On the nomenclature of skeletal muscles The individual muscles of the axial and limb portions of the body are named according to their action, structure, shape, and other characteristics, for example, semimembranous, semitendinous, deltoid, flexor, and extensor. A group of muscles having a common function is usually named in accordance with the kind of motion produced by it. Thus groups of muscles which normally decrease or increase the angle of position of the levers (bones) related to the joints and more rigidly fixed parts are called flexors and extensors, respectively. In running, the extensors and flexors of the legs, thighs, and arms are employed alternately within the same limb and reciprocally in the opposite limb. Muscles which move a part or member away from the line of the vertical axis of the body are known as abductors; those which move a part toward this axis are known as adductors. Others which rotate the bones relative to the point of attachment are called rotators and are found in association with ball-and-socket joints. In the various forms of exercise commonly engaged in by man, all of these types of action are usually involved. The nicety of coördination between the various muscles of the axial and appendicular groups acting upon the framework of the skeletal system enables the individual to assume certain postures. Of these we may mention those of standing, sitting, reclining, and kneeling. In a similar manner, movements of locomotion such as walking, running, jumping, swimming, and dancing are dependent on well-timed and coördinated contractions and relaxations of the muscles involved.		Home Classes of levers Varieties of muscle Smooth muscle The blood supply to muscles The neurone Cardiac muscle On the nomenclature of skeletal muscles The nerve supply to muscles Structure of a skeletal muscle Central nervous system The reflex arc and reflex action Physiologic properties of muscle Mechanical Changes The effects of temperature on muscular contraction Muscle glycogen, its source and fate The reaction of muscles Oxygen consumption of muscle Determination of the oxygen consumption of muscle The viscosity factor in muscle and muscle efficiency Significance of the recovery heat Production of Electricity