MANUAL MUSCLE EXAMINATION Manual muscle testing is a procedure for the evaluation of the function and strength of individual muscles and muscle groups based on effective performance of limb movement in relation to the forces of gravity and manual resistance. Maximum muscular strength is the maximum amount of tension or force that a muscle or muscle group can voluntarily exert in one maximal effort, when the type of muscle contraction, limb velocity, and joint angle are specified. We will only be concerned with two types of muscle contractions for this type of examination: isometric (static) and concentric. Other types of muscle contractions to learn and to incorporate into the testing of athletes are: isotonic, isokinetic, and eccentric. Isometric contractions occurs when there is tension developed within the muscle but no movement occurs. The two insertion sites do not change positions, and the muscle length does not change. Concentric contractions develop tension within the muscle, the two insertion sites move closer together, and the muscle shortens. Some muscles will cross two or more joints. When those muscles produce simultaneous movement at all of the joints it crosses, the muscle will reach such a shortened position that it no longer has the ability to develop effective tension. This is called Active Insufficiency. Three functional classifications of muscles will be used with Manual Muscle Testing: prime mover or agonist, antagonist, and synergist. The agonist muscle or muscle group makes the major contribution to movement at a joint. Antagonist muscles have an opposite action to the agonists. To some degree, the antagoist muscle relaxes as the agonist moves through part of the ROM. Synergists are muscles that work along with agonists to produce the desired movement. They can work in three characteristic ways: as neutralizing or counteracting synergists (prevent unwanted movements), conjoint synergists (work together to produce the desired movement), or stabilizing or fixating synergists (stabilize proximal joint movement). Many factors will affect strength: age, type of contraction, muscle size, speed of contraction, training effect, joint position, and fatigue. Other factors such as nutrition, level of motivation, pain, body type, sport, and limb dominance will not be considered here. As age increases through about age 28, strength may increase, but as age increases from there strength usually decreases due to a decrease in fiber size and number, an increase in connective tissue an fat as replacement, a decrease in energy capacity of the muscle. More tension can be generated through eccentric contractions than isometric, and concentric contraction produce the least tension. Generally, the larger the cross-sectional area of a muscle the greater the strength. For concentric contractions, contraction forces decrease as the speed of contraction increases. The opposite is true for eccentric contractions. Strength can be seen to increase as the athlete becomes familiar with and learns the test situation. The turning effect about a joint that is produced by contraction of muscle is called the moment of force or torque. Torque can be measured as the product of the muscle force and the perpendicular distance between the joint axis of rotation and the muscle force. The optimal angle for the muscle to produce peak torque is at an angle of 90 degrees to the moving shaft. At greater or lesser angles, there are greater or lesser stabilizing, compressing, and distracting forces applied at the joint. Regardless of the type of muscle contraction, a muscle contracts with more force when it is stretched than when it is shortened. The angle of muscle pull and the length-tension relation interact to produce the
muscle force curve. When testing isometrically at several angles, most muscles will have a decrease in strength the stretch and beginning ranges to the shortened and ending ranges. As the athlete fatigues, muscle strength...
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