Swing One and Swing Forty Are Not the Same Golfer

The premise of a club fitting is that we can hold the golfer constant and vary the equipment. Every conclusion on your sheet rests on that premise. It is also, taken literally, false: a person is not a test rig, and over ninety minutes the person changes in ways that are neither random nor small.

We started photographing address position at fixed intervals during blocks about four years ago, mostly out of curiosity. What came back was consistent enough that it reorganised how the studio runs an appointment.

The Four Things That Move

Four measurements drift reliably across a session, and they drift in a recognisable order.

Ball position goes back. Almost universally. A golfer who starts with the ball inside the lead heel finishes the session with it half a clubhead further toward the middle of the stance. The average drift we record across a ninety minute block is a little over half an inch, and the largest we have measured on a single golfer was two and a quarter inches.

Stance width narrows, then widens. It narrows during the first twenty minutes as the golfer loosens, then widens again in the last third as fatigue arrives and stability starts to feel more attractive than mobility. The net figure at the end often looks like nothing happened, which is exactly why sampling only at the start and end is misleading.

Handle height creeps up. Fractionally, and mostly late. It correlates with tiredness more than anything else, and it drags the effective lie angle with it.

Aim opens. Body line drifts right of the target for a right-handed golfer, roughly two degrees over a full block, and the golfer's subjective sense of aiming straight does not move at all.

Why the Direction Is Predictable

None of this is mysterious once you watch enough of it. Ball position goes back because a golfer who is hunting for contact gravitates toward the position that produces the most reliable strike, and for most amateurs that is further back than the position that produces the best flight. The body optimises for the immediate feedback it can hear, which is the strike, rather than the delayed feedback it can barely see, which is the flight.

Aim opens because the golfer is standing on a mat next to a fitter, talking, turning to look at a screen, and re-taking their stance forty times without an external reference. Every re-take inherits a fraction of the previous one's error. That is a ratchet, and ratchets only turn one way.

Nobody drifts on purpose. That is the whole problem: the golfer has no idea it happened, so they will tell you honestly that nothing changed.

The Size of It, Against What We Are Measuring

Half an inch of ball position on a seven iron is worth roughly a degree of dynamic loft in the typical case. A degree of dynamic loft is worth several hundred revolutions of spin and a couple of yards of carry. Those are the same magnitudes we are trying to resolve between two shaft candidates.

So if a golfer tests shaft A in minute twenty and shaft B in minute fifty, and their ball position moved back half an inch in between, the sheet will show a difference that has nothing to do with either shaft. It will be a perfectly real difference, correctly measured, and completely useless.

This is the single strongest argument for the way this studio sequences an appointment, and it is also the reason a thirty minute fitting cannot be honest about small differences. There is no time in thirty minutes to establish a baseline, let alone to re-check it.

What We Do About It

Three habits, none of them complicated.

Marks on the ground. Ball position and stance width are marked with tape on the mat at the start of the block, referenced to the lead heel. Re-taking the stance against a physical reference removes most of the ratchet, because each re-take inherits the mark rather than the previous attempt.

Re-checks between test groups. Every time we change what is in your hands, the fitter looks at the marks before the first strike counts. It takes four seconds and it catches the drift that survives the tape.

Interleaving, not sequencing. Where a comparison really matters we do not run six shots of A then six of B. We run A, B, A, B in pairs. Whatever drift occurs is then spread across both candidates rather than loaded onto the second one. This is the least intuitive of the three and the most effective.

The Bit Golfers Find Uncomfortable

Showing somebody a photograph of their address position at swing four beside one from swing thirty-one is occasionally a difficult moment. The two frames often look like different people, and the golfer's first reaction is usually that the camera moved.

It did not. The camera is bolted to a fixed mount and the frames are aligned on the same reference marks. What moved was a person who had been standing to a golf ball for forty minutes, exactly as any person would.

The useful reframe is that this is not a fault to correct. It is a property of the measuring instrument, and the instrument is you. A fitting that does not account for it is not measuring equipment, it is measuring your last hour.

What It Means for Your Own Practice

Outside of a fitting the same drift is happening on every range session you have ever hit. The last twenty balls of a bucket are struck from a meaningfully different setup than the first twenty, which is one reason range performance and course performance diverge so reliably.

If you take one habit away from this note, make it the alignment stick on the ground, and make it the one thing you never practise without. It is the cheapest measurement device in golf and it removes the largest uncontrolled variable in the sport.