Ha ha. It's normal for him to have a shoulder injury when he just started practicing windmill. Let him straighten his legs as much as possible and pay attention to the type of strength movements when doing it.

Then practice the first lap more. When you are proficient in the first lap, the next lap will be very simple, and the foundation will be laid in front.

Zhou Yang 12:23:36

I haven't found that point yet, so it's normal to fall, because I don't have enough inertia to go down naturally, and my shoulder hurts because there is no horizontal line, which will naturally rub. When my feet are not straight and there is no horizontal line to go down, my knees touch the ground. Grasp the essentials and practice more. Practice makes perfect.

I asked them when I saw your question. That is our Changde boy. I hope it helps you. Come on! Gai Juk Tiu Mo