Lie on your back and bend your knees with one leg. The step of muscle stretching exercise is to lie on your back, bend your knee slightly with one leg, pull the knee of the other leg to your chest, and then slowly straighten your raised foot carefully. The muscle groups are as follows: The main muscle groups are hemimembranous muscle, semitendinosus muscle and biceps femoris. The trick is that the key point of this lacing action is that the toes are up. If the toes face sideways, it will cause uneven stress on the muscles at the back of the leg, which will cause muscle imbalance in the long run. Straighten out one leg. Put the other leg on the knee of the straight leg and push your hips to the ground. The main muscle groups are tensor fascia lata, gluteus medius and gluteus minimus. The strength of lacing exercise can be adjusted by the degree of pushing down the cross and the straightness of the trunk.