The forehand that eats your lower back

Modern heavy topspin is generated by rotating hard against a planted leg, and the bill for that arrives in the lumbar spine.

Watch a slow-motion replay of a big open-stance forehand and pay attention to the hips rather than the arm. The outside leg loads, the hip fires, the torso rotates while the shoulders lag behind, and then everything unwinds through contact. It's a beautiful bit of kinetic chain and it produces a ball that no amount of arm strength could match.

It is also a rotational load applied repeatedly to a spine that isn't especially good at rotating.

The lumbar vertebrae have very limited rotational range. Most of your torso's twist should come from the thoracic spine and the hips. When either of those is stiff, and in a lot of players the thoracic spine is extremely stiff because they sit all day and nobody stretches upward, the lumbar segment takes the difference. Add several thousand repetitions a week and you get the pattern every tennis physio recognises: a sore lower back on one side, worse after serving, worse on a slow court where you have to generate more of your own pace.

The serve is the other culprit and it's arguably worse, because the kick serve requires extension and rotation and side-bending all at once, which is about the least friendly position you can ask a lumbar spine to produce force in. That combination is why stress-related back problems are a young player's injury in this sport rather than an old player's.

Here's the part that annoys me. The response is almost always more core work. Planks, dead bugs, endless anti-rotation cable holds. Those aren't useless, but a stronger brace around a joint that's being asked to move beyond its range doesn't solve the range problem. What actually helps is thoracic mobility and hip internal rotation. If your back hip can't rotate, your forehand steals the movement from higher up, every time, and no amount of abdominal strength changes that.

There's also a technical lever nobody wants to pull, which is simply hitting fewer maximum-effort spin forehands. Not everything needs to be heavy. A flatter, more compact drive taken early off the bounce covers a lot of the same tactical ground with a fraction of the rotational cost, and it's the shot that tends to disappear from a player's game once they discover how much spin they can generate.

Topspin is a wonderful tool. It's just not free, and the invoice goes to a part of the body that stays quiet until it doesn't.