Your tennis serve, measured from toss to contact.

How high your tossing arm reaches at its peak — read from your arm, not the ball. A long, tall toss arm is the platform the serve stands on.

Whether your tossing arm stays long at the trophy. A straight arm tosses with the shoulder, and that’s what makes the toss repeat.

The time from your tossing arm’s full reach up to the hit. Enough for a real trophy, not so much that you’re waiting under a moonball. This window is self-calibrated and stays that way: the published serve durations start their clock at the ball leaving the hand, which is earlier than our start, and the same studies find the serve's timing barely moves with skill — 0.92 s against 0.94 s between a 155 km/h group and a 130 km/h one. A rushed or stalled rhythm is worth naming; your time here is not a measure of how good the serve is.

The bend in your hitting arm at the trophy. Around a right angle stores the throw; a straight arm at this checkpoint has nothing left to release. Checked against the one study that splits professionals by ranking and left where it was: top-40 WTA players hold 97.1 ± 25.3° here against 69.4 ± 17.5° for lower-ranked professionals (p = 0.017), and this window's midpoint is 100°. But those two spreads overlap heavily, and our trophy frame is not exactly their event, so read this as a shape that is right or wrong — never as a ranking.

Where your hitting elbow sits against your shoulder line at the trophy — level is the checkpoint. A drooping elbow is the first domino of the tray.

Whether your wrist actually falls below your elbow behind you — the fold that lets the racquet head drop. If this never goes positive, the serve is a push, not a throw. This window is self-calibrated and cannot be anchored to published values: what the literature measures at the racquet drop is shoulder external rotation, a twist about the upper arm's own axis that barely moves any body point a camera can see, so no published number describes this wrist-below-elbow fold.

How high your tossing arm reaches at its peak — read from your arm, not the ball. A long, tall toss arm is the platform the serve stands on.

Whether your tossing arm stays long at the trophy. A straight arm tosses with the shoulder, and that’s what makes the toss repeat.

The time from your tossing arm’s full reach up to the hit. Enough for a real trophy, not so much that you’re waiting under a moonball. This window is self-calibrated and stays that way: the published serve durations start their clock at the ball leaving the hand, which is earlier than our start, and the same studies find the serve's timing barely moves with skill — 0.92 s against 0.94 s between a 155 km/h group and a 130 km/h one. A rushed or stalled rhythm is worth naming; your time here is not a measure of how good the serve is.

The bend in your hitting arm at the trophy. Around a right angle stores the throw; a straight arm at this checkpoint has nothing left to release. Checked against the one study that splits professionals by ranking and left where it was: top-40 WTA players hold 97.1 ± 25.3° here against 69.4 ± 17.5° for lower-ranked professionals (p = 0.017), and this window's midpoint is 100°. But those two spreads overlap heavily, and our trophy frame is not exactly their event, so read this as a shape that is right or wrong — never as a ranking.

Where your hitting elbow sits against your shoulder line at the trophy — level is the checkpoint. A drooping elbow is the first domino of the tray.

Whether your wrist actually falls below your elbow behind you — the fold that lets the racquet head drop. If this never goes positive, the serve is a push, not a throw. This window is self-calibrated and cannot be anchored to published values: what the literature measures at the racquet drop is shoulder external rotation, a twist about the upper arm's own axis that barely moves any body point a camera can see, so no published number describes this wrist-below-elbow fold.