What is aerobic threshold?
Aerobic threshold is where the level of lactate in the blood first starts to rise. Aerobic fitness level is determined by an individual’s heart rate at the aerobic threshold. For example, the aerobic threshold of people with a poor aerobic fitness may be at 60% of their HR max, whereas for trained athletes it may even be at 85% of their HR max.
A higher aerobic threshold allows you to train at higher intensity without lactate building up. When you’re aiming to develop your aerobic threshold, the key is to emphasise low-intensity training. The increased capillaries and the developed fatty acid metabolism help to improve your body's ability to increase training intensity, without increasing the levels of lactic acid. In practice this means you can keep going at a higher intensity for a longer time.
What is anaerobic threshold?
Your anaerobic threshold is the highest exercise intensity your body can sustain, for a prolonged period, without lactate substantially building up in your blood. When you go over your anaerobic threshold, your anaerobic metabolism increases and blood lactate starts to accumulate, this causes muscles to become stiff.
Just like the aerobic threshold, you can increase your anaerobic threshold. What this means is that you will be mainly training slightly below the threshold and only going over it every now and again. As your anaerobic threshold increases, you will be able to train with a higher intensity without the lactate stiffening your muscles.
How to find out your individual thresholds
There are several ways to find out your anaerobic and aerobic thresholds. One of the most popular ways is an exercise test, where the intensity level increases step-by-step. Blood samples can be taken from your finger to monitor the changes in the lactate concentration of your blood. That is why aerobic and anaerobic thresholds are often referred to as lactate thresholds (lower and upper LT, or LT1 and LT2).
When the level of lactate in your blood goes up, it leads to increased ventilation and CO2 production, so your aerobic and anaerobic threshold can also be determined from ventilation and respiratory gases. In practice this means taking an exercise test while wearing a mask that measures your oxygen intake and measures the amount of CO2 as you exhale. These thresholds can also be referred to as ventilatory thresholds (VT1 and VT2).