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Massage Today
September, 2008, Vol. 08, Issue 09

Weakness

By Ben Benjamin, PhD

Question: What is the difference between specific muscle weakness and generalized weakness?

Answer: Specific muscle weakness is caused by damage to a particular nerve (e.g., by compression of a nerve by a bulging intervertebral disc).

While the muscles innervated by that nerve become weak, other muscles are unaffected. Generalized weakness is caused by disuse, with the result that all the muscles in a particular area of the body become weak.

An example of specific muscle weakness would be gross weakness of the triceps and flexor carpi radialis muscles, which are both innervated by the C7 nerve. A disc compression of the C7 nerve would cause those two muscles to be weak during testing, while the other muscles of the shoulder and forearm remain at their normal strength. In some cases of specific weakness, there is no disc involvement. Instead, other factors are causing a nerve to become inflamed for several weeks or months. For example, neuritis of the suprascapular nerve can cause profound weakness in external rotation of the shoulder. 

Generalized weakness commonly occurs when a person has an injury that makes it painful to use a certain part of the body. For example, if a person's right shoulder is very painful and most everything they do with it causes pain, they will begin to restrict their movement and use of that shoulder to avoid suffering more pain. After a few weeks or months of restricted movement, all of the muscles in the right shoulder area will weaken. The expression "use it or lose it" holds true for muscles as well as for ligaments, tendons and even different parts of our brain.

Understanding the distinction between specific weakness and generalized weakness will help you to differentiate conditions that affect nerve function from other types of injuries or disorders. Muscle weakness can be a distressing symptom. The more you know, the better able you will be to help your clients understand and find treatment for their underlying condition.


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