On the reliability and validity of manual muscle testing: a literature review

Scott C Cuthbert 1, George J Goodheart Jr 2

1-Chiropractic Health Center, 255 West Abriendo Avenue, Pueblo, CO 81004, USA

2-Goodheart Zatkin Hack and Associates, 20567 Mack Avenue, Grosse Pointe Woods, MI 48236-1655, USA

In this review, Cuthbert and Goodheart use the International College of Applied Kinesiology’s (ICAK) definition of the MMT:

“Within the chiropractic profession, the ICAK has established an operational definition for the use of the MMT:

“Manual muscle tests evaluate the ability of the nervous system to adapt the muscle to meet the changing pressure of the examiner’s test. This requires that the examiner be trained in the anatomy, physiology, and neurology of muscle function. The action of the muscle being tested, as well as the role of synergistic muscles, must be understood. Manual muscle testing is both a science and an art. To achieve accurate results, muscle tests must be performed according to a precise testing protocol.

The following factors must be carefully considered when testing muscles in clinical and research settings:

• Proper positioning so the test muscle is the prime mover
• Adequate stabilization of regional anatomy
• Observation of the manner in which the patient or subject assumes and maintains the test position
• Observation of the manner in which the patient or subject performs the test
• Consistent timing, pressure, and position
• Avoidance of preconceived impressions regarding the test outcome
• Nonpainful contacts – nonpainful execution of the test
• Contraindications due to age, debilitative disease, acute pain, and local pathology or inflammation”

In physical therapy research, the “break test” is the procedure most commonly used for MMT, and it has been extensively studied . This method of MMT is also the main test used in chiropractic, developed originally from the work of Kendall and Kendall .

In physical therapy the “break test” has the following operational definition . The subject is instructed to contract the tested muscle maximally in the vector that “isolates” the muscle. The examiner resists this pressure until the examiner detects no increase in force against his hand. At this point an additional small force is exerted at a tangent to the arc created by the body part being tested. The initial increase of force up to a maximum voluntary strength does not exceed 1 sec., and the increase of pressure applied by the examiner does not exceed a 1-second duration. “Strong” muscles are defined as those that are able to adapt to the additional force and maintain their contraction with no weakening effect. “Weak” muscles are defined as those unable to adapt to the slight increase in pressure, i.e., the muscle suddenly becomes unable to resist the test pressure.””

Kendall et al (1993) state:
“As tools, our hands are the most sensitive, fine tuned instruments available. One hand of the examiner positions and stabilizes the part adjacent to the tested part. The other hand determines the pain-free range of motion and guides the tested part into precise test position, giving the appropriate amount of pressure to determine the strength. All the while this instrument we call the hand is hooked up to the most marvelous computer ever created. It is the examiner’s very own personal computer and it can store valuable and useful information of the basis of which judgments about evaluation and treatment can be made. Such information contains objective data that is obtained without sacrificing the art and science of manual muscle testing to the demand for objectivity.”

According to Walther (1988):
“Presently the best ‘instrument’ to perform manual muscle testing is a well-trained examiner, using his perception of time and force with knowledge of anatomy and physiology of muscle testing.”

Cuthbert and Goodheart conclude by saying, “Regardless of the methods or equipment one uses to standardize MMT in a clinical or research setting, it is most important that the test protocol be highly reproducible by the original examiner and by others.”

Results

More than 100 studies related to MMT and the applied kinesiology chiropractic technique (AK) that employs MMT in its methodology were reviewed, including studies on the clinical efficacy of MMT in the diagnosis of patients with symptomatology. With regard to analysis there is evidence for good reliability and validity in the use of MMT for patients with neuromusculoskeletal dysfunction. The observational cohort studies demonstrated good external and internal validity, and the 12 randomized controlled trials (RCTs) that were reviewed show that MMT findings were not dependent upon examiner bias.

Conclusion

The MMT employed by chiropractors, physical therapists (including Osteopaths), and neurologists was shown to be a clinically useful tool, but its ultimate scientific validation and application requires testing that employs sophisticated research models in the areas of neurophysiology, biomechanics, RCTs, and statistical analysis.

The above study can be found in greater detail by visiting the following website;
http://www.etouchforhealth.com/research/muscle_testing.html