Perhaps the single-best thing you can do to improve your golf swing in the gym is improve your body's stability. Most trainers will tell you that stability is crucial to having the mobility to make a proper backswing, creating power, delivering the club on-plane and hitting the ball on the center of the face. You've probably heard the old adage that you can't fire a cannon from a canoe. In golf, any good shots that stem from an unstable, off-balance swing are almost always a happy accident.
All the various plank exercises for your abdomen also will help improve stability when you swing.
But one product that takes the concept of stability training in a whole new direction and might be worth adding to your gym equipment is the ActivMotion Bar (activmotionbar.com). It looks like any other weighted bar, but inside its cylinder are mobile weights. As you move while holding one, the weights inside shift from one side of the bar to the other because of gravity, and that forces you to re-stabilize the body in order to maintain balance and perform the exercise functionally. This constant flux between being stable and unstable is the secret to ActivMotion's benefit for golfers. It mimics the relationship between your body and your club as you make a golf swing. Unless you preserve stability when you swing, you'll either lose your balance, or make an off-center hit—or both.
Although the company offers bars of various weights and sizes, the one that they say is best for golfers is the 4.5-pound model that fits into a golf bag ($120). If you want to see their products in action, click on the video below:
Ron Kaspriske is the fitness editor of Golf Digest.