Originally Posted by toly
When we rotate trunk with acceleration, IMO the passive arm will never whip around the body. Thus, the arm and its parts should be active, or we should slow down trunk acceleration. Does it make any sense?
If trunk doesn’t rotate at all, the arm by itself still can rotate around shoulder joint etc. I believe that good athlete can hit 100 mph FH without trunk rotation, by using just active arm motions. He will never be able to do that with passive arm relying on whip effect. I tried it many times and always got pathetic FH.
My experience, pretty much. But all those exercises helped me to improve my body positioning, posture, core and back muscles etc.
Now I simply add arm/wrist/fingers action to turn racquet head around, once I got fundamentals (lower/upper body) right.
It is simple physics: during body rotation centrifugal forces pull racquet forward/away, not around the body. There is no physical way racquet shaft will bump against your left shoulder on follow through if your hitting arm is all passive during upper body rotation.