The more flexible the shaft the more the golfer realizes the feel of a solid impact. Conversely, the more stiff the shaft the less solid the feeling of impact will be. The increased bending, loading and unloading of the shaft just prior to impact is what creates the sensation of the impact being more solid.
Most adult males play shafts that are ill-fitting.
Usually, too stiff. Stiff shafts require a pretty crisp swing speed. Extra stiff shafts are used by those who have monster swings or who are very athletic. Click here for help choosing the proper shaft flex. Stand comfortably erect, shoulders perfectly level and arms hanging comfortably at the sides.