This debate will never settled because players of all levels will always have anecdotal opinions.
And even understanding the video is difficult. There is no doubt you can see forward flex on many, many forehands.
But huge numbers of them when you study at high frame rates flex very little around the contact, ie the wrist is laid back the same amount before during and after.
And you can actually find many examples where the contact actually pushes the wrist back.
Brian Gordon studies offer an explanation of the contradictions. The forward flex can contribute to racket speed, but the way the muscles work on a good forehand, this occurs through the forces generated by the larger muscles.
You can call it snap if you wish, but it is a consequence of other movements. And this is actually true on the serve as well.
Now on the forehand what confuses things even more is that the entire hitting arm and racket are also rotating from the shoulder joint. This causes the wrist along with everything else to turn over greater or less amounts depending on the windshiled wiper.
So everyone can claim to be right. If a player feels his wrist move and describes that as "snap" it's hard to argue with that. But players have proved notoriously inaccurate in giving biomechanical descriptions about how the body actually works--why would they care to when hitting the ball is essentially a matter of developing the right feel?
For me the bottom line is what are the positions? Understand it or not. Explain it accurately or not. Call it anything you like, believe you get there anyway you like, get there anyway you like--if the swing shapes are corresponding to the positions of great forehands hit from similar positions with similar intentions, that'll be good for your forehand.
The challenge is what approach helps players without world class natural gifts actually do this.
Last edited by JohnYandell; 12-01-2012 at 03:41 PM.