Lactic Acid

LACTIC ACID

Lactic acid is a by-product of anaerobic energy metabolism in muscles. When the intensity of exercise is high and the body cannot supply enough oxygen for aerobic metabolism, the muscles switch to anaerobic pathways, producing lactic acid (more precisely, lactate).

The accumulation of lactate (and the associated hydrogen ions) in the muscles causes the burning sensation and fatigue experienced during intense efforts. The "lactate threshold" is the intensity level at which lactate begins to accumulate faster than the body can clear it. Training at and around the lactate threshold is a key method for improving cycling endurance.

Contrary to popular belief, lactic acid is not the primary cause of muscle soreness experienced in the days after exercise (DOMS). It is cleared from the muscles within an hour or so after exercise.