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Freebase(4.82 / 22 votes)Rate this definition: Muscle pain. Myalgia, or muscle pain, is a symptom of many diseases and disorders. The most common causes are the overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections.
Muscle Spasm (Definition) Muscle spasms are typically painful involuntary muscle contracures which can occur in any part of the body, such as the neck, back and legs. There are various causes of muscle spasms such as recent injury or trauma and dehydration.