Omne Trium Perfectum

"Omne trium perfectum" means that all things that come in threes are perfect - now also in the sense of golf biokinetics. Although big picture studies rarely deal with small movements of distal limbs joints such as wrists and they rather treat them as loose chains between two sticks of a nunchaku there are nonetheless important correlations that influence the chain of events and help in automating also in this area.

It is worth noting that the most usual movement of the wrist is one of dorsi flexion (extension) combined with radial deviation, and of palmar flexion combined with ulnar deviation. Pure palmar-dorsal flexion (flexion-extension) and radial-ulnar deviation are movements that rarely occur in a straight plane. It is like that because when we want to maximize ulnar deviation range we unintentionally bow the wrist which means we flex it palmarily; conversely, when we want to maximize radial deviation range our wrist becomes dorsally flexed. It should give us the picture that the axis of wrist deviation RoM is not parallel to pure deviation motions but is slanted from slight palmar flexion to slight dorsal flexion.

This phenomenon brings the third type of motion in force, namely, supination and pronation of the forearm. When we assume that full ulnar deviation must be accompanied by palmar flexion we have to observe that it must also be accompanied by slight supination of the forearm. There is no other choice. We can add that of course full radial deviation would not only require slight dorsal flexion but also slight pronation of the forearm. This is why motions in threes are so efficient in the wrist area.

Now the best part - the first three, i.e. ulnar deviation, palmar flexion and supination are gravity-friendly movements that happen unintentionally in the downswing phase. They are useful even more for a golfer that stands circa 90 degrees closed to the target because of supination movement that is quite normal because elbow joint has a limited RoM and it is not possible to avoid lead forearm pronation going back and, consequently, its supination going down.

Therefore, we not only should have no fear about controlling our wrists via any conscious actions or unnecessary training - nature cared sufficiently enough to join movements in pairs and sometimes, as in this example, also in threes to ease the kinetic goal.

Furyk's Case

There is one of the best ever pivot-driven action between the reaching of the EEP and late follow-through. The only one today that is in post-secret Hogan's league when talking about maintaining the clubface square to the swing arc the longest possible time in the motion.
Pay attention not only how his clubface remains square to the arc but how his rear humerus work parallely with his hard pivoting body. No strange Jim Furyk is being regarded as the most consistent ballstriker of our era even by Trackman specialists.

Click on a photo to enlarge it if necessary.

It is a great action. It is worth adding again that Mother Nature made the elbow joint the way it cannot move in all possible directions because it would be too weak to support a lot of physical activities correctly; therefore, hard structure needs additional motions of forearm to adjust the lack of RoM in the elbow joint to allow some physical actions to be achievable. One of this motion is pronation/supination of the forearm (turning the forearm axially without necessity of moving the elbow joint in space). Physics of golf swing must include pronation/supination (and bending the rear elbow as well, BTW) because otherwise one couldn't make a full swing.
Now, when rear forearm pronates (during downswing) it affect simultaneously the shaft and the clubface. It is much easier to control the clubface when shaft is aligned parallelly - or better said - is a parallel extension of pronating body part. Any angle between it (i.e. when shaft is not parallel) forces an additional action of wrist to adjust to impact.
Probably this is one of main reasons why the most consistent ballstrikers were elbow planers with their rear forearm supporting the shaft and rear humerus tight to the body. Other reason was that their pivot was great enough to let the above occur. It requires the rear elbow joint be on the rear hip at impact. The more the elbow goes in front of the body the worse for the whole motion. People often say "stuck" incorrectly.The rule of thumb is -- the stronger the pivot is the more open is main body at impact (hips more, shoulder girldle less of course due to sequentiality) and the more is the lead arm pinned accross the chest while the rear elbow close to the rear hip.