Wrist hinge in golf: three axes, one clubface

Two of the three happen at the wrist

23.2° against 166.6°Radial deviation against total forearm rotation, men's dominant side

Hold a club and the hand can do three separate things. It can bend toward the palm and back toward the forearm, which anatomy calls flexion and extension. It can tilt thumb-side up and little-finger-side down, radial and ulnar deviation. And the forearm can roll the hand over, pronation and supination. Golf folds all three into wrist action. The third is not a wrist movement.

The distinction matters because the three have very different budgets. Fan and colleagues measured 30 healthy volunteers aged 23 to 30 with goniometers, elbows bent to 90 degrees. The men's dominant side, forearm neutral, gave 70.2 degrees of flexion, 65.6 of extension, 37.2 of ulnar deviation and 23.2 of radial deviation. Forearm rotation dwarfed the lot: 87.7 degrees of supination and 78.9 of pronation.

The axes also interfere with each other. In that same group the men reached 15.4 degrees of radial deviation with the forearm supinated and 23.9 with it pronated. Where your forearm is rolled to decides how much sideways travel the wrist still has, so a grip change can move a number you were not working on.

Hinge, cock and set are not fixed terms

Titleist Performance Institute screens the up-and-down axis under the name Wrist Hinge Test (Radial-Ulnar Deviation), and asks the golfer to hinge the wrists up and down with the elbows bent and thumbs up. HackMotion's article on the same axis puts it as an equation: radial deviation hinges the club upward, ulnar deviation unhinges it downward. Two sources, one meaning. Then the same page sets a drill.

Raise the club to parallel from address, it says, and that should create roughly 90 degrees of hinge. Nobody owns 90 degrees of radial deviation; the clinical figure above is 23. The 90 is the angle between lead forearm and shaft, a pair of lines in a photograph. Carson, Richards and Mazuquin note that earlier golf research defined the wrist the same way, by the shaft moving relative to the forearm, which is why their data sit in one or two axes.

How far each axis travels in a driver swing

61.7°, 63.4°, 45.2°Lead-wrist travel on each axis, neutral grip, twelve professionals

The same paper ran twelve professional coaches through a ten-camera Qualisys system sampling at 300 hertz, tracking each hand against its own distal forearm on all three axes at once. Under a neutral grip the lead wrist covered 61.7 degrees of flexion and extension, 63.4 of ulnar and radial deviation, and 45.2 of axial rotation. The trail wrist covered more of the first two, 77.9 and 73.3, and less of the third, 32.0.

One entry in that table is worth stopping on. The lead wrist's most radially deviated position averaged 34.7 degrees, larger than the 23.2 a goniometer records as a maximum. Read that as two instruments disagreeing rather than golfers beating their own anatomy. Marker sets, zero positions and segment definitions all differ, so figures from a laboratory, a forearm sensor and a clinic will not convert into one another.

The axis named for the clubface moves it least

Face tolerance is what makes the question sharp. Adam Young puts a tour-average iron shot inside a 3.4-degree face window, and one degree of driver face at around 12 yards offline over 240. An axis carrying a cue about squaring the club has to move the face by a few degrees.

Carson's grip conditions test that. Moving the hands to weak, neutral and strong significantly shifted flexion and extension, and axial rotation, in both wrists at every swing event, and moved the clubface angle at impact with them. Ulnar and radial deviation barely responded. The axes that tracked the face were the ones the hands rotate about. Where lead-wrist flexion sits at the top has its own guide, and so does the rate the face turns through impact.

Deviation is not idle, though. Fedorcik and colleagues at Duke filmed 28 male golfers on an eight-camera system, fifteen at 0 to 5 handicap and thirteen at 10 or worse, and found the high-handicap group significantly more radially deviated at its peak and at ball contact, at 5.7 and 7.1 degrees. The abstract does not say whether those are group angles or the gap between groups, and the paper is paywalled.

What one lens can separate, and what it cannot

A camera measures the angle it is shown. Bending and tilting both change the outline of the forearm and hand in the picture, so a frame carries part of them. Rolling the forearm turns the hand about an axis running down the arm, and that turn hides inside the silhouette. It is the movement a single lens gives up first.

The laboratories are not unanimous either. Carson treats the hand's axial rotation against the distal forearm as rotation at the wrist joint, distinct from pronation and supination at the radioulnar joint. Robinson and colleagues, recording fifteen sub-elite golfers with sensors on forearm and hand, write that the hand's rotation velocity is equivalent to forearm rotation, because pronation and supination occur at the radiocapitellar joint.

Pebble Swing reads joint angles out of the frames, along with the backswing-to-downswing tempo ratio, and any wrist angle taken from a photograph blends the three axes into one. Keeping them apart takes a sensor worn on the arm, and the axis it adds is the one your clubface notices.