Head sway, hip slide, shoulder tilt and early extension: four movements worth measuring
What each of these body movements is, why golfers and coaches watch for them, and how a video-based measurement decides whether yours is unusual or just yours.
Coaches have a vocabulary for how a body moves during a swing. Most of it is descriptive — “you’re swaying”, “you’re standing up” — and most of it is judged by eye. That’s fine when the eye belongs to a good coach. It’s less fine when you’re on your own at the range trying to work out whether the thing you felt is the thing that happened.
Here are four of the most common movements, what they are, and how you’d put a number on them.
Head sway
What it is. Your head moving sideways — toward or away from the target — during the backswing.
Why people watch it. A head that drifts a long way away from the target on the backswing has to come all the way back before impact. Many golfers manage that; many don’t, and the ones who don’t tend to hit the ground in different places from swing to swing. A small amount of movement is normal. There is no single correct amount.
How to measure it. From a face-on video, track the head’s horizontal position at address and at the top, and express the difference as a fraction of something stable — shoulder width is a common choice, because it makes the number independent of how far away the camera was. A swing with head movement of 0.3 shoulder-widths is directly comparable to one filmed from a different distance.
Hip slide
What it is. Your hips shifting sideways toward the target early in the downswing, rather than rotating.
Why people watch it. Some lateral movement toward the target is part of most swings. A lot of it — hips sliding well past where they started before they turn — is often paired with the upper body hanging back, and coaches tend to flag it. Again: a range, not a threshold.
How to measure it. Face-on video. Track the hip centre’s horizontal position from the top of the backswing to impact, scaled to shoulder width, same as above.
Shoulder tilt
What it is. The angle of the line between your shoulders relative to horizontal, usually looked at at the top of the backswing and at impact.
Why people watch it. Shoulder tilt is part of how the upper body turns and how it delivers the arms. Very flat shoulders at the top and very tilted shoulders at impact each get commented on, in opposite directions, for different reasons.
How to measure it. Face-on. The angle of the shoulder line at each phase is a straightforward two-point angle, and it’s one of the more reliable figures you can get from 2D video, because the shoulders are usually clearly visible.
Early extension
What it is. Your hips moving toward the ball — away from where they were at address — during the downswing, so that your body “stands up” out of its posture.
Why people watch it. It is probably the single most commonly mentioned movement in amateur swings. When the hips come forward, the arms have to find room somewhere else, and the swing changes shape to compensate.
How to measure it. Down-the-line video only — face-on can’t see this. Track the hip’s position relative to a reference line dropped from where it was at address and see how far forward it gets by impact. This one is sensitive to camera placement: a camera that isn’t on the target line will measure a slant instead of a slide, which is why an honest tool will decline to report it from a face-on clip.
What the numbers are compared to
A raw figure — “your head moved 11 cm” — means nothing on its own. The useful question is: compared to what?
The honest answer is compared to a population of other measured swings. If you measure the same thing the same way on a few hundred swings, you get a distribution. Your number lands somewhere in it. If it lands where 9 in 10 of the others do, it’s unremarkable. If it’s out past where 95% of them sit, that’s worth knowing.
What that comparison doesn’t do is tell you that you have a fault. Populations of golfers include good and bad swings, and the tails of the distribution aren’t automatically the wrong place to be. It tells you that your swing is unusual on this axis — the decision about whether to change it belongs to you and, ideally, a coach.
Camera angle decides what you can trust
A quick reference:
| Movement | Face-on | Down-the-line |
|---|---|---|
| Head sway | ✓ | — |
| Hip slide | ✓ | — |
| Shoulder tilt | ✓ | partial |
| Early extension | — | ✓ |
Any tool that reports early extension from a face-on video, or head sway from a down-the-line one, is guessing. Ask it which frames and which angle it used. If it can’t say, don’t act on the number.