First, warm-up is not enough.

From us to the world champion, we should fully warm up. This can not only reduce the chance of physical injury, but also increase sports performance.

Second, the action is not standardized enough.

When doing it, the hand is about 30 cm from the shoulder. When your body is down, you can do about 90 degrees. Do not cross it. Otherwise, you will hurt your elbows and shoulders.

I hope my suggestion is helpful to you. o(∩_∩)o