Fatigue

Fatigue is a term that has evolved significantly over its history from routine labor to extreme tiredness. In the military, fatigue is low-skill non-combat physical work like cleaning, kitchen chores, or fence painting. Fatigue or fatigues may also be used to indicate clothes of the military personnel performing those routine duties. In psychology, fatigue is a subjective sudden or gradual feeling of tiredness. In human factors, fatigue is a factor that can cause a human error. In mechanical engineering, fatigue is one of causes of material's failure or device's loss of ability to function.

Types

Physical fatigue

Physical fatigue is inability to work or work properly. For materials, fatigue is the tendency to break under constant or repeated stress. For devices, fatigue is the loss of ability to perform properly usually after extended periods of functioning. For human beings, physical fatigue is weariness or exhaustion from exertion, which is caused by deficit of sleep, stress, fatty foods, circadian rhythms, unclean air, and hard labor.

Mental fatigue

Mental fatigue is a feeling of extreme tiredness usually after extended or repeated performance especially if one is doing non-physical tasks. Usually, mental fatigue includes a feeling of monotony and boredom. Mental fatigue can also indicate a state or attitude of indifference or apathy brought on by overexposure, for instance, to a repeated series of similar events or appeals.

Mental fatigue can be also caused by the same factors like physical fatigue, so simply stretching or other physical exercises, or stepping into the fresh air once in a while can break the monotony.