Head movement in the golf swing, measured

Eight golfers, two skill levels, and millimetres

54.66 mmSideways head travel at the top, four golfers off a mean handicap of 4.5

Derek Byrne and Ian Kenny of the University of Limerick filmed eight male golfers driving indoors: four off a mean handicap of 4.5, four off 17.8. Six cameras at 200 Hz tracked 29 markers, seven swings each. Head movement was defined as travel away from the address position, in millimetres.

In the frontal plane, the sideways axis a face-on camera reads best, the low-handicap four had moved 54.66 mm by the top of the backswing, standard deviation 29.56 mm. The higher-handicap four had moved 123.68 mm. Two inches against nearly five. Neither group was still.

At impact the figures were -31.18 mm and 52.33 mm. The sign flips for the better players and not for the others, so their heads had crossed back past the address position by the time the club arrived. The higher handicaps' had not.

What the paper leaves open

About 6xHow much further the higher-handicap group's head travelled on the second axis

The second axis goes untidy. Travel at the top was 19.66 mm for the low-handicap group and 117.8 mm for the other, on an axis the results name as the sagittal plane and the conclusion calls vertical. Different planes, so the size of the gap is clear and its direction is not.

The paper never states which direction counts as positive either, so the minus sign at impact places the head on the far side of address without saying which side. The sample is four golfers per group, published as preliminary results, and that standard deviation is more than half its mean.

These were Irish club golfers, not tour players, so treat 55 mm as an observation about four good amateurs rather than a number to hit. The ratio is the durable part: roughly twice the sideways travel, six times the travel on the second axis.

The cue is wrong about the wrong quantity

Most golfers meet this as "keep your head down". Tony Ruggiero, a GOLF Top 100 Teacher, calls that one of the worst things you can do, because holding the head down restricts the upper body from moving through and tends to make the club bottom out behind the ball.

The true observation sits in the gap between the groups. Something in the better players' swings held a centre: half the sideways travel, a sixth of the travel on the other axis. What the cue gets wrong is the quantity. It asks for zero, and neither group produced zero.

It also names the wrong part. Cameron Kelly, writing for GOLFTEC, has the better version: good golfers rotate rather than sway, and what stays put is the centre of the chest and pelvis. The head got the cue because the head is the part you can see.

What Nicklaus said, and what Strange did

Jack Nicklaus is on record at the strict end. Quoted by GOLF Top 100 Teacher Kevin Sprecher, he described feeling a shaft running down through his head and revolving around it, and told golfers to keep the head "right there, dead still".

Dean Reinmuth's Tension-Free Golf, from 1995, puts Curtis Strange at the other end. Reinmuth lists him among players whose form broke a rule and whose golf did not, writing that Strange moves his head well off the ball on his backswing. Neither description carries a number.

Sprecher's guide is the checkable version: with a driver the head starts behind the ball, moves back a little further going back, and some backward movement at impact helps the club swing up; with irons it re-centres by impact. Mike Perpich puts the downswing feel as the head moving away from the target while the lower body shifts toward it.

Measuring yours from a face-on frame

1.680 in / 42.67 mmDiameter of a conforming golf ball, the ruler already in your frame

Beyond a normal face-on clip this needs one thing: a fixed background. A fence post, a range bay divider, a doorway indoors, or an alignment stick pushed into the ground behind you gives a vertical edge that does not move. The phone must not move either, and the zoom must stay where it was.

Freeze three frames: address, top of the backswing, impact. Choose one repeatable point on your head, the ear or the front corner of the cap peak, and note where it sits against that background edge in each. What you have is a distance in pixels.

The ball converts it. Under the R&A's Rules of Equipment a conforming ball is at least 1.680 inches across, or 42.67 mm, so the ball in the same frame is a ruler of known width. Count the movement in ball-widths. Byrne and Kenny's 54.66 mm is about one and a third; 123.68 mm is nearly three.

Two limits. One lens records the directions inside the frame and infers the one running toward it, so a head moving closer to the camera will not show. And nudge the phone between clips and the background moves with it, which reads as head movement. Pebble Swing reads joint angles and the ratio of backswing to downswing time out of the frames; millimetres of head travel is not among its outputs.