Muscle fatigue is a symptom that decreases the ability of muscles to perform over time, and it can be associated with a state of exhaustion, often following strenuous activity or exercise. There are many possible causes of muscle fatigue, including improper exercise, long time combat, military training, and some related diseases such as cancer and stroke. Exercise and other physical activity are common causes of muscle fatigue, but this symptom can also be the result of other health conditions, such as Addison’s disease, age, anemia, anxiety, botulism, cerebral palsy, chemotherapy, chronic fatigue syndrome, dehydration, depression, fibromyalgia, hepatitis C, HIV, hypothyroidism, influenza, lack of exercise, lactic acid production, medications, mineral deficiency, muscular dystrophy, myasthenia gravis, myositis, poor muscle tone due to a medical condition, pregnancy, sleep deprivation, stroke, and tuberculosis.

One of the major causes of skeletal muscle fatigue is intracellular acidosis due mainly to lactic acid accumulation. However, there can be multiple causes of muscle fatigue, including not enough oxygen, not enough energy, and phosphate buildup. Muscle fatigue can occur anywhere on the body, and an initial sign of this condition is muscle weakness. Other symptoms associated with muscle fatigue include soreness, localized pain, shortness of breath, muscle twitching, trembling, a weak grip, and muscle cramps.

Treatment for muscle fatigue depends on the underlying cause. For exercise-induced muscle fatigue, rest and recovery alone are generally enough to relieve the symptoms. However, some neurological, muscular, and cardiovascular disorders, as well as inflammatory and autoimmune diseases, can cause severe and persistent muscle fatigue and require immediate medical intervention.