Originally Posted by toly
I analyzed Federer inside out hard FH on the APAS System http://www.youtube.com/watch?v=pPLmCqGIotM
There are data about his arm speed and acceleration around the wrist during forward swing.
The picture demonstrates that Federer is able to increase acceleration/force of the arm from frame #1 to #9. The magnitude of the force declined after frame #9. Around impact, frame #24, acceleration decreased more than 70%.
So, he is not able to accelerate the arm significantly near impact. But, this is very hard FH and without doubt he is trying to produce maximum acceleration/force.
Question: What is wrong with Federer?
The answer will be tomorrow.
Acceleration will obviously decrease as he is swinging up into the ball, compared to swinging down with gravity. So what? Whatever force he is exerting needs to counteract gravity, so he cannot keep on increasing the force. What counts is the momentum already built up leading to collision.