Physical or mental fatigue is a condition characterized by a feeling of tiredness and exhaustion that can affect both the body and mind. Physical fatigue occurs when the body is forced to undergo strenuous physical exertion, such as intense training, heavy manual labor, or prolonged illness. Mental fatigue, on the other hand, is the result of strenuous mental exertion, such as studying for long periods of time, intense computer work, or lingering worries.