VO2 max is a key indicator of fitness. VO2 max is defined as the maximum amount of oxygen an individual consumes over one minute during intense physical effort. The more oxygen consumed, the harder muscles can work, and therefore the higher the VO2 max level. A higher VO2 max level indicates a more fit individual.

Medically, VO2 max can be measured by spiroergometry, where the person exercising wears a mask designed to capture maximum oxygen absorption capacity (VO2 max). The mask is worn in front of the mouth and face when running or biking on an ergometer or treadmill.

The higher the VO2 max level is, the more oxygen can be converted in the working muscles to provide energy, the higher is the corresponding endurance capacity.

Steel HR Sport provides a VO2 max estimate based on data including heart rate, age, gender, weight, and pace from a connected GPS running session.