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Muscle Weakness
Muscle weakness happens when your full effort doesn't produce a normal muscle movement. Learn when it might be a sign of a serious medical cond...

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What Is Muscle Weakness?

Feeling weak is not all that uncommon. Whether you are ill or simply need rest, muscle weakness happens to nearly everyone at some point in their life. 

The definition of true muscle weakness, however, is when your full effort does not produce a normal muscle contraction or movement. You may hear it also referred to as reduced muscle strength, muscular weakness, or weak muscles. 

A voluntary muscle contraction is usually generated when the brain sends a signal through the spinal cord and nerves to a muscle. If the brain, the nervous system, the muscles, or the connections between are injured or affected by disease, the muscle won’t contract normally and muscle weakness is the resultant symptom.

This is different from the weakness you may feel as a result of a tough workout, for instance. The difference is that a workout will exhaust muscles and there is recovery with rest, but true muscular weakness is a sign of something deeper.

Potential Causes of Muscle Weakness

There are many possible underlying causes for muscle weakness. Possible causes include:

  • chronic fatigue syndrome
  • muscular dystrophy
  • Graves disease
  • Guillain-Barré syndrome
  • hypothyroidism
  • hypotonia (lack of muscle tone, usually present at birth)
  • Lou Gehrig’s disease
  • myasthenia gravis (an autoimmune and muscular disorder)
  • neuralgias (sharp burning or pain in one or more nerve)
  • peripheral neuropathy (nerve damage)
  • polio
  • rheumatic fever
  • West Nile virus
  • hypercalcemia (elevated calcium in the blood)
  • botulism (a rare and serious illness caused by the bacterium Clostridium botulinum)
  • polymyositis (chronic muscle inflammation)
  • stroke
  • prolonged bed rest or immobilization

Diagnosing the Underlying Cause of Muscle Weakness

When you experience muscle weakness and there is no normal, logical explanation for it, make an appointment to see your doctor. Your doctor will ask you questions about the weakness, how long you have had it, and what muscles are affected. The evaluation will also determine if muscle atrophy is present.

Your doctor will also check your reflexes, sensation, and muscle tone. If further investigation is needed, the doctor may order tests including:

  • CT scan
  • MRI
  • nerve tests
  • electromyography (tests nerve activity in the muscles)
  • blood tests

Treatment Options for Muscle Weakness

Once the cause of your muscle weakness is determined, your doctor can decide on proper treatment. The treatment will depend on the underlying problem and the severity of the symptoms. In some cases, physical therapy may be helpful. In others, medication may be the best option for relief.

Recognizing a Potential Emergency Situation

In some cases, muscle weakness can be a sign of something very serious like a stroke. If you experience any of the following symptoms, call 911 immediately.

  • Any sudden onset of muscle weakness, such as being unable to move an arm or leg, or problems walking, standing, or sitting upright.
  • Any sudden onset of being unable to smile or make facial grimaces.
  • Any chest muscle weakness resulting in difficulties breathing.
Written by: JC Jones MA, RN
Edited by:
Medically Reviewed by:
Published: Dec 17, 2014
Published By: Healthline Networks, Inc.
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