Rotation
Golf is a rotational sport. It’s no different from baseball, hockey, shot put–anything that requires the trunk to twist from one direction to another in ballistic fashion. For that to happen effectively, the muscles that allow you to walk upright and maintain various postures have to be strong. Even the simplest tasks such as reaching out and lifting an object require assistance from the muscles that are located in the mid-section of the body.
By now, you’ve probably heard these muscles referred to as “the core.” Many people mistakenly think the core are the six abdomen muscles, including the rectus abdominus (six-pack muscle). The abs are only part of the core. The gluteal muscles (butt), hip muscles, latissimus dorsi and erector spinae muscles (back) also are considered part of the group.
The point is, without a strong core, which provides stability for the rotational power needed to swing a golf club effectively, you might as well take up chess.
A lack of core stability is a major issue with amateur golfers. Amateurs who have weak cores can’t make an adequate turn off the ball and/or stop their swing just past impact. Many of them easily lose their balance when they swing. A great analogy would be to think of trying to swing your driver on a ice hockey rink versus a basketball court. Without stability, an aggressive swing is going to get out of control in a hurry.
There are dozens of muscles that will improve core stability. The plank exercise is one of the best to engage and strengthen much of the core. The problem with planking, however, is that the shoulders often fatigue before the core muscles do.