Lie on your side, straighten your upper body and feet, and lift up at the same time, stretching upward as far as possible, preferably 10- 15 seconds, at least 6-8 times.

Lie on your stomach, hold your ankles with your hands (your back will bow), and try to spread your arms and legs as far as possible, and do it for 6-8 times.

There is also: lean back, arch your body with your hands and feet on the ground, and try to keep it. But it's hard ...