Everyone wants a bigger serve, and almost everyone chases it the wrong way: by swinging harder with the arm. It's the natural instinct and it's a trap. A serve muscled out of the arm is slower than it feels, streakier than you want, and the fastest way to leave your shoulder aching. Real serve power comes from two places, and neither of them is "try harder with your arm."
Where serve pace actually comes from
The legs. Your legs are the biggest engine in your body. Loaded at the trophy and driven up into the ball, they launch your whole body upward — and that upward launch is free contact height and free racquet-head speed. This is the safest power source there is: pace that rises up from the ground costs your shoulder almost nothing, while pace forced out of the arm costs it plenty.
The racquet drop. Before the racquet flies up, its head falls behind your back — the back-scratch. A loose arm lets that fall happen, and the release of it whips the racquet through faster than any amount of muscling could. Effort actually blocks this: a tight arm holds the racquet up and never lets it drop, so there's nothing to release.
Put simply: the fastest serves are the most relaxed ones. The power comes from timing a leg drive and a loose drop, not from swinging like you're angry at the ball.
What the camera reads
CoachVision measures leg drive as how much your hips rise from your deepest knee bend up to contact, in torso-lengths. That rise is your legs launching you at the ball; near zero means the engine never fired. Alongside it, the racquet-drop fold tells you whether the arm actually let go. When both are alive — hips rising, wrist folding below the elbow behind you — you've got the two real power sources switched on. When you're chasing pace with a stiff arm instead, both tend to read flat while your effort reads high.
One honest limit worth stating plainly: the app never gives you a serve speed. There's no mph or kph anywhere — the tracker measures your body, not the ball. What it measures is where your power is coming from, which is the thing you can actually change.
The drill — Load-and-Explode Serves
Route your power search into your legs. Exaggerate the knee bend at the trophy, then drive up and into the court, landing on your front foot inside the baseline. Let the legs throw you at the ball and keep the arm loose enough to feel the racquet fall on its own.
Twelve serves at a smooth pace — not a hard one. Chasing power at full effort just reintroduces the arm tension you're trying to escape. Find the speed at a pace you can hold the shape at.
Then film a side-on serve and watch the hip rise appear and the drop deepen. The day you feel a serve launch off your legs with a loose arm is the day you learn the secret every big server knows: the biggest serves are thrown, not muscled — and they're the ones your shoulder will thank you for.