Aerobic Efficiency (AE)
Aerobic efficiency (AE) is the ratio between what you produce (speed or power) and how hard your heart beats for it, measured in a comparable easy endurance effort. Put simply: how much pace do you get per heartbeat?
What is aerobic efficiency?
As your aerobic base grows, you can handle a higher pace or power at the same heart rate — your engine runs more economically. AE captures that in one ratio. A rising AE over the weeks can mean your endurance base is improving: more output at the same effort from your heart.
The pitfall is that many things cloud that ratio. Terrain, wind, heat, fatigue, hydration and simple sensor noise push your heart rate or pace up or down without you being any fitter or less fit. So AE is a trend to read over a longer time, not a number to judge yourself strictly by on each ride.
How do you use AE?
Compare like with like: AE only says something if your easy endurance sessions are comparable in intensity and conditions. An interval session or a ride in full heat doesn’t belong. And compare against your own history, not others — the absolute value differs strongly from person to person.
Use AE as one signal alongside the rest. A gradual rise is encouraging; a dip can come just as easily from a hot day or a short night as from poorer form.
How Trimetra personalises this
Trimetra calculates your aerobic efficiency from comparable easy endurance stimuli and judges the trend against your own baseline, not against a norm. The app accounts for distorting factors and shows AE as a direction over time — one voice in your overall picture, never a standalone grade.
Frequently asked questions
What does a rising aerobic efficiency mean?
That you can handle a higher pace or power at the same heart rate — your engine runs more economically, which points to a growing endurance base. Read it as a trend over weeks though: individual values fluctuate too much to conclude anything per session.
Why does your aerobic efficiency fluctuate so much?
Terrain, wind, heat, fatigue, hydration and sensor noise push your heart rate or pace up or down without you getting fitter or less fit. One dip says little; the direction over a longer period says much more.
Which sessions count for your aerobic efficiency?
Only mutually comparable easy endurance sessions. An interval workout or a ride in full heat doesn’t belong — those distort the ratio. And always compare with your own history, not with others.
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