Muscle pain

Muscle pain (myalgia): Causes and mechanisms of onset

Muscle pain, or myalgia, is an extremely common symptom that can range from mild discomfort to severe, exhausting pain that limits movement. It may affect a single muscle group or be spread throughout the body. The causes of myalgia are diverse: from ordinary physical overexertion to serious systemic diseases.

Most common causes of muscle pain

• Overexertion or injury: This is the most obvious cause. Excessive physical load, especially unusual, causes microscopic damage to muscle fibers. The healing process is accompanied by inflammation and pain, known as "delayed onset muscle soreness" or delayed muscle pain. Direct trauma (impact, strain) also causes pain and inflammation.
• Viral infections: "Body aches" are a classic symptom of flu and many other upper respiratory infections. The pain is caused both by the direct action of the virus on muscle tissue and by the overall inflammatory response of the body (cytokine production).
• Stress: Chronic psycho‑emotional tension forces muscles, especially in the neck and shoulder area, to stay in constant tone. This disrupts their blood supply and leads to pain.
• Deficiency states: Lack of electrolytes such as potassium or magnesium can cause muscle cramps and pain. Dehydration is also an important factor.

When is muscle pain a cause for concern?

You should see a doctor if the pain:

• Is very severe and appears without an obvious cause.
• Lasts more than a few days.
• Is accompanied by pronounced swelling, redness, or weakness of the affected limb.
• Is accompanied by fever and rash.

This may be a sign of more serious conditions, such as systemic connective‑tissue diseases (e.g., fibromyalgia) or myositis (autoimmune inflammation of the muscles). More information about joint pain can be read on the page "Joint pain".