Delayed onset muscle soreness (DOMS), also called muscle fever, is the pain and stiffness felt in muscles several hours to days after unaccustomed or strenuous exercise.
The soreness is felt most strongly 24 to 72 hours after the exercise.[1][2]:63 It is thought to be caused by eccentric (lengthening) exercise, which causes microtrauma to the muscle fibers. After such exercise, the muscle adapts rapidly to prevent muscle damage, and thereby soreness, if the exercise is repeated.[1][2]:76
Delayed onset muscle soreness is one symptom of exercise-induced muscle damage. The other is acute muscle soreness, which appears during and immediately after exercise