You can jump rope to warm up, and half of the ligaments should be slightly sweaty. Generally, pulling the waist requires people to cooperate with pulling the shoulders. If you bend over 90 degrees, you can hold the wall with your hands (someone can help you hold it, and it is best to help you). Just hold it with your arms. Keep your upper body still and press down.

Doing some chest expansion and stretching will also help, and most other movements need to be coordinated.