Amateur golfers often make the mistake of gripping the golf club very tightly in anticipation of a powerful swing. Legendary teaching professional Harvey Penick believed this was wrong and caused numerous errors in the golf swing. A tight grip will tense muscles in the arms and restrict motion in the swing.
Penick suggested holding the club as if holding an antique violin. Renowned PGA teaching professional Mitchell Spearman recommended holding the club as if holding a tube of toothpaste. The grip pressure should be just tight enough to barely squeeze some paste out of the tip. A relaxed grip on the club will lead to relaxed arms and shoulders, and will help promote a full shoulder turn. A tense grip will restrict this motion and limit driving distance.
Several grip styles exist, but the most common grip is the "Vardon" grip, named after six-time British Open winner Harry Vardon. This grip involves wrapping the right hand over the left thumb, with the right pinkie either overlapping the left index finger or interlocking underneath it. Ben Hogan believed that for a right-handed golfer, the thumb and forefinger of the right hand are detrimental to the swing and should be practically released from the club during the swing. Tiger Woods also believed that grip pressure should be controlled with the left hand.
Driving distance is a combination of the angle of attack at impact and clubhead speed. The club should attack the ball at a sharp angle, with a lot of lag created between the hands and the clubhead. Because the swing works in a pendulum-like manner, a wider swing arc will produce more distance. A tense grip will cause a narrow and shallow swing arc and prevent this lag from occurring.
Another factor that contributes to distance is the hinging of the wrists at the top of the swing. Spearman refers to this as the "wrist cock," and PGA professionals use this to create lag between the hands and the club. At the top of the back swing, the wrists should be allowed to hinge, creating one last increase in the swing arc. This allows the club to return at a very sharp angle and produce maximum compression on the ball. A tense grip will restrict the wrists from hinging freely.
A Test for Measuring Grip Pressure
A simple test for determining grip pressure, according to Spearman, is to first grip the driver as normal. Hold the club out in front of you and apply the same pressure you would as if you were going to drive a golf ball. Have a friend try to twist the clubhead. If the club slips in your hands, your grip isn't tight enough. If the friend can't move the club at all, your grip is too tight.