Weakness

What is weakness?

Weakness is less strength in one or more muscles of the body. Some people experience only the feeling of being weak, but physically experience no loss of strength, for example, feeling weak due to pain. While in some cases loss of strength is only noted during a physical examination. This kind of weakness is also known as “objective weakness”.

What are its main signs and symptoms?

The associated signs and symptoms of weakness are:

• Numbness
• Severe headaches
• Confusion
• Trouble walking
• Tiredness
• Aching or sore muscles
• Sleepiness
• Dizziness
• Loss of appetite
• Shortness of breath

What are the main causes?

The underlying causes of weakness are due to specific health problems such as:

• Low sodium and potassium levels
• Respiratory or urinary tract infections
• Low or high levels of thyroid hormone
• Guillain-Barré syndrome
• Myasthenia gravis (a chronic disorder that weakens the muscles)
• Stroke
• Inactivity as a result of illness, especially in older people
• Intensive care unit (ICU) myopathy (muscle wasting due to an extended stay in the ICU)
• Common myopathies (diseases of the muscle tissue) like muscular dystrophy, hypokalaemia (low potassium levels), and alcoholic myopathy
• Polio
• Physical exertion
• Lack of sleep
• Irregular exercise
• Illnesses like fever
• Poor diet

How is it diagnosed and treated?

The following methods are used for the diagnosis of weakness:

• Physical examination: Motor function, reflexes and cranial nerve functions are examined
• Strength testing: Parameters like weakness against resistance, visible contraction of the muscles, limb movement against gravity, reflexes and sensation are examined.
• Gait is observed
• Medical history is checked for any causes of weakness

Weakness is treated by providing treatment for the underlying cause of weakness. Hospitalisation is advised if required for people with severe weakness. Occupational therapy and physical therapy are also recommended for patients to help minimise loss of muscle function.

1. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; Stroke Signs and Symptoms.
2. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Weakness.
3. Better health channel. Department of Health and Human Services [internet]. State government of Victoria; Fatigue.
4. Merck Manual Professional Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2018. Weakness.
5. Holbrook JH. Weakness and Fatigue. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 213.

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