The Proverbial Cannon.

TOPSPIN
THE WRIST... ROLLOVER... PRONATION

Spin is simply a matter of the strings brushing against the ball. For topspin the racket face brushes up because you're swinging low to high.

The controversy centers around the use, or non-use, of the wrist. Is the wrist in a fixed position for both backswing and forward swing, or does it move? Does the rollover action contribute to topspin, is pronation involved?

The status quo always cops out by saying pro A hits the ball a ton because he does use his wrist/rolls over/pronates but that you shouldn't. ... keep the arm and wrist fixed throughout backswing and forward swing to "minimize every possible chance for error." Condescending, isn't it.

PRONATION

..believe in you, in your human body.

The "use of the wrist" back then is what we call pronation today. The establishment didn't grasp it then, and still doesn't now. It's not wrist, it's pronation. Hallelujah.

Pronation means rotating the hand or forearm counter clockwise, so the palm faces forward, then downward, or, in the extreme, back.

Pronation is just a fancy word for rolling the hand and forearm into the ball when you hit it. In most pros with rocket forehands, like Tommy Haas here, the racket face rolls over, creating a unique after-effect.

...your job is to keep your racket face vertically against the ball as you brush up low to high. How can you do this when the ball's tweaking the racket face? You can plan to apply a counter force.

Pronation applies an active counter force to prevent the racket face from tweaking at contact.

Adding wrist flexibility and pronation with an arm that is flexible throughout the swing creates the proverbial cannon.

Lay the wrist back to start, keep it strong and vow not to flop it, and you'll naturally access it during the motion. ... you'll hit the ball out in the beginning, that's expected, like what happened when you first hit the gas pedal on a car. But you can handle it. And pronation? Just simply roll the racket or the hand into the ball on the forward upward swing, that's all. Counter the ball, don't ever try to keep the wrist or arm fixed.