Pronation: Wrist Action vs Forearm Rotation

By Jeff Counts (Hi-Tech Tennis) · Hi-Tech Tennis 240 FPS Optical Archive · Original Lesson ↗

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240 FPS Optical Kinematic Checkpoints

Camera & Framing

240 FPS High-Speed Shutter (1/2000s) · Side / 45° Oblique Plane

Kinematic Trigger

Sequential kinetic chain uncoiling from ground reaction to terminal impact

Angular Velocity

Internal shoulder rotation & forearm pronation peaking at contact plane

Jeff Counts (Hi-Tech Tennis) Analysis Note: Professional strokes maintain head and eye stability for 2–3 frames (approx. 12ms) through impact, ensuring absolute repeatability without compensatory wrist manipulation.

A key principle of top level strokes is what I call the "game of catch-up". You pull the racket, butt cap first, almost to the ball. This causes the racket to lag behind. Just before contact, the wrist and racket "catch up" to the rest of the arm, generating racket head speed.

For the serve, the wrist and racket not only "catch up" to the rest of the arm, but it also rotates into contact. So the wrist comes forward and turns/rotates into contact, generating tremendous racket head speed.

The angle between the racket and forearm go from 90 degrees to almost inline with the forearm. Not only does the wrist come forward, but the entire hand twists into contact so that the strings are flat with the ball. This forward torque causes tremendous racket head speed.