Small sample study in wrist shift and thumb use during level 3 bar skills.
Click PLAY or watch it on YouTube.
Personally I don’t like to much mention grip change and thumb position to gymnasts. Instead, I do specific drills to improve the grip change. Double back hip circle for female beginners. Various sole circle series, both forward & backward.
Don’t be too dogmatic on wrists and thumbs. It’s not critical.
Safest is for girls to keep their thumbs around or partly around in support, with the fingers or half way around during swing.
Look at what’s really happening on Porgras’ Stalder 1 1/2 to Jaeger.
That .gif was linked by paksalto.
Gymnastics Coaching.com 