In fact, hula hoop is very useful, just stick to it every day. Squeeze your meat more when you are free. Do stretching exercises.
As for the arm, I just succeeded in the experiment. I share it with you as follows:
1. Feet are shoulder width apart.
2. Put your hands behind your back, hook two thumbs and open your other fingers.
3. Lean forward vigorously and lift your chin at the same time, then lift the arm behind you forcibly, keep swallowing posture 10 seconds and then return to the original posture.
Do a group every morning and evening, 20 times in each group.
The effect of persistence is very good, especially during menstruation, and the effect is the best.
I learned this from a book, and it really works. You should do it properly and insist on it. Actually, it's not difficult at all.
Reference: girlfriend magazine.