Heavy topspin is paid for at the wrist before anywhere else

The brushing action that generates modern revolutions loads a small tendon on the little-finger side of the wrist.

Ask where a modern forehand hurts and most people point at the elbow. Watch the injury lists and the wrist keeps winning.

The reason sits in how spin is actually generated. Racket head speed comes from the shoulder and the trunk, but the brushing angle, the low-to-high path with the face closing across the ball, is finished by the forearm rotating and the wrist moving toward the little finger side at the exact instant of contact. That position, with the forearm turned over and the wrist deviated, puts one particular tendon at the back of the wrist under both tension and a sideways bend where it wraps around the end of the ulna. The sheath that holds it in place is not large and it is not deeply protected.

Add the impact. A ball struck with a lot of spin is contacted with the face moving fast across it, which means a glancing hit rather than a flush one, and a glancing hit sends more twist through the handle. Modern grips make it worse in the sense that the more extreme the grip, the more of the swing has to be delivered by forearm rotation, because the shoulder alone cannot get the racket face where it needs to be.

Now consider the two hander, where the non-dominant arm does most of the work. That arm is effectively hitting a forehand, and in players with a strong two handed backhand it is usually the left wrist in a right handed player that goes first. If it were a general impact problem it would follow the racket hand. It follows the brushing hand.

Which brings me to the part I actually want to argue. We describe heavy spin as a safety feature, because it lets you swing full and still land the ball inside a court, and that framing is true for the ball and false for the body. The safety is bought by adding a rotational demand at the smallest joint in the chain, and small joints do not have large muscles to absorb what they are given.

Watch a player come back from wrist surgery and notice what changes. Flatter. Earlier contact. Less brush. It looks like a tactical adjustment. It is a structural one, and it is usually permanent.