What is Resisted isometric movements?

Working with the patients in the clinic and assessing their structural affection has always been a mind scratching job. Multiple tests are performed but there remains a doubt that which structure/ tissue is involved – contractile or non- contractile/ inert tissue. Contractile tissue refers to Muscle, Tendon, Musculo – Tendinous junction, Teno – Periosteal junction, Nerves, etc.  

Contractile tissue assessment involves voluntary contraction of muscles. These contractions include strong isometric contraction, multiple angle isometrics or concentric/ eccentric contraction. During this testing, it is checked if there is any pain or not and if it is then what is the intensity and quality of pain. Along with the pain it is also assessed what is the strength of contraction and which type of contraction is painful as well as weak.

For solving the above queries, the testing is done by Resisted Isometric Movements. However these movements are always tested last in the examination of the joints. This type of movement consists of a strong, isometric voluntary contraction of muscles and primarily detects muscles as well as nerves supplying the tested muscles.

• If the muscle, its tendon or the bone into which they insert is at fault, pain & weakness result; the severity of pain and weakness helps to judge the degree of injury and patient’s pain threshold.

Some of the important points to be taken care of while assessing:

1. There should not be any movement while performing the test because if movement occurs then inert tissue will also move and it will be difficult to find out which is the offending structure- contractile or inert.
2. The test joint should be put in neutral or resting position in order to minimize tension on inert tissue.
3. The movements should be done in resting position of the joint as in this position muscle is in its optimal length so that maximum force can be elicited.
4. Moreover this position can be modified if required when assessing for tight or lengthened structures as well performing multiple angle isometric testing.
5. This test involves isometric hold so it is essential to have the muscle strength of grade 3 to 5 on the muscle test grading scale.
6. If there is difficulty in differentiating between grades 4 and 5, eccentric break test can be used. The test starts as an isometric contraction, but then assessor applies sufficient force to cause eccentric contraction or break in the isometric contraction.
7. Post testing isometrics, other types of contraction can also be checked for according to patient’s complain.

Steps to perform Resisted Isometric Movements:

1. The joint is placed in neutral or resting position. Every joint has a specific resting position.
2. The patient is asked to perform strong isometric contraction, not to move the part and the assessor will resist with almost equal amount of force to prevent any movement from occurring and also to ensure that patient exerts maximum effort.
3. However movement cannot be completely eliminated, but this will minimize it.

After these movements are performed, the assessor determines the contractile tissue affected by judging the degree of pain & strength of contraction. Along with these movements, functional testing, myotomes assessment, manual muscle testing, palpation and special tests are also equally important.

Active movements as well as passive movements can also be performed. And it has been observed that if contractile tissue is injured, active movement is painful in one direction (contraction) and passive movement is painful in opposite direction (stretch). Resisted isometric movement is painful in the direction of active movement.

There are 4 classic Patterns of contractile tissue lesions, according to pain & strength. They are as follows:

• Strong & Pain free: – There is no lesion of the contractile tissue (muscles as well as nerves supplying) which is being tested regardless of being tender on touch.

• Strong & Painful – In this there is local lesion of muscle or tendon. 1^st or 2^nd degree muscle strain. 2^nd degree strain produces more muscle weakness and pain than 1^st degree strain.

There can be tendinitis, tendinosis, paratenonitis or paratenonitis with tendinosis or partial avulsion fracture, but in this contraction will be strong (not as good side) and painful, pain will be around the tendon and not the muscle.

• Weak & Painful: – This is seen in cases of severe lesion around of joint such as fracture. Weakness is usually caused by reflex inhibition of muscles around the joint secondary to pain.

• Weak & Pain free: – This indicates complete rupture of muscle or tendon (3^rd degree) or involvement of peripheral nerve or nerve root supplying that muscle. With neurological involvement, assessor must differentiate between affection of (a) peripheral nerve by checking muscles & (b) nerve root by checking myotomes and dermatomes. Differentiate between UMN & LMN lesions.

3^rd degree strains usually are painless, but many a times along with this there is 1^st or 2^nd degree strain of surrounding muscles resulting into pain. To find out 3^rd degree strain, one must check for presence of hole or gap in muscle by palpation or check the muscle bulk when contraction is attempted and how it gives appearance of obvious deformity.

Reference

• Magee DJ. “Orthopaedic Physical Assessment.” 5^th Philadelphia: WB Saunders. 2012.
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