Shoulder blades power the swing
By T.J. Tomasi
The scapula or shoulder blade is your back’s contribution to the three-bone shoulder joint. The other two bones are the clavicle and the humerus, the big bone in your upper arm. The scapula is attached to the rotator cuff, a group of four muscles that operates the shoulder. The ends of these muscles join tendons that in turn connect to your arm bone, so basically, the scapula moves your shoulder and your arm.
While your shoulder blades can work together, as they do when you hunch your shoulders forward or draw them back to stand at Marine attention, they can also move in opposite directions from the spine, as they do during your best golf swings, the ones with the maximum coil.
Swing arc and power
The length of your swing arc is one of three ways of generating power, the other two being leverage and muscle power. For maximum arc during the backswing, the scapulas move clockwise; for right-handers, the left scapula moves away from the spine while the right scapula moves toward the spine. During the downswing, your scapulas reverse — the right moves away and the left moves toward the spine.