Delayed onset muscle soreness (DOMS), sometimes referred to as "cramps", 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.
DOMS typically causes stiffness, swelling, strength loss, and pain. Continued exertion of sore muscles can cause further swelling and pain, and lengthen the period of muscular soreness.
Stretching before and after exercise has been suggested as a way of reducing DOMS, as has warming up before exercise, cooling down afterwards, and gently warming the area. However, there is also evidence that the effect of stretching on muscle soreness is negligible. Overstretching itself can cause DOMS. Some recommend contrast showers as a treatment, alternating between cold and hot water; it may increase circulation.
(Wikipedia)
