Efficiency Factor
We have known for decades that if heart rate during an all-aerobic (below lactate/anaerobic threshold) workout rises while the intensity (power or pace) stays the same then the athlete is not operating efficiently and his or her aerobic endurance is questionable. The same is true if heart rate stays the same and power decreases or the pace slows.
To determine EF the software divides normalized power or normalized graded pace by average heart rate for the workout or selected workout segment such as an interval.
By comparing the resulting ratios for similar workouts over several weeks you can measure improvements in aerobic efficiency. To be reliable the workouts need to be quite similar by making sure all of the elements are alike. This includes level of pre-workout fatigue, equipment, course, weather conditions, altitude, pre-workout nutrition (especially stimulants such as caffeine), warm-up and perhaps even time of day. The more similar all of these are from one session to the next the more valuable the information is. If you are making good aerobic progress progress then your EF will rise over the course of a few weeks. Watch the video below to see this in action in training peaks.
Coach Cliff
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