possible. Key points: coordination of upper and lower limbs. When swinging, the center of gravity is lowered by stretching and bending, and the upper body leans forward slightly. Take-off and take-off: push your feet to the ground quickly and forcefully, swing your arms slightly from back to front, jump forward and take off, and fully expand your body. Key points: the pedal should be fast and powerful, the leg pedal and the hand swing should be coordinated, and the aerial exhibition should be sufficient, emphasizing the instantaneous pedal action before the forefoot leaves the ground. Landing cushion: abdomen tuck, leg lift, calf stretch forward, arm swing back forcefully, knee bend and landing cushion. Key points: grasp the timing of calf extension, bend your legs forward, swing your arms backwards, and don't fall backwards after landing. 2. Strengthen the auxiliary exercises of standing long jump: bend your knees to take off in situ, do straight leg standing in the air, fully open your hip joint, do back bow action, and bend your knees to cushion when landing. Jumping forward with one leg: generally, the method of left (right) to right (left) is used to practice, and the distance is controlled at about 25-30 meters to complete 3-4 groups. Abdominal jump, frog jump, sit-ups exercises: take off from an upright position, bend your legs and knees in the air to touch your chest, and bend your knees to cushion when landing. This exercise is called abdominal jump. The continuous standing long jump can be called leapfrog. These exercises must be repeated, which is a very effective means to improve your abdominal muscle ability. Practice of crossing a certain height and distance or a certain distance and height. As long as your skills and abdominal muscle strength are enhanced, there will be no problem with your abdomen.