Could you please help me settle an argument? Is Delayed Onset Muscle Soreness (DOMS) caused by microtears in muscle fibers and connective tissue? Or, is it due to the accumulation of lactic acid? I thought that lactic acid was eliminated within about 60 minutes of returning to an aerobic state after the anaerobic production of lactic acid. Can you experience muscle soreness at 48 to 72 hours after exercise, from lactic acid accumulation? Does it make a difference if it is the result of a 5K or a 20-mile training run?
Lactic acid accumulation however, may cause some discomfort-not pain-during and immediately after the intense anaerobic exercise bout and may last up to an hour or so, depending on your cool down. DOMS, on the other hand, produces real pain-tenderness on touch, muscle stiffness, and pain with any use of the muscle. Although there is still controversy, most agree that some type of muscle damage and the resulting inflammation causes DOMS. The theory I support suggests that damage to the actin and myosin filaments in skeletal muscle after performing unaccustomed eccentric contractions causes DOMS.
During rest, lactic acid is removed at the same rate as it is being created. As the intensity of the activity increases so does the amount of lactic acid being created. Accumulation starts to build but is not a problem until the exercise intensity requires the anaerobic system to become the primary energy source.
After the exercise bout, an active cool down allows the skeletal muscle to convert the lactate back into pyruvate, which is used to produce energy. Additional removal occurs in the liver by conversion into glucose and released back into the blood or stored as glycogen. During steady aerobic activity, whether a 5K or a marathon, little lactic acid accumulates, even if performed at maximum.
With an active cool down, removal is very rapid and baseline levels are reached within a few hours. On the other hand, a large volume of high intensity intermittent exercise like interval training will generate high levels of lactate and will require some additional time for removal, but should be back to baseline well before any DOMS would be noticed.