The Biomechanics of Motion

For a martial arts student to develop skill and confidence in self-defense techniques, it is helpful to understand concepts of biomechanics or the study of how the body moves. Biomechanics is important in being able to control an opponent with minimal force, as well as protecting your training partner from injury. Such techniques are available in books, but to truly understand their use and precision requires professional instruction by qualified teachers.

Techniques learned at Christopher N. Geary's Shaolin Kempo include components of Shaolin Chin Na, which is the use of joint locking techniques to protect yourself but controlling your opponent efficiently. This often is combined with redirection of a limb to produce the desired control.

Anatomy
Joints are areas of the body where 2 or more bones meet to allow the body to move. They are held together by joint capsules and ligaments which allow only a certain range of motion. This range is different from person to person, thus stressing the need to workout with many different training partners to appreciate differences in joint motion. Cartilage typically lines the touching surfaces of the bones allowing smooth movement. Tendons which cross the joints are pulled by muscle contractions, which cause the joint to be moved or stabilized. Joints are also surrounded by soft tissues (subcutaneous fat, skin, nerves and blood vessels) that act to limit joint motion.

Biomechanics
Joint motion can occur in different directions depending on the joint considered. As an example, fingers bend and to a lesser degree they extend, but the thumb moves in many more angles. The following describes joint motion:

Flexion: Bending or shortening the angle between the bones of a joint.
Extension: Motion that pulls bones into a straight alignment.
Abduction: Motion that brings a body part away from the midline of the body.
Adduction: Motion that brings a body part towards the midline of the body.
Opposition: Motion that brings a body part close to or touching another body part.
External rotation: Motion that rotates a body part outward.
Internal rotation: Motion that rotates a body part inward.
Plantar flexion: Motion of the foot downward toward the ground.
Dorsiflexion: Motion of the foot upwards toward the shin.
Circumduction: Motion produced in a circular fashion.