The lactate response chart shows the relationship between the exercise load (cycling power output, running speed or swimming pace) and the accumulation of lactic acid in the blood. The aerobic (Lactate threshold 1 = LT1) and anaerobic threshold (Lactate threshold 2 = LT2) can be calculated based on this relationship.
Lactate threshold 1 (LT1)
The aerobic threshold is the first intensity at which there is a sustained increase in blood lactate concentration above resting levels as a responce to progressive exercise. AT can be expressed as heart rate, power/speed.
Lactate threshold 2 (LT2)
The anaerobic threshold is the training intensity at which there is a rapid rise in blood lactate, indicating the upper limit of equilibrium between lactate production and clearance. ANT can be expressed as heart rate, power/speed.
Accumulation of lactate limits performance to periods from 30 sec to 15 min. Exhaustion results through the disturbance of the internal biochemical environment of the working muscles and whole body caused by a high acidosis.
The performance (cycling power output, running speed or swimming pace) of an endurance athlete at his/her aerobic threshold is the most important parameter if he or she has to perform in races of more than two hours.
The aerobic threshold is the point in time at which the use of mixed fuels (fat & carbohydrate) starts to operate. It is a very important guide for fuel economy and should be trained regarding the goal of speed or power at the highest possible level without using much of carbohydrate stores.
The anaerobic systems allow muscles to generate force in the abcense of oxygen (anaerobic); thus these energy systems are the major energy contributors during the early minutes of high-intensity exercise. The anaerobic system is not able to generate the energy when an all-out activity is lasting longer than 120 seconds or for long duration activities. Then the aerobic or oxidative energy system is needed.