Fatigue

Fatigue is a state of being without energy for a prolonged period of time. The word fatigue is used in two contexts: in the medical sense, and in the sense of normal tiredness. In the medical sense, fatigue is seen as a symptom, and is sometimes associated with medical conditions including autoimmune disease, organ failure, mood disorders, heart disease, infectious diseases, and post-infectious-disease states. However, fatigue is complex and in up to a third of primary care cases no medical or psychiatric diagnosis is found. In the sense of tiredness, fatigue often follows prolonged physical or mental activity. Physical fatigue results from muscle fatigue brought about by intense physical activity. Mental fatigue results from prolonged periods of cognitive activity which impairs cognitive ability, can manifest as sleepiness, lethargy, or directed attention fatigue, and can also impair physical performance.