How to touch the ball = if a slow loop, with maximum friction; if a fast loop, with mixed friction and force contact
When to touch the ball = for maximum topspin, as the ball is descending; for fast topspin, at the top of the bounce
Where to touch the ball = if a slow loop, toward the bottom of the ball; if a fast loop, slightly below the center of the ball
When playing topspin strokes, you can contact the ball at several points along its path to produce varying amounts of spin and speed. For maximum spin, contact the ball as it descends. For fast topspin, play the ball at the top of the bounce.