The serve is the only stroke that hurts you when you do it correctly

Modern serving asks the trunk to hyperextend and rotate under load, and the abdominal tears that follow are a design feature.

A stress fracture in the lower back of a teenage server is not a technical fault, and neither, mostly, is the torn abdominal that ends an autumn. Both are what happens when a body executes the modern kick serve exactly as coached.

The action is genuinely strange. To hit up on the ball and impart heavy topspin, a right hander arches back and to the left, then unwinds through a diagonal that combines extension, side bending and rotation, all while the shoulder is externally rotated to a degree that would look like an injury in any other context. Peak loading falls on tissue that is already at length. The rectus abdominis on the non dominant side takes it, and so does the pars interarticularis on the dominant side of the spine.

You can see why coaches teach it anyway. A serve with real kick opens up the whole second serve strategy and stops a good returner standing inside the baseline, and a player without one is playing three quarters of a match. So the sport keeps producing an action with a known cost and then treats the cost as bad luck.

What can actually be done is duller than a technical fix. Manage the volume of kick serves in practice separately from total serve count, because a hundred flat serves and a hundred kickers are not the same session for the trunk. Build genuine anti extension and anti rotation strength rather than the endless crunching that still passes for core work in some academies. Watch teenagers through growth spurts, when the spine is least tolerant of repeated extension and the temptation to add a weapon is highest.

I would go one further, and here I expect disagreement. Junior competition schedules should cap serving loads the way youth baseball caps pitch counts. Baseball took years to accept that the elbow of a fifteen year old was a finite resource and the result has been a measurable reduction in a specific catastrophic injury. Tennis has the identical problem in the shoulder and lower back and no equivalent rule, only advice.

The counter is that tennis serving is less traumatic per repetition than pitching, which is true, and that players serve far more repetitions, which is also true and rather undercuts it.

We have decided that the best shot in tennis is allowed to be the one that quietly ends careers.