Glossary: Variability Index (VI)
Variability Index is a simple measure for how steady or unsteady your power output during a ride (or run) was. For almost steady activities, VI should be below 1.05. Interval workouts or similar may have a VI of 1.2 or more.
VI [-] = xPower [W] / avg. Power [W]
The Variability Index can also be determined in terms of pace. xPace and xGAP are determined in the same way as xPower.
VI [-] = xPace [m/s] / avg. Pace [m/s]
VI [-] = xGAP [m/s] / avg. GAP [m/s]