, the swing plane
is the plane upon which you want your golf club
's head to travel. This plane is formed between: 1)
the line connecting your shoulders
the position of the golf ball
on the ground. Better golf will result as attempts are made to: understand
why the club's head should follow this plane, swing
on or below this plane on the downswing, make proper adjustments
to one's swing when the stance is not flat.
The energetic minimum of the clubhead's travel during the golf swing is on this plane. Deviations from this plane will require energetic input from the golfer. Ernie Els and Fred Couples are famous for looking effortless as they swing, mostly because they largely stay on-plane. Ernie's nickname is "The Big Easy" because of how little he appears to work while he swings. Golfers have a saying that the pros seem to exude effortless power, while the average player exudes powerless effort. Staying on-plane is one important aspect of generating effortless power.
Swinging above the plane is a result of casting or similar disastrous moves. It's an "armsy/handsy/wristy" motion, and comes from trying too hard to apply power immediately at the start of the downswing. If one wants a big slice, this is the way to get it.
Swinging on or below the plane results in powerful shots that fly straight or have a slight draw. This is highly desirable.
I have to focus on keeping my swing flat (more like a merry-go-round, less like a ferris wheel) with longer clubs. I always have. I have a tendancy to cast with driver if I don't swing low and slow enough. Interestingly, this is the same focus John Daly reports for his driver swing thought: low and slow.