Muscle weakness happens when your full effort doesn’t produce a normal muscle contraction or movement.
It’s sometimes called:
- reduced muscle strength
- muscular weakness
- weak muscles
Whether you’re ill or you simply need rest, short-term muscle weakness happens to nearly everyone at some point. A tough workout, for instance, will exhaust your muscles until you’ve given them a chance to recover with rest.
If you develop persistent muscle weakness, or muscle weakness with no apparent cause or normal explanation, it may be a sign of an underlying health condition.
Voluntary muscle contractions are usually generated when your brain sends a signal through your spinal cord and nerves to a muscle.
If your brain, nervous system, muscles, or the connections between them are injured or affected by disease, your muscles may not contract normally. This can produce muscle weakness.
Many health conditions can cause muscle weakness.
- neuromuscular disorders, such as muscular dystrophies, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS)
- autoimmune diseases, such as Graves’ disease, myasthenia gravis, and Guillain-Barré syndrome
- thyroid conditions, such as hypothyroidism and hyperthyroidism
- electrolyte imbalances, such as hypokalemia (potassium deficiency), hypomagnesemia (magnesium deficiency), and hypercalcemia (elevated calcium in your blood)
Other conditions that may cause muscle weakness include:
- herniated disc
- chronic fatigue syndrome (CFS)
- hypotonia, a lack of muscle tone that’s usually present at birth
- peripheral neuropathy, a type of nerve damage
- neuralgia, or sharp burning or pain following the path of one or more nerves.
- polymyositis, or chronic muscle inflammation
- prolonged bed rest or immobilization
- alcoholism, which can cause alcoholic myopathy
Muscle weakness can also be caused by complications from certain viruses and infections, including:
Botulism, a rare and serious illness caused by Clostridium botulinum bacteria, can also lead to muscle weakness.
Prolonged use of certain drugs may also result in muscle weakness.
These drugs include:
- statins and other lipid-lowering agents
- antiarrhythmic drugs, such as amiodarone (Pacerone) or procainamide
- colchicine (Colcrys, Mitigare), which is used to treat gout
If you experience muscle weakness for which there’s no normal explanation, make an appointment with your healthcare provider.
You’ll be asked about your muscle weakness, including how long you’ve had it and which muscles have been affected. Your healthcare provider will also ask about other symptoms and your family medical history.
Your healthcare provider may also check your:
- muscle tone
If needed, they may order one or more tests, such as:
Once they’ve determined the cause of your muscle weakness, your healthcare provider will recommend appropriate treatment. Your treatment plan will depend on the underlying cause of your muscle weakness, as well as the severity of your symptoms.
Here are some of the treatment options for conditions that cause muscle weakness:
Physical therapists can suggest exercises to improve your quality of life if you have conditions such as MS or ALS.
For example, a physical therapist might suggest progressive resistive exercise to help someone with MS strengthen muscles that have become weak from lack of use.
For someone with ALS, a physical therapist might recommend stretching and range of motion exercises to prevent muscle stiffness.
Occupational therapists can suggest exercises to strengthen your upper body. They can also recommend assistive devices and tools to help with day-to-day activities.
Occupational therapy can be especially helpful during the stroke rehabilitation process. Therapists can recommend exercises to address weakness in one side of your body and help with motor skills.
Over-the-counter (OTC) pain relievers, such as ibuprofen or acetaminophen, can help manage pain associated with conditions such as:
- peripheral neuropathy
In some cases, muscle weakness can be a sign of something very serious, such as a stroke.
If you experience any of the following symptoms, call 911 or your local emergency services immediately:
- sudden onset of muscle weakness
- sudden numbness or loss of feeling
- sudden difficulty moving your limbs, walking, standing, or sitting upright
- sudden difficulty smiling or forming facial expressions
- sudden confusion, difficulty speaking, or trouble understanding things
- chest muscle weakness resulting in difficulties breathing
- loss of consciousness