Now more than ever people use their mouse more than typing on the keyboard. Invariably, prolonged use of the mouse  will add undue stress to the body, particularly the fingers, hand, wrist, arm, shoulder, and neck. Of these stresses, overreaching for the mouse is one of the biggest culprits, because it requires you to exert your arm muscles over a greater distance than, say, using your fingers while typing. The further the reach, the greater the potential for injury.

Central pointing devices have been gaining exponential popularity due to the fact that you mouse inline with your body and machine.