Altitude changes a match more than any tactic does

Thin air alters flight, bounce and spin effectiveness at once, and it beats almost anything a coach can write on a whiteboard.

Play a tournament at height and everything you know about your own ball is slightly wrong. Less dense air means less drag, so the ball travels faster and further for the same swing, and it also means less of the aerodynamic force that makes topspin dip. Those two effects stack in the same unhelpful direction for a heavy spin player. The shot that normally drops inside the baseline now does not, and the safety margin that the spin was buying disappears exactly when the extra speed makes you need it most.

Flat hitters and big servers get the reverse deal. The serve arrives faster, the slice stays lower, and the reduced spin effectiveness matters less because they were not relying on it. This is why the results at altitude events look scrambled compared with sea level form, and why some players quietly skip them.

The bounce compounds it. Balls used at height are made differently for exactly this reason, with less internal pressure to offset the thinner air, but the compensation is approximate rather than exact and it does nothing about the flight of the ball between bounces. So you get a ball that behaves roughly normally off the court and abnormally in the air, which is a strange combination to adapt to and takes most players several days.

The adaptation that works is not tactical. It is a shortening of the swing and a lowering of the target over the net, both of which feel timid to a player who has spent years being told to swing through the ball. That is the hard part. You are asking someone to play a version of their game that feels worse in order to get a result that is better, on a court where the immediate feedback is telling them they have gone soft.

I would arrive early or not at all. Three days of hitting at height is worth more than any amount of video work.

What I do not accept is treating altitude as an excuse after the fact. Everyone plays in the same air.

It is just that the air has opinions about your forehand.