Fatigue: towards an analysis and a unified definition.

Fatigue is the commonest, yet least understood and most neglected symptom in medicine. A physiological formula for fatigue is proposed, based on the concept of a reduction of the "latent capacity" of cells, tissues and organs whose states are constantly monitored by the brain. Reduced "latent capacity" is postulated as being the sought-after, non-specific alarm signal of the General Adaptation Syndrome of Selye (G.A.S.). The relationship between fatigue and pain is discussed. Reduced "latent capacity" is postulated as being the common thread in the different kinds of fatigue - physiological, pathological, psychogenic, acute and chronic.