There are a few simple facts derived from physics that can help explain some of the things that we do — or should do — in the golf swing. For example, the more you can contact the middle of the ball in the middle of the clubhead, the greater will be distance and accuracy.
When the centers (or more accurately the centers of gravity) of both club and ball are lined up at impact, you will able to impart the greatest force to the ball so that it will carry the greatest distance. If the centers do not line up and are off even by 1/16th of an inch, it can equate to a 10 to 20 yard loss in distance on your drive.
This is one of the reasons why practice, especially perfect practice, is so important to achieve this goal for accuracy in the hit. In other words, you must hit hundreds, if not thousands, of the balls before you can reproduce a perfect swing on every attempt. But even on the highest levels of performance we see how this is extremely difficult to accomplish. But the more you can practice, the more ingrained this swing will be to ensure accuracy on most of the hits.
If the centers of gravity of the ball and clubhead are not lined up at contact, there is a tendency for the clubhead to turn in the direction of the off hit. For example, if you hit more off the toe, the clubhead will have a tendency to rotate clockwise through the center of the clubhead (or shaft) when viewed from the top. This is why you may feel the club shaft trying to turn during the hit. It is also why a tight grip at the moment of impact is needed. It will help prevent rotation of the clubhead and insure a straighter hit.
Thus it is possible to see how important it is that you have the physical abilities not only to execute the swing, but also to ensure that there’ll be no turning of the clubhead during contact. The strength of the finger and hand muscles is especially important here. Note that this recommendation is also contrary to what many pros advocate, i.e., that you should have a relaxed grip throughout the swing. This holds true only up to the final portion of the swing when you must make contact.
See Explosive Golf for more information on strengthening the muscles specific to the golf swing and exercises specific to strengthening of finger and hand muscles as they are involved in the swing and especially at contact.