Abdominal muscle training: Lie on your back and straighten your legs. You can ask others to help you hold your feet. When you get up, your back is about 55 degrees off the ground, and when you fall back, your back will not work.
Landing completely, a little distance from the ground.
Back muscle training: prone, straighten your legs. (It's the same as the previous supine training, except that you must be straight when you get up. Cross your fingers and hold your head. )
The above training should be done in at least three groups every day, with 20 in each group, which can be increased in turn according to your own situation.
When the muscles are most sore, you must stick to it. If you don't persist, there will be no effect.
When you take the front axle and the rear axle, you are soft, and your waist collapses because your waist strength is not enough. So you can't control your body and angle as long as you do skills.
Also, walk more. It can strengthen the strength of hands and waist, and the angle problem will be improved.
These are all summed up by my own experience, I hope to help you.