Human body is composed of bones linked by joints to form the skeleton. The skeleton is covered by soft tissues like organs and muscles. There are three body planes in which movement of each joint can be defined. They are: (1) sagittal or lateral plane that divides the body into right and left planes, (2) transversal or horizontal plane that divides the body into upper and lower parts, and (3) frontal or coronal plane that divides the body into anterior and posterior parts. Figure 2 (right) [24] depicts human body planes. Movement in the sagittal plane is called flexion and extension. Flexion is a movement that reduces the angle between bones or part of the body, and extension is a movement that increases the angle between the bones of the limb at a joint. Movement in the coronal plane is called abduction and adduction. Abduction is an outward movement of the limb away from the median plane of the body and adduction is a movement that brings a limb closer to the body in the sagittal plane. Another movement is pronation and supination. Supination is rotation of the forearm so that the palm position is anterior, i.e. the palm facing up and pronation is rotation of the forearm that moves the arm from an anterior-facing position to a posterior-facing position, i.e. the
palm facing down. Rotation is the movement of a joint around the long axis of the limb in a circular motion. Rotation can be either internal or external. Another movement is circumduction. The circumduction is a circular movement in which flexion, abduction, extension and adduction are combined in a sequence. The most commonly used example is shoulder joint. Figure 2 (left) [26] depicts human arm movements.