VO2max is a scientific metric for the maximal oxygen uptake that is highly correlated with one's maximal running performance. Still, two athletes with equal VO2max values do not need to perform equally as their efficiency may differ. Instead of the exact VO2max (which can be measured in a lab), the combination of VO2max and running efficiency is of intereset. The resulting Effective VO2max can be used as direct predictor for upcoming running events.
Runalyze estimates the Effective VO2max for every run with heart rate data based on the relation of heart rate and pace. Optionally, elevation can be taken into account as well. The average of these values will be used as the athlete's current shape. As everybody’s heart rate may behave differently, Runalyze uses an additional individual correction factor which is calculated based on one's best race and its heart rate automatically. Alternatively, athletes can pick a manual correction factor.