During excessive muscular activities such as a marathon, lactate fermentation occurs in muscles to serve as a source of ATP to sustain muscle contraction. The lactate produced during lactate fermentation is removed aerobically from muscles. Lactate threshold or anaerobic threshold refers to the intensity of physical activity that produces the blood lactate at a fast rate than its removal.
Increased intensity of exercise or physical activity increases lactate production. As the intensity reaches the point at which lactate cannot be removed from the body fast enough, it is accumulated and causes fatigue in muscles. Therefore, the lactate threshold is the upper limit that can be sustained aerobically by the body without any accumulation of lactate.
