Muscle Weakness

What is muscle weakness?

Muscle weakness is when muscles aren’t as strong as they should be. It can happen for many reasons, many of which are temporary and normal. But muscle weakness can also be a sign or symptom of an underlying medical issue.

Muscle weakness can feel different, depending on what’s causing it. You might experience:

• Loss of strength
• Difficulty doing familiar tasks or activities
• Pain when using the affected muscles
• Difficulty with balance or stability when standing or walking
• Trembling or shaking

Are there different stages or severity levels?

Experts use a strength scale that the Medical Research Council of the United Kingdom created in the early 1940s. That scale uses the following 0 to 5 grading system to evaluate muscle strength in your arms and legs:

• No muscle movement or strength
• Flickers or traces of muscle movement, like twitching
• Muscle movement without working against gravity
• Muscle movement working against gravity
• Muscle movement with some force resisting the movement
• Muscle movement against full force resisting the movement

What are the most common causes of muscle weakness?

There are a few key causes of muscle weakness:

• Structural effects
• Cellular effects
• Nervous system conditions and injuries
• Chronic diseases

Structural effects

This usually involves damage to the muscle itself or some of the related connective tissue. Examples include:

• Muscle strains
• Sprained or torn ligaments
• Broken bones

Cellular effects

Muscle weakness can happen when your muscle cells themselves aren’t working properly. Cell-related reasons that you can have muscle weakness include:

• Malnutrition, vitamin or mineral deficiencies or electrolyte imbalances
• Muscle disorders like muscular dystrophies
• Muscle atrophy or muscle mass loss (sarcopenia)

Nervous system conditions and injuries

Your muscles rely on nerve signals to tell them when to flex and relax. Without those signals, your muscles may not work together or at all. Nervous system conditions that can cause muscle weakness include:

• Certain types of migraines, especially hemiplegic migraines
• Infections like botulism
• Pinched nerves
• Seizures
• Spinal conditions like herniated disks or cauda equina syndrome
• Spinal cord injuries
• Strokes and transient ischemic attacks (TIAs)
• Toxic effects from chemicals like organophosphates (often found in pesticides)

Chronic diseases

These are long-lasting conditions that can cause muscle weakness. Many of these are autoimmune conditions or inflammatory diseases. Examples include:

• Guillain-Barré syndrome
• Diseases like amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease)
• Multiple sclerosis (MS)
• Recovering from severe illnesses like sepsis or a heart attack

How is muscle weakness treated?

The treatment for muscle weakness depends mainly on its cause and your health history. Some examples of treatments include:

• Physical therapy to improve strength
• Nutritional support to provide vital nutrients
• Immobilization and/or rest to let damaged tissues heal
• Surgery or other procedures to repair damage
• Medications to treat other symptoms like pain or underlying conditions like epilepsy

In some cases, there’s no treatment for what’s causing your muscle weakness. Examples of that would be long-term neurological damage from a stroke or spinal cord injury. In those cases, supportive care may help you adapt to or work around any changes. Your healthcare provider can tell you more about the treatment options for your case. They can also tailor the information they provide to the details of your circumstances.

Is muscle weakness preventable?

Some causes of muscle weakness are preventable, but many aren’t. Some things you can do to reduce your risk of having muscle weakness include:

• Train up. Strength training can increase your physical strength. That may help reverse or prevent later muscle weakness.
• Know your limits. Don’t overwork your muscles to the point of injury.
• Protect your nervous system. Wear protective gear like helmets or padding during recreational or work activities. Doing so can prevent brain, spine and nerve injuries. And wearing seat belts can prevent injuries from moving vehicle crashes.
• Manage chronic conditions. This can keep some conditions from flaring up and causing muscle weakness. An example of this would be taking epilepsy medication to prevent seizures.

When should this symptom be treated by a doctor or healthcare provider?

Muscle weakness needs medical attention if it lasts more than a few days or starts to interfere with your regular routine.

You need emergency medical attention when you have muscle weakness that:

• Starts suddenly
• Affects only one side of your body
• Affects just one limb (like an arm or leg)
• Spreads from one part of your body to others