Polyester string hides your mishits and that is the problem

A stiff bed keeps off-centre balls in play, which feels like forgiveness and quietly removes the feedback that fixes contact.

Hit a ball an inch above the centre of a soft stringbed and you know instantly. The frame twists a little, the shot floats, the sound is wrong. Hit the same ball on a tight polyester bed and quite often it goes in, low and heavy, and you learn nothing.

That sounds like an advantage. In a match it sometimes is. As a training environment it is a problem, because contact quality is learned almost entirely through feedback, and a string that flattens the difference between a good strike and a poor one removes the signal a player needs.

The mechanics behind it are straightforward. On an off-centre hit the ball's momentum acts through a point away from the racquet's long axis, so the head rotates, and the face angle at separation is not the angle the player set. That rotation is what sends a mishit sideways. Anything that resists it, whether higher torsional stiffness in the frame, a denser pattern, or a stiffer string that deforms less, reduces the angular error and the ball departs closer to the intended line.

So the modern setup is genuinely more forgiving on direction. It is also less forgiving on depth and on the arm, and the player never gets told which of his shots were struck properly.

I coach around it in a way some people will disagree with. Practise with a softer bed, at least in the first half of a session. Let the frame tell the truth. Take the poly for matches if the extra control is worth it, but do not spend every hour of the week in a setup designed to conceal the exact fault you are supposed to be correcting.

There is a broader version of this. Racquets got wider and stiffer, strings got firmer, and the modern frame forgives a lot. As a result the average club player's contact point is worse than it was thirty years ago and his results are better, and he has no idea, because the equipment absorbed a fault that used to be self-correcting.

Every so often, borrow a small headed frame with soft string and hit for twenty minutes. It is a humbling exercise and it will tell you more about your strike than any camera will.