Consideraciones generales

• If the patient can perform the test against manual resis- tance, a grade of greater than 3 is assigned depending on the magnitude of the resistance applied.

The patient is asked to relax at the end of each test movement and the therapist positions the limb for the next test movement.

Manual Resistance

To apply resistance, use a lumbrical grip, in which the metacarpophalangeal joints are fl exed with the interpha-

langeal joints held in extension and the thumb either adducted or relaxed in slight extension ( Fig. 1-68 ). Add resistance gradually to allow the patient to “set” the muscles. Apply the resistance force at a 90 ° angle to the limb segment.

Apply the resistance force at the distal end of the seg- ment into which the muscle(s) being tested is (are) inserted 11 , 85 _{( Fig. 1-69 ). Allowing a joint to come between} the point of application of the resistance and the muscle insertion may increase the chance of substitution. Ensure resistance is not given distal to an unstable or weakly sup- ported joint. Every attempt should be made to keep the length of the resistance arm (i.e., the distance between the axis of rotation of the joint and the point of application of the manual resistance) standard for each muscle test. Note: The longer the length of the resistance arm, the less the resistance force required to counteract the torque produced by the muscle.

Nicholas and coworkers 123 _{report that if the therapist} gives an equal or greater resistance to the limb when test- ing muscle A but for a shorter period of time than when testing muscle B, it is possible that muscle A could be assessed as being weaker than muscle B. When applying resistance to test a muscle, the therapist mentally inte- grates the time taken to go through the ROM with the magnitude of the resistance force to arrive at a perception of the strength defi cit and assign a grade. 123 _{Because of} this and the force-velocity relationships, when perform- ing comparable muscle tests, apply resistance over the same length of time, and if assessing muscle strength

Figure 1-66 A. Manual muscle testing (MMT) start position against gravity: elbow extensors – triceps. B. Patient attempts to perform elbow extension against gravity. If a grade of 2 + or 3 − is assigned, the MMT stops. If a grade 3 is assigned, repeat the test and apply manual resistance ( Fig. 1-67 ). If unable to move against gravity, reposition the patient and test the movement gravity eliminated ( Fig. 1-70 ).

through range, use the same velocity of movement to go through the ROM.

Resistance Applied to Test Strength “Through Range” . When assessing muscle strength using concentric muscle con- traction, the magnitude of the resistance force is based on the amount of resistance that can be applied and allow the patient to move smoothly through the full

ROM. The resistance force applied throughout the movement “should be just a little less than would stop the movement.” 87(p. 568) _{Modify the amount of resistance} given throughout the ROM according to the patient’s capabilities. If too much resistance is given, the patient will not be able to move through the ROM and this may lead to recruitment of other muscles to perform the movement.

B

Figure 1-67 MMT elbow extensors – triceps. A. With the patient positioned against gravity apply manual resistance either through range, or isometrically, and grade the strength. B. Manual resistance is applied at the distal end of the segment the muscle inserts into, that is, the distal end of the radius and ulna.

Figure 1-68 Manual resistance applied at a 90 ° angle to the limb segment using a lumbrical grip.

Figure 1-69 Apply manual resistance at the distal end of the segment the muscle(s) inserts into.

Testing strength through range requires considerable skill and experience. 85 _{For this reason, the results of} testing strength through range may not be as certain as when performing MMT using isometric muscle contrac- tion in selected part(s) of the ROM, 85 _{as is more com-} monly practiced now. This being said, it behooves the therapist to acquire the skill and experience to compe- tently test strength through range. The most appropriate means of testing strength, either through range or at a selected joint position(s), is used based on the specifi c clinical requirement.

It may be advantageous to test muscle strength through range, for example, “to obtain a more specifi c clinical picture of a peripheral nerve lesion and its course of motor recovery”. 103(p. 666) _{When grading muscle} strength, the ability of the patient to move through part or all of the ROM is more easily quantifi ed than changes in the magnitude of the applied manual resistance. 96

Resistance Applied to Test Strength “Isometrically” At Specific Joint Angles. When using isometric muscle con- tractions to test muscle strength, the strength needed to hold the test position is considered to be the same as the relative strength needed to move through the test move- ment, 11 _{although Wilson and Murphy} 124 _{note, there is no} research to suggest that force measured at any one point in the ROM is representative of muscle force throughout the entire movement. Strength varies throughout the ROM and a more accurate picture of the muscle’s capa- bilities is attained if isometric muscle tests are performed with the muscle positioned in inner, middle, and outer ranges or better yet, the muscle test is performed through the ROM.

Koo and coworkers 125 _{studied the elbow muscle weak-} ness of hemiplegic subjects using isometric testing. The study fi ndings support the need to evaluate isometric muscle strength in multiple joint positions throughout range to provide a complete assessment of muscle weak- ness from a clinical and functional perspective.

To maintain reliability in testing when using isomet- ric muscle contraction, the muscle should be tested in the same part(s) of the ROM each time. 86 _{Isometric test-} ing is an accepted clinical method of assessing muscle strength, 126 _{but predicting dynamic work capabilities} from isometric tests is generally not reliable. 69 , 124 Dynamic tests are superior to isometric tests in their relationship to dynamic activities. 124 _{It would be more} appropriate to test a muscle or muscle group taking its normal function into account; that is, using isometric testing for muscles that function as stabilizers, such as the scapular muscles.

When using isometric contraction to grade muscle strength that is greater than a grade 3, the therapist posi- tions the limb segment so the muscle will contract in either outer, middle, or inner range against gravity and then grad- ually takes away any support as the patient attempts to hold the position. Alternatively, the patient actively moves the limb segment into outer, middle, or inner range for the muscle being assessed. The position illustrated for most muscle tests in this textbook is inner range, as this position is often the weakest part of the range.

If the limb segment is held in the start position against gravity, the therapist gradually applies resistance and per- forms either of the following:

• Make test 127 _{in which the resistance must not “break”} the muscle contraction so that the patient cannot hold the position.

• Break test in which the therapist gradually decreases the resistance as the limb segment is felt to fall toward the muscle’s outer range. If the strength is considered to be a grade 5 or normal, the make test is used, and no effort is made to break the subject’s hold. 11

The break test is the most commonly used technique. Using either test method, the therapist has the patient maintain the contraction for about 4 seconds to allow time to establish a maximal isometric contraction. 128 The muscle is graded based on the maximal amount of resistance the muscle can hold against. The break test technique produces greater strength measurements than the make test technique. 129 _{To maintain reliability in} testing, use the same test technique (i.e., make or break test) on subsequent testing, and record the technique used.

To assess strength if joint movement causes pain and no contraindications exist, it is extremely diffi cult if not impossible to perform a static contraction and produce a situation where absolutely no movement occurs at the joint crossed by the muscle. There is always some degree of joint movement, compression, and shearing even with static muscle contraction. 130 _{However, it may be possible} to perform a pain-free isometric muscle test with the joint placed in the loose-packed (resting) position. Keep one hand immediately below the patient’s limb so that no movement or only slight movement occurs if the patient is unable to hold the limb in any part of the ROM against