At a very late juncture in the downswing it is highly desirable that you, as a right-handed player, find yourself in a position to hit against a firm left side. This classic piece of swing advice is noteworthy because it just might be the determining factor that either makes or breaks your success as a golfer.
Once the swing has totally changed directions, the initiating movements of the forward-swing create a chain reaction of events that eventually result in the firming up of the left side. Correctly executed, this sequence of motion is rooted in good footwork. Thus, it is led by the feet with a weight shift toward the target. Then, the ankles roll toward the target, followed by the lateral movement of the knees toward the target. Next, in the chain of events, come the thighs and the hips. Trailing along behind them come the shoulders, arms, and so on and so forth.
At a later stage in the forward swing, when your arms and hands reach hip height, you’ll want to have the feeling that both hips are moving laterally toward the target. At this point, approximately 75% of your body weight should have shifted to the inside edge of your left foot; with the remainder on the inside edge of your right foot. Your right foot should propel your legs and your flexed knees laterally toward the target. Also, it is essential to keep both knees roughly level with each other – neither allowing the left knee to straighten nor allowing the right knee to collapse forward.
As you advance toward the “hitting area” and, your objective of hitting against a firm left side, a noticeable feeling of firming up, or stretching, in your left leg and side should be felt. This sensation is the result of a forward weight shift and an upward movement of your left shoulder causing the “bowing in” of your right side. Despite the left-side stretching action, both knees remain flexed and resilient, neither straightening nor stiffening at any point prior to impact and beyond.
The right side must stay “under” the left side through impact. For this to happen, the left side must provide resistance; it must be firm, extended, and stable. This left-side stability is achieved through a feeling of stretching your left side – from your left foot to the tip of your left shoulder – without, straightening your left knee.
Therefore, regardless of what you may have gleaned from listening to certain golf instructors and commentators about hitting against a firm left side, please do not conclude that they mean to imply you should stiffen or lock your left knee-joint as you deliver your clubface to the ball at impact. While straightening the left leg allows you to rotate your upper body more quickly on your downswing, it also places tremendous stress on the knee-joint.
Personal Note: As this post relates to Tiger Woods: When he pushes his weight into the ground with his left leg just before impact for the sake of a few extra yards, I believe that it’s a dangerous and controversial move that he makes which has led to the leg and knee injuries that have plagued his career.