1. Squat: When standing, your feet are hip width apart. When your knees bend and your body sinks, you can focus on your heels, so that you can apply weight to your thighs, which can effectively exercise your leg muscles and prevent your knees from being injured.

2. Jump and squat: Stand with your feet apart, hip breadth. When your knees bend and your body sinks, focus your weight on your heels, then quickly lift your weight and then squat down quickly.

3. lunge squat: when standing, step forward, step back, bend your legs at a 90-degree angle, and then slowly squat.

4. Side plate support: Lie on your side on the ground, keep your body in a straight line, and then support your body with one elbow and the other hand on your waist or side.