Muscle Power Grading / Muscle Strength testing


Muscle power grading or muscle strength testing is an important part of the neurological examination that could reveal details regarding neurologic deficits. The neurological assessment contains motor and sensory examinations. Muscle power grading comes under the motor system examination.

Muscle power grading or muscle strength testing could be performed by physicians, nurses, physical therapists, occupational therapists, chiropractors, and other practitioners. Physical therapists more commonly practice muscle power grading.

Purpose of Muscle Power Grading/Muscle strength Testing 

The main purpose of muscle power grading is to assess the complaint of weakness if there is a suspected neurologic disease or muscle weakness. It Includes

  • Patients who are suffering from brain injury, stroke, spinal cord injury, neuropathy, and other neurological problems.
  • Gait and Balance Issues in Elderly patients.
  • After Joint replacements eg TKR
  • Rehabilitation after any sports injuries eg ACL repair.

The most commonly accepted way of assessing muscle power/strength is the Medical Research Council’s scale (MRC scale) of muscle power. This method involves the testing of key muscles in the upper and lower extremities.

And then grading the power of specific muscle groups for example like in case of large joint muscles (hip or knee joint) or individual muscles for example like muscles of hands or feet in relation to the movement of a single joint on a 0 to 5 scale accordingly.

For example – Muscles producing a common action or actions may be analyzed as a group or every muscle may be analyzed separately. for example, flexor carpi ulnaris and flexor carpi radialis muscles may be analyzed together as a set/group in wrist flexion. While Flexor carpi ulnaris may be analyzed more especially for the action of wrist flexion with ulnar deviation.

Important Things to remember before performing the test

  • Before muscle strength testing is performed, it is important to analyze the limbs or trunk for the tone and bulk of the muscles.
  • Muscle tone is assessed by moving the joints. A lack of tone indicates lower motor neuron lesion and hypertonia indicates upper motor neuron lesions.
  • The limbs are also inspected for their deformity or claws. And if there is any hypertrophy or wasting or any involuntary motions, jerks, etc must be mentioned.
  • Remove tight or restrictive clothing before performing the test. So that the examiner should be able to visualize the group of muscles or specific muscle that is being tested. And also able to observe the muscle twitch.
  • The examiner should properly stabilize the joint which is being tested. And also take a look at the other muscles so that they do not assist.

MRC Scale for Muscle Strength-

The MRC grading scale records or grades patient’s effort on the scale of 0 to 5:-

MRC grading scale on the basis of muscle response
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Here are the grades of Muscle Strength/Power as analyzed clinically:-

MRC scale as analyzed clinically
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Normally tested muscles are shoulder abductors, elbow flexors, elbow extensors, wrist extensors, finger flexors, hand intrinsics, hip flexors, knee extensors, dorsiflexors, and plantar flexors. However, these muscle groups are generally tested so that important spinal nerves can be assessed systematically.

However, you can more specifically test the thumb abductors like abductor pollicis brevis to assess the median nerve. And the flexor carpi ulnaris to assess the ulnar nerve.

Clinical Significance of Muscle Power Grading-

  • Muscle power grading doesn’t account for musculoskeletal conditions like osteoarthritis, rheumatoid arthritis, or tendinopathy. These conditions may make testing painful or intolerable.
  • However, this test only depends on the patient’s effort which may be bad in certain patients. Finally, the muscle power grading defines strength level but doesn’t directly measure strength.
  • An Alternatives to the Medical Research Council scale (MRC) is the Manual Muscle Testing method which intends to quantify strength directly in terms of pounds, Newtons, or alternative components.
  • Muscle power grading also involves testing functional movements rather than quantifiable strength. Examples of functional tests comprise squatting or rising out from a chair.
  • Functional strength tests give information regarding whether the patient is sufficiently powerful to carry out essential daily life tasks/activities.
  • But, functional strength tests won’t give a grade or numerical quantity which can be monitored over time to judge the improvement.

You May Also Read 

Anterior Drawer Test of the Knee : For detecting Anterior Cruciate Ligament Tear

Chair Sit And Reach Test

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