Running Efficiency: How to Read Your Efficiency Factor
Running efficiency answers a simple question: how much distance do you cover per heartbeat? Two runners can hold the same pace, but the one whose heart beats slower to do it has the more efficient aerobic engine — and, usually, the more trainable one.
We track it as the Efficiency Factor (EF): your running speed in metres per minute divided by your average heart rate during a steady aerobic run.
What it measures
EF = speed (m/min) ÷ average heart rate (bpm).
A higher number means your body delivers and uses oxygen more economically: more metres covered for each beat. Because it pairs output (speed) with cost (heart rate), EF captures aerobic fitness, running economy, and cardiac efficiency in a single ratio. It is closely related to the "Efficiency Factor" popularised by coach Joe Friel for endurance training.
How to measure it
- Run at a steady, conversational aerobic pace for at least 10 minutes (after a short warm-up). Flat ground, no intervals, no hills.
- Record your average pace (minutes per km) and average heart rate (bpm) for the steady portion.
- Convert pace to speed and divide by heart rate:
speed (m/min) = 60000 ÷ pace-in-seconds-per-km EF = speed (m/min) ÷ average HR
For example, 5:00/km (300 s/km) is 200 m/min; at 150 bpm that's an EF of 1.33. Pick up to 4:00/km (240 s/km → 250 m/min) at the same 150 bpm and EF rises to 1.67.
A rough orientation table
These bands are a rough orientation, not an authoritative standard — the ranges below are our editorial adaptation of the Efficiency Factor concept, not published cut-offs. EF depends heavily on your maximum heart rate, terrain, heat, hydration, and how rested you are — so treat the table as a ballpark, and read the next section before comparing yourself to anyone else.
| Level | Approx. EF (m/min per bpm) | What it reflects |
|---|---|---|
| Recreational | ~1.0–1.4 | New or occasional runners; aerobic base still developing |
| Trained | ~1.4–1.8 | Regular runners with a solid aerobic base |
| Competitive | ~1.8–2.1 | Experienced runners training structured volume |
| Elite | > 2.1 | Highly trained endurance athletes |
Why it's an individual number
EF is most useful compared against yourself, not against a table. Your maximum heart rate is largely genetic, so two equally fit runners can have very different EF values purely because one has a higher HR ceiling. Heat, humidity, altitude, caffeine, poor sleep, and accumulated fatigue all push heart rate up and EF down on a given day — without your fitness actually changing.
The signal that matters is the trend: as your aerobic base improves, your EF at the same easy pace drifts upward over weeks and months. A rising EF at a fixed pace is one of the cleanest indicators that base training is working ("aerobic decoupling" in reverse).
How to improve it
- Build the aerobic base. Most of your running should be easy, conversational "zone 2" effort (roughly 60–70% of your maximum heart rate). This is what raises mitochondrial density and stroke volume — the machinery EF measures.
- Be consistent. EF responds to weeks of steady volume, not single hard sessions.
- Add some intensity, sparingly. One or two harder sessions a week (intervals, tempo) lift the ceiling, but the base does most of the work for EF.
- Test under similar conditions. Compare EF from runs at similar temperature, terrain, and freshness so you are measuring fitness, not the weather.
Sources & further reading
- Joe Friel, The Triathlete's Training Bible / TrainingPeaks — origin of the Efficiency Factor (EF) and its use for tracking aerobic fitness over a season.
- Running-economy literature (e.g. Saunders et al., Sports Medicine, 2004) on the determinants of how economically trained runners use oxygen.