In the previous chapter, we addressed the movement of the lead upper arm in the shoulder socket. Now we'll talk about the rotation of both upper arms in their shoulder sockets. To understand this rotation, start by holding your right upper arm straight out in front, make a 90 degree bend between your upper and your lower arm, and point your lower arm upward so that it is vertical to the ground. Loosely grab your upper arm with your left hand to hold it in one place, without impinging on its movement. Now, rotate your lower arm inward toward the centre of your body, then back to the start position, and then outward to the extent possible.
This movement occurs because your upper arm is rotating in its shoulder sockets. You can see this rotation if you focus on your elbow. Out the outset, it is pointing down. When you rotate your lower arm inward, your elbow points outward away from the body.
You should be able to rotate your lower arm inward about 90 degrees from the start position (lower arm up, elbow down) to the finish position (lower arm horizontal, elbows out).
Return to the start position (lower arm vertical, elbow down) and try to rotate your lower arms away from the centre of the body. You should experience relatively little movement outward.
The total rotation from moving the lower arms inward and outward is about 90 degrees. Most of this occurs when the forearm is rotated inward so that the elbow points outward.
The ability to rotate the upper arm in the shoulder socket arises from the fact that the shoulder joint is a ball and socket joint. This ability is the result of muscles contracting around the shoulder joint.
You can get a feel for which muscles are involved by allow your upper arms to hang vertically at your side from a standing or sitting position, and rotating your upper arm quickly and repeatedly clockwise and counter-clockwise. In time, you should begin to feel the burn as the muscles around your shoulders fatigue. If you do not feel this burn, hold a light weight and repeat the exercise.
In the golf swing, grip your club in front of you with the thumbs on top of the shaft. Both elbows will be pointing down. The lead upper arm can rotate about 90 degrees, with the elbow moving from down to outward in the backswing, and outward to down in the downswing.
This rotation adds to the forearm rotation discussed in Chapter 3. In that Chapter, we noted that forearm rotation adds power to the golf swing. The rotation of the upper lead arm in the shoulder socket adds to the forearm rotation.
To support the rotation of the lead upper arm in the shoulder socket, one would want the trailing arm to rotate in the same direction. However, the trailing arm starts initially in a position that is essentially down; it cannot rotate inward to any significant degree. As such, it does not supplement the rotation of the trailing forearm at the elbow. Since the lead and trailing arms are linked through the grip and work together, the lack of rotation in the trailing arm limits the rotational effect of the lead arm to less than the 90 degrees that it could achieve on its own. The overall rotation of the golf club from the rotation of the lead upper arm in the shoulder socket combined with the lack of rotation of the trailing upper arm in the shoulder socket is approximately 45 degrees.
We have noted that at setup, the thumb on the trailing arm is located on top of the shaft of the club. This puts the trailing elbow substantially, but not necessarily fully, at the limit of its inward rotation. To simplify the golf swing, it is useful to rotate the trailing upper arm inward to the limits of its movement in the setup, and keep it there throughout the back swing, rather than allow some inward rotation inward during the swing.
Golf analysts in books, videos or television on occasion discuss the trailing elbow. They usually make the point that the trailing elbow should be pointed toward the ground at the top of the back swing, and not pointed outward. When the elbow points outward, it is sometimes characterized as a "flying" elbow. A trailing elbow pointed outward at the top of the back swing can affect:
The proper rotation of the trailing upper arm in the shoulder socket does not add much to the back swing, but faulty rotation in the wrong direction can do damage.
A test of faulty rotation is to place an object in the armpit of the trailing arm. If the object falls to the ground during the back swing, then there is separation between the upper body and the trailing upper arm caused by the outward rotation, and the object will fall to the ground. As a practice drill, swing with the object in the armpit, and make every effort not to let the object fall to the ground until after impact.
The rotation of the lead upper arm in the shoulder socket should be clockwise for the right hand golfer on the back swing, and counter-clockwise on the downswing. For the trailing upper arm, if one starts at the limit of clockwise rotation, then there is no rotation on the back swing, but counter-clockwise rotation on the downswing. Just past impact, the counter-clockwise rotation of the lead upper arm stops as it reaches the limit of its range of movement.
Golf analysts occasionally talk about the direction of the club face at the top of the back swing in a good golf swing. The possibilities are open, square and closed. The definitions of "open", "square" and "closed" generally seem imprecise, but are directly related to the extent of upper arm rotation in the shoulder socket and forearm rotation. A lot of clockwise rotation for a right hander can be associated with an "open" club face, and minimal rotation or counter clockwise rotation associated with a "closed" club face. "Open" is more powerful.
The bending and straightening of the lead arm at the elbow is caused primarily by muscles in the upper arm. These muscles attach to the lower part of the bone in the upper arm (the humerus) and to the upper part of the two bones in the forearm (the ulna and radius). Contracting the biceps on the top of upper arm causes the arm to bend at the elbow. Contracting the triceps on the back of the upper arm causes the arm to straighten. To keep the lead arm straight, maintain the contraction of the triceps in the back of the lead upper arm from the start of the swing until after impact.
In the back swing, the lower and upper portions of the trailing arm bend at the elbow because of a contraction of the biceps. During the downswing, the trailing arm straightens because of the contraction of the triceps. Is this movement a power source in the golf swing?
The answer is no. If one assumes the setup position, and contracts the biceps of the trailing arm, the forearm moves upward. Contracting the triceps causes the forearm to move downward. The up and down movement in the golf swing does not propel the ball forward, and as such, is not a power source. The trailing arm bends to accommodate other movements in the golf swing.