Flexibility is something that people often lose with age (as the woman in the photo, back right). But loss of flexibility is more closely associated with inactivity than with age. In other words, if you don't use it, you lose it. Someone who is flexible can move their joints through their entire intended range of motion. Lack of flexibility can negatively effect your performance in many ways. Poor flexibility creates extra effort when performing many common tasks. Poor flexibility also negatively effects your performance in recreational activities such as tennis or golf. Proper stroke mechanics require good flexibility. Flexibility facilitates efficient stroke mechanics which adds to ones skill level, thereby enhancing enjoyment of the activity.