Muscle pain is most often related to tension, overuse, or muscle injury from exercise or physically demanding work. The pain tends to involve specific muscles and starts during or just after the activity. It is often obvious which activity is causing the pain. Muscle pain also can be a sign of conditions affecting your whole body. For example, some infections (including the flu) and disorders that affect connective tissues throughout the body (such as lupus) can cause muscle pain. One common cause of muscle aches and pain is fibromyalgia, a condition that causes tenderness in your muscles and surrounding soft tissue, sleep difficulties, fatigue, and headaches.
