ABSTRACT
Understanding lever systems is essential to know how force is applied to the movements of the body. Levers in human anatomy are basically comprised of bones that rotate around a fixed point called a fulcrum or axis. Baseball bats, golf sticks, tennis rackets, swords, and other sports instruments represent "artificial extensions of the resistance arms" of body levers, which increase the speed at the striking point but require an increased muscular force. Muscular tonus is a state of partial contraction that is characteristic of normal muscle; it is maintained at least in part by a continuous bombardment of motor impulses originating reflexively, and serves to sustain body posture. Static activity is strictly associated with body balance or equilibrium. In dynamic activity, there are three types of motion: rectilinear, rotary, and curvilinear. Rectilinear motion happens when a body moves and its parts travel exactly the same distance in the same direction and in the same time.
