In order to execute each phase of the golf swing correctly certain levels of flexibility, balance, strength, endurance, and power are required. If a golfer is lacking in any one of these physical parameters required of the golf swing. Compensations will occur within it. Not from the actual biomechanics of the swing, but rather from the body.
For example, if you are lacking the proper levels of flexibility to perform a full shoulder turn. Compensations will occur in the golf swing directly related to this lack of flexibility in the body. Often the amateur fails to realize the compensation is a result of their body and fails to ever "fix" or improve their golf swing as a result. Bottom line, the golf swing requires certain levels of flexibility, balance, strength, endurance, and power to execute correctly. If the amateur desires to improve their golf game some attention must be focused upon developing these parameters within the body.
The development of these physical components for the swing can be achieved through the implementation of a golf fitness program. Such a program will develop the requirements of the body relative to the swing. Allowing you the ability to execute the golf swing correctly.