What Pronation Looks Like: Frame-by-Frame

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.

I would like to look at "pronation" much more closely. It is the key to a big serve, and it is the heart of a big overhead as well, so I think it will be very worthwhile to explore pronation in depth.

There is a very specific sequence of events that occurs just before impact. First, you can see how the racket and forearm are at a 90 degree angle in the first frame. This comes from "pulling" the racket, butt cap first, upward. In this first frame, the wrist is laid back, causing the racket to be in the "Big L" position.

Now the wrist will "catch up" to the forearm by whipping forward and turning (rotating) into the ball. On impact, the wrist will remain stable (it has caught up to the rest of the forearm) and the entire arm will turn outward.

Federer's technique is identical to Johannson's. The racket twists into contact and then the entire arm turns outward after impact. Notice the long extension of the arm and racket towards the net.