Efficiency Index (EI)
Efficiency Index (EI) measures of how much speed you achieved in relation to your power output.
EI is useful for comparing workouts on identical courses in similar conditions, to determine if you are improving by getting more speed per watt (data from a power meter is required for EI). Higher EI numbers indicate greater efficiency, such as getting faster at the same power, or achieving the same speed or pace using less power.
If you use a running power meter, EI is especially informative when you test it at your current Running FTP. On an identical course with similar conditions, run and try to maintain your current Running FTP. Afterward, when analyzing in SportTracks, determine if your EI improved or not, and compare this run with other identical workouts. This is called EI @ FT. If your EI isn’t improving at your FTP, train to improve your running form and test again.
Find it in SportTracks
EI is found by clicking twice on the Total Block for Pace at the top of a workout detail page:
EI can also be listed as a metric on the SportTracks Workouts page, where you can easily stack workouts and filter them to list chronologically: