The representative techniques of MMT presented here are based on the work of a number of investigators. No attempt will be made to present all the tests devised for any particular muscle. Instead, nine important parameters of the MMT procedure that should be followed when testing any muscle will be presented in order to attain reliability and validity with this diagnostic tool.

1. Is the test used a standardized MMT of the muscle or group of muscles, or is it a general test such as 'the arm test'?

2. On how many muscles is the procedure valid?

3. Are the starting point and the direction of force the same each time the muscle is tested?

4. Does the tester apply the same force with the same timing each time the muscle is tested, i.e. does the tester apply the force to the patient at a constant rate and speed?

5. Is the contact point on the patient the same each time the muscle is tested?

6. Is the tester's hand contact with the patient the same each time the muscle is tested?

7. Are the tester's elbow, arm and forearm in the same position for each test?

8. Are the tester's shoulders relaxed and in the same plane each time the muscle is tested?

9. Is the tester's body in the same position with the core muscles of his body engaged in the same way each time he tests the muscle?

An explanation for each of these clinical guidelines follows:

1. Is the test used a standardized MMT of the muscle or group of muscles, or is it a general test such as 'the arm test'?

Much error in muscle testing is a result of testing a general group of muscles rather than a specific muscle. General tests such as "the arm test" are actually, at best, testing a gait function, a series of muscles, rather than a specific muscle. The type of response gathered from the MMT depends on the type of MMT employed, and "the arm test" gives a different response than do the standardized tests of specific muscles.

The standard references for muscle testing evaluation as accepted by the I.C.A.K. are the original work of Kendall and Kendall, Muscles: Testing and Function [12], and the modifications suggested by Goodheart in his Applied Kinesiology Research Manuals [1]. Goodheart's and the I.C.A.K.'s investigations into the use of the MMT for chiropractic diagnosis have been well organized and disseminated to the professions by Walther and others [7, 15, 16, 76–78].

It is critical that the MMT protocol be highly reproducible by the examiner and by others. The earliest books on the use of the MMT for the functional assessment of patients argue that appropriate methodological techniques must be strictly followed before obtaining or interpreting MMT outcomes [1, 10–13]. This call still echoes among the numerous abuses that have been promulgated throughout the past 40 years of MMT use in the manipulative professions [18–25, 27].

An understanding of the principles in the original works of Kendall, Goodheart, and Walther is necessary for using the MMT. The testing procedures from these volumes may be modified slightly, depending on the structure of the patient, but must be consistent from test to test on the same individual. Observe the difference between the two tests shown in Figures 1 and 2. Figure 1 shows "the arm test" while Figure 2 shows the middle deltoid MMT. "The arm test" monitors all the arm flexors and abductors as a group, and the middle deltoid isolates a specific muscle and evaluates the neurological functions thereby identified. In figure 1 the patient's head is also turned and she is leaning her torso onto her left hip. Figure 3 shows that the MMT is not a contest between the patient and the doctor.

Figure 1 The "arm test" does not isolate nor specifically test any particular shoulder muscle. Full size image

Figure 2 Middle deltoid MMT. Full size image

Figure 3 The MMT is not a competition between the examiner and the patient. Full size image

It should be observed that a relationship between shoulder pain and dysfunction and specific muscle weakness has been established in a number of studies [79–84].

The MMT should evaluate individual muscles as far as possible. There is an overlap of muscle actions, as well as an interdependence of muscles in movement. This close relationship in muscle function need not rule out the possibility or the practicability of testing individual muscles. There is an ideal starting position and vector of testing force that places the muscle being tested as the prime mover and the synergists at a disadvantage during the test.

Janda (who also used the MMT to evaluate locomotor dysfunction) has emphasized that prime movers and synergists are tested with the MMT, not individual muscles [63]. However, it should be pointed out that every muscle is a prime mover in some specific action. In the search for that action, one is led into the field of precise, individual muscle testing. Manual muscle tests are designed to replicate the primary vector of motion of a muscle while minimizing the contribution of secondary mover muscles. During an individual MMT, the designated primary mover muscle should have the highest level of activity compared with the secondary mover or synergist muscles. When any one muscle in the body is inhibited in its strength or action, stability of the part is impaired or some exact movement is lost to some extent. When inhibition of a muscle results in the inability to hold the test position or perform the test movement ascribed to that muscle, the validity of the individual muscle test is substantiated (Figure 4).

Figure 4 MMT of the psoas major muscle. It shows that the quadriceps, sartorius, and adductor muscles all assist in holding the hip in a flexion position. However, the line of pull of the muscle and the direction of the examiner's pressure place emphasis on the action of the right psoas major, making identification of inhibition in this specific muscle possible. Full size image

2. On how many muscles is the procedure valid?

The Research Committee of the I.C.A.K. has adopted a policy wherein any new diagnostic or manipulative treatment technique must be evaluated using three separate and distinct muscles, one of which is the quadriceps femoris tested in the supine position (Figure 5), before it is considered reproducible and valid. Many times we see a technique or research paper presented using "the arm test" (which is easily misperformed or misinterpreted) that cannot be reproduced when applied to another muscle, especially the large and powerful quadriceps femoris muscle [18, 20, 21].

Figure 5 Quadriceps femoris MMT. Full size image

It should be observed that a relationship between knee pain and dysfunction and muscle weakness has been identified in a number of studies as well [38–40, 84–88].

3. Are the starting point and the direction of force the same each time the muscle is tested?

The enthusiasm for a new idea has many times blinded the tester from realizing that he alters the starting position of the test and his line of force. From one test to the next this may vary as much as several inches or 45 degrees, thereby invalidating the data he receives from the test. The starting point should be consistent. The line of force should not vary more than a few degrees from test to test. Failure to strictly follow these guidelines leads to substitution of synergistic muscle function replacing or supplanting the muscle that is being examined, thereby altering the parameter being examined (Figures 6 and 7).

Figure 6 Hamstring MMT. Full size image

Figure 7 Hamstring MMT incorrectly done. Knee excessively flexed allows muscles to cramp and makes the test difficult to judge. Full size image

Poor motor control – as demonstrated by synergist substitution that must be carefully monitored and prevented during the MMT – has been linked to decreased joint stability [48, 89, 90]. As mentioned previously, Lund hypothesizes that when pain is present, there is decreased activation of muscles during movements in which they act as agonists and increased activation during movements in which they are antagonists. Rather it appears that muscle imbalance is the rule in injuries, pain, and inflammation, with certain muscles tending toward inhibition and others toward hyperactivity. This explanation is more in line with the common impression that pain makes muscles difficult to use and less powerful [91].

Synergist substitution may be the body's attempt to compensate for an inhibited muscle that is not adequately stabilizing a joint. Edgerton reports that synergist substitution for inhibited muscles distinguished chronic neck pain patients from asymptomatic patients after whiplash injury [48]. In these patients, overall muscle strength may not be inhibited if tested with a dynamometer because synergists substitute for the specific inhibited agonist muscles that should be identified by precise positioning during the MMT.

For accurate MMT examination, no substitutions should be permitted. The position or movement described as the MMT should be done without shifting the body or turning the part to allow other muscles to substitute for the weak muscle. It is natural for the subject to change the MMT parameters to recruit synergistic muscles in the presence of a weak prime mover. Accurate MMT depends upon the examiner's awareness of this factor and the ability to detect it when it occurs. Because synergist-agonist substitution for inhibited muscles is so common in neuromusculoskeletal dysfunction [65, 66]. the importance of specific (not group) MMT is once again apparent.

Synergist substitution is frequently seen in impairments of gluteus maximus function on the MMT [2, 15, 59, 66]. It should also be observed that a relationship between low-back dysfunction and pain and specific muscle weakness in the gluteus maximus muscle has been established in a number of studies (Figures 8, 9 and 10) [43, 90, 92].

Figure 8 Gluteus Maximus MMT. Full size image

Figure 9 Gluteus Maximus test incorrectly done: excessive extension. Patient tends to straighten leg to recruit more hamstring synergism. Knee flexion helps eliminate the hamstring's contribution to the test. Full size image

Figure 10 Synergist substitution can be identified and prevented during the MMT. With a weak gluteus maximus, the examiner can visualize a lifting of the pelvis with external rotation and abduction of the hip, with recruitment of the ipsilateral hamstring, thoracolumbar extensors, and contralateral leg flexor muscles. The pelvis externally rotates because the weak gluteus maximus recruits synergists to facilitate its action during the MMT. Full size image

4. Does the tester apply the force to the patient at a constant rate, i.e. does the tester apply the same force each time the muscle is tested?

It is easy to overpower even the strongest patient if you apply force too rapidly or "jump the gun" as it is often referred to. Muscle testing evaluates the strength of response of the muscle, not the speed of response. Muscle testing is an art in which the force applied to the patient is increased at a constant rate until the tester senses the muscle begin to give way. The classic "break test" used by physical therapists tests this phenomenon as well [11–13]. Clinically this is then compared with the amount of force needed to cause the muscle to begin to give way following the application of a variety of treatment and assessment procedures, and the tester must accurately monitor whether or not there is a difference.

In presenting MMT and AK methods to an audience, many of these subtleties are not easily conveyed. This leads the lecturer to test the muscle through its entire range of motion in order to bring the point across to the audience. It is not, however, the recommended practice for clinical use. As Walther states, "Once the muscle is in motion, the test is over" [15]. The amount of force required to initiate motion is the parameter that should be measured in accurate MMT. Overpowering a muscle can be noted when the tester applies the force too rapidly or forces the muscle through its entire range of motion before determining its ability to resist.

A previous literature review in this journal [93] as well as other research reports has shown the importance of clinical experience and expertise concerning the reliability of the MMT [11–13]. The skills of the examiners conducting studies on MMT and their skills in interpreting the derived information will affect the usefulness of MMT data. Examiners are obliged to follow standardized protocols that specify examiner and patient position, the precise alignment of the muscle being tested, the direction of the resisting force applied to the patient, and the verbal instruction or demonstration to the patient.

An experienced examiner who is aware of the ease with which normal muscles perform the MMT will readily detect substitutions if there is weakness. Even an inexperienced examiner can often detect the sudden shift of the body that results from the effort to compensate for muscle weakness during the MMT.

Mendell and Florence (1990) [94], Caruso and Leisman (2000) [95], and other researchers of MMT have discussed the importance of considering the examiner's training for the interpretation of studies that assess strength via MMT.

From these studies it appears obvious that training and skill are necessary to perform these tests properly and to interpret their outcomes reliably. MMT for functional neuromusculoskeletal evaluation is more sophisticated than simply asking the patient to shrug the shoulders to ascertain if cranial nerve XI is intact. When conducted properly the procedures have reported significant inter- and intra-examiner reliability as well as significant construct, content, concurrent and predictive validity [93].

5. Is the contact point on the patient the same each time the muscle is tested?

The point of contact between the tester and the patient can be a critical factor for two reasons. First, the amount of leverage the tester has at his advantage can alter the performance of the test. The contact point of the tester's hand on the patient should not vary more than 1/2 inch from test to test.

Second, many areas of the body are extremely sensitive to pressure; thus a patient's muscle may yield not to the force put on it, but to the pain from the tester's contact point. This is especially true of the wrist and ankle, where the bone is very sensitive and not adequately padded by soft tissue.

Many tests also require that the tester provide stabilization for the patient with the hand other than the testing hand. The stabilization hand should be placed in the same position every time the muscle is tested. It is very easy for the over-enthusiastic tester to properly stabilize the patient on one test and to unknowingly allow the previously stabilized body part to move on subsequent tests. In the case of normally strong pectoralis major (sternal division), or psoas major muscles, lack of proper stabilization may cause the muscles to appear weak because the patient allows them to give way when he feels his body beginning to fall off the table. The tested muscle must always be functioning from a stable base during MMT. Care must also be taken to ensure that the position of the stabilizing hand on the patient does not cause pain, which would again cause him to release his resistance (Figures 11 and 12).

Figure 11 Pectoralis major muscle (sternal division), proper hand contact. Full size image

Figure 12 Hand position changed, painful contact on bony prominence. Full size image

6. Is the tester's hand contact with the patient the same each time the muscle is tested?

This is a very important and often overlooked criterion. Notice the difference between the part of the hand with which the tester applies pressure in Figures 13 and 14. Proper muscle testing involves the sensitivity of touch-pressure and joint receptors in the examiner's fingers and hands. Proper discrimination in the amount of force applied must be monitored by the examiner's fingers. Hence the examiner must keep his awareness primarily centered on the amount of pressure he senses through his fingers, and to a lesser extent, his wrist, elbow and shoulders. The MMT with the fingers on one test and then with the palm on another test will cause one to interpret the finger test as stronger than the palm test since the brain receives more impulses from the rich endowment of nerve endings of the fingers, regardless of the actual force exerted. An examiner who is not cognizant of this fact may inadvertently change the area of his hand that contacts the patient from test to test, and his brain will interpret and process the disparate information which it receives. This is a critical area that allows many examiners to deceive themselves, only to become embarrassed at a later date when they discover what they are actually doing.

Figure 13 Hand contact – fingertips. Full size image

Figure 14 Hand contact – full palm. Full size image

7. Are the tester's elbow, arm and forearm in the same position for each test?

Note the difference in the examiner's elbow, arm and forearm positions in Figures 2 and 15. One can readily see the difference in leverage the examiner exerts at each position. Note in Figure 15 that the examiner has a tendency to push down with the weight of his arm (and possibly his whole body) rather than exert pressure through his fingers as discussed above (and shown in Figure 2). Also notice in Figure 15 that the examiner has the tendency to try to force his entire body weight on the patient's arm, thus overpowering her. These errors in testing are sometimes due to the disparity in height between the examiner and patient. In both cases, the examiner has the tendency to judge the amount of pressure he exerts not by the finger receptors as discussed above, but by the wrist, elbow, and shoulder proprioceptors. This method yields inconsistent and therefore invalid results. The arm, forearm and elbow positions should be the same each time the test is performed. Kendall, Walther, and others have extensively described the clinical guidelines for doctor and patient positioning during the MMT for each muscle, and this training is available through several of the chiropractic colleges and the I.C.A.K [1, 12, 13, 15, 96].

Figure 15 Middle deltoid MMT – mechanical advantage. Full size image

8. Are the tester's shoulders relaxed and in the same plane each time the muscle is tested?

Compare the level of the shoulders in Figures 2 and 15. Figure 4 shows the psoas major MMT being performed properly. Figure 16 shows the examiner leaning over the patient and inadvertently transferring his entire body weight to the patient's leg. This is a very common error observed in undertrained muscle testers.

Figure 16 MMT of the psoas major muscle-mechanical advantage. Full size image

9. Is the tester's body in the same position with the core muscles of his body engaged in the same way each time he tests the muscle?

This error in muscle testing, most often associated with "the arm test", involves the examiner literally leaning his entire body weight on the patient. This is demonstrated by the difference between Figures 2 (normal) and 15 (leaning) and Figures 17 (normal) and 18 (leaning). This mistake can be avoided if the examiner places his feet and his umbilicus in the same position each time he tests the patient.

Figure 17 Tensor fascia lata MMT. Full size image