Delaye onset muscle soreness (DOMS) is the pain or discomfort often felt 24 to 72 hours after exercising and subsides generally within 2 to 3 days. Once thought to be caused by lactic acid buildup, a more recent theory is that it is caused by tiny tears in the muscle fibers caused by eccentric contraction, or unaccustomed training levels. Since lactic acid disperses fairly rapidly, it could not explain pain experienced days after exercise, and some concentric-only exercises produce lactic acid, but rarely produce DOMS.