Muscle testing depends on a thorough understanding of which muscles are used in performing certain movements. Testing is best performed when the patient is rested, comfortable, attentive, and relaxed.
Prior to testing strength, the examiner should assess muscle bulk (is there muscle atrophy, or hypertrophy and, if so, which muscles are affected?). The examiner should also note fasciculations, if present, and should record the specific muscles in which they are present.
Because several muscles may function similarly, it is not always easy for the patient to contract a single muscle on request. Positioning or fixation of parts can emphasize the contraction of a particular muscle while other muscles of similar function are inhibited. The effect of gravity must be considered because it can enhance or reduce certain movements. Testing of individual muscles is useful for evaluating peripheral nerve and muscle function and dysfunction. The normal or least affected muscles should be tested first to gain the cooperation and confidence of the patient. The strength of the muscle tested should always be compared with that of its contralateral muscle.
The strength of various muscles should also be graded and charted. Scales of various types are used, most commonly grading strength from 0 (no muscle contraction) to 5 (normal).
See Tables B–1 and B–2 and Figures B–1 to B–52. Notice that in all the figures, blue arrows indicate the direction of movement in testing the given muscle. Black arrows indicate the direction of resistance, and the blocks show the site of application of resistance.
TABLE B–1Grading Muscle Strength. ||Download (.pdf) TABLE B–1 Grading Muscle Strength.
|No muscular contraction
|A flicker of contraction, either seen or palpated, but insufficient to move joint
|Muscular contraction sufficient to move joint horizontally but not against the force of gravity
|Muscular contraction sufficient to maintain a position against the force of gravity
|Muscular contraction sufficient to resist the force of gravity plus additional force
|Normal motor power
TABLE B–2Motor Function. ||Download (.pdf) TABLE B–2 Motor Function.
|Action to Be Tested
|Shoulder Girdle and Upper Extremity
Flexion of neck
Extension of neck
Rotation of neck
Lateral bending of neck
|Deep neck muscles (sterno-cleidomastoid and trapezius also participate)
Elevation of upper thorax
|Adduction of arm from behind to front
|Pectoralis major and minor
|Pectoral (thoracic; from medial and lateral cords of plexus)
|Forward thrust of shoulder
Elevation of scapula
Medial adduction and elevation of scapula
Abduction of arm
Lateral rotation of arm