Home > Medical > Symptoms Updated 11 February 2013 Muscle weakness Uncharacteristic muscle weakness or inability of the muscles to perform normally, relative to that person’s normal ability. 0 Definition Uncharacteristic muscle weakness or inability of the muscles to perform normally, relative to that person’s normal ability. The symptom will usually be identified when a person is performing exercise or some muscular activity, such as climbing stairs, or carrying goods. It is however distinct from the weakness (or tiredness) that many will feel when run-down and fatigued as a result of normal activities. Because muscle contraction requires a signal from the brain, down the spinal cord, to the muscle, the cause of true weakness may lie anywhere along this chain. It may thus be metabolic, neurological, toxic or directly muscular. NEXT ON HEALTH24X ACNE 2019-11-18 06:57 More: MedicalSymptoms advertisement Read Health24’s Comments Policy Comment on this story 0 comments Comments have been closed for this article. Logout Comment 0 characters remaining Share on Facebook Loading comments... Other news Medical Coronavirus 101 – here's what you need to know Medical Coronavirus in SA: All the confirmed cases Medical Coronavirus: What are the criteria for a suspected case? Medical Coronavirus: Basic protective measures Medical Here's how quality sleep can help you fight the new coronavirus Covid-19: SA Government's Online Coronavirus Portal Live healthier Lifestyle » E-cigarettes: Here are five things to know E-cigarettes have become hugely popular in the past decade, but a rash of vaping-linked deaths and illnesses in the US is feeding caution about a product that's already banned in some places. Allergy » Ditch the itch: Researchers find new drug to fight hives A new drug works by targeting an immune system antibody called immunoglobulin E, which is responsible for the allergic reaction that causes hives.