What is the lactate threshold?
Lactate is continuously produced even at rest. It is produced from the breakdown of carbohydrates and the purpose of this metabolic process is to provide us with energy. The concentration of lactate in the blood at rest is ~1-2mmol/L. When we exercise, the concentration of lactate in the blood rises as there is a greater need for energy and thus a greater breakdown of carbohydrate. With light to moderate intensity exercise lactate levels rise slowly because lactate clearance can keep pace with lactate production. However, with high intensity exercise blood lactate levels begin to rise more sharply due to increased production of lactate and / or reduced clearance. Lactate levels can increase by up to 20 times that of resting levels depending on the intensity of the exercise and the
Figure 1: Lactate Threshold (LT) is the running speed at which blood lactate levels begin to rise sharply.
conditioning of the individual. The exercise intensity at which lactate levels begin to rise sharply is known as the lactate threshold (LT), as indicated in figure 1. If exercise continues and lactate levels continue to rise sharply beyond the lactate threshold, the muscles reach a state of acidosis and cannot function as before. The workrate / pace / wattage that the individual is exercising at cannot be maintained and fatigue sets in.