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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.
What Is a Muscle Strain? Muscle strain is injury to muscle as a result of strenuous activity. Almost anyone can put undue tension on muscles during the course of normal daily activities, with sudden, quick heavy lifting, during sports, or while performing work tasks. Muscle strain is sometimes referred to as muscle pull.