Your strings lose more tension in the warm-up than in the pro shop

Tension drops steeply in the first hour of play, so the number chalked on the frame describes a racquet you stopped using immediately.

A player asks for fifty two pounds, the machine pulls fifty two pounds, and the frame leaves the shop labelled accordingly. By the end of the warm-up it is not fifty two any more. Polyester in particular sheds tension quickly, a noticeable chunk of it in the first twenty minutes of hitting and more over the following hour, and the frame keeps losing it sitting in the bag overnight.

So the number on the throat is a starting condition, not a description. Every argument about one or two pounds is an argument about a value that survived less time than the changeover.

This explains something players find mystifying. The racquet feels perfect in the second set and dead by the fourth, and the same frame feels boardy again the following week after resting. Some of that is the string bedding in, some is it losing elasticity permanently, and the practical effect is that a player is using a slightly different racquet at every stage of a long match.

Which is the real argument for carrying multiple frames, and it is not the one usually given. People say you need spares in case one breaks. The better reason is that a professional wants every frame in the bag to be at a similar point in its life, so the racquet after the changeover behaves like the one before it. Strung the same day, hit in for the same time. If you own two racquets and one is fresh and one is three weeks old, you have two different rackets and you will feel it on the first volley.

My own view, and stringers will argue with me here, is that most club players are chasing tension when they should be changing string more often. A dead poly bed at any tension plays worse than a fresh one at roughly the right tension, and the old rule about restringing as many times a year as you play per week is still the most sensible advice in the sport.

There is a hedge worth knowing. Cooler and damper conditions stiffen the ball and slow the court, warmer conditions do the opposite, and a pound or two either way is a reasonable response.

But if you have not cut the strings out since spring, do not talk to me about tension.