Muscle pain, or myalgia, is quite common and can be felt anywhere there is muscle tissue on the body. The pain is usually localised and affects a small number of muscles at a time. Systemic muscle pain, which is felt throughout the body, is different and is more often the result of an infection, an illness or a side effect of a medication.
Muscle pain is typically related to tension, overuse, or due to muscle injury resulting from exercise or physically demanding work. The pain tends start 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 the whole body. For example, some infections (including the flu) and disorders that affect connective tissues throughout the body can cause muscle pain.
Common causes of muscle pain include tension or stress, injury (sprains) or using a muscle too much. Another cause may be fibromyalgia, a condition that causes tenderness in the muscles and surrounding soft tissue as well as sleep difficulties, fatigue or headaches.