VO2max and anaerobic threshold are two primary indicators of performance level in endurance events. Whether it’s running, cycling, or swimming, long events require a participant to use fuel sources in an efficient manner in order to perform at a high level.

VO2 stands for “volume of oxygen” and is a measurement of the rate at which one can take in oxygen and distribute that oxygen to the muscles. VO2max is the maximum rate at which oxygen is consumed and distributed to muscles. Oxygen is needed to burn carbohydrates and fat for energy. This is important for endurance athletes in that the faster oxygen is made available for converting carbs and fats to energy, the more work can be done. A high VO2max measurement is an indicator of an increased ability to perform endurance exercise.

Anaerobic threshold is the point at which blood lactate levels rise above resting levels. What does this mean? At the particular point (exercise intensity) that blood lactate levels increase, the main fuel source for energy is carbohydrate as opposed to fat. This is important because the ideal fuel source for endurance athletes is fat. Fat is essentially an infinite fuel source in the body. Carbohydrate stores, on the other hand, can be depleted causing a decrease in performance levels. The idea for endurance athletes is to obtain a high anaerobic threshold so that the oxygen being consumed will oxidize fat for energy. A high anaerobic threshold simply means that a person can exercise at a high intensity and still use fat stores rather than carbohydrates as a fuel source. This allows the athlete to exercise harder, longer.

It is possible for a person to have a relatively low VO2max and still be a great endurance athlete. The anaerobic threshold is measured as a percentage of VO2max. One could have a moderate VO2max but a high anaerobic threshold of 80-90%. This would mean that this person could exercise at an intensity of 80-90% of his or her maximum effort before using carbohydrates as the main fuel source. So, while it is important to provide muscles with adequate amounts of oxygen (VO2) to convert fuel to energy, it is equally important to have the ability to use fat as fuel at high intensities for endurance athletes.

Improvements in both VO2max and anaerobic threshold can be made through training. Aerobic exercise alone can improve one’s VO2max. To increase the anaerobic threshold, interval training is recommended. Performing shorter, but higher intensity training sessions periodically will improve one’s anaerobic threshold.