posted 14th March 2026
At Infinite Endurance Coaching, we believe in being scientifically driven and athlete-first. One of the most powerful metrics we use to track your progression is Aerobic Efficiency. It tells us the "cost" of your speed—specifically, if you are running faster for the same heart rate (HR) or maintaining the same pace with a lower HR.
If you use Training Peaks or Garmin, you already have the data; you just need to know where to look. Here is your technical how-to guide to mastering your metrics.
Understanding the Goal
To get a clean Aerobic Efficiency metric, you need a "control" run. We recommend using a fixed benchmark route performed at a steady, conversational intensity (Zone 2). This ensures that any changes in the data are due to fitness gains rather than varying efforts.
How to Find Aerobic Efficiency in Training Peaks
Training Peaks automates this through a metric called Efficiency Factor (EF). EF is calculated by taking your Normalised Pace (or Power) and dividing it by your Average Heart Rate.
Step-by-Step Guide for TrainingPeaks :
- Log In: Open your Training Peaks account and select a completed "Steady State" or Zone 2 run.
- Open the Workout: Click on the specific workout to open the detailed summary.
- Locate the Summary Block: Look at the right-hand sidebar (on a desktop) or the "Summary" tab (on mobile).
- Find "EF": Under the "Completed" stats, you will see EF.
- The Analysis: Compare the EF of today's run to a similar run from four weeks ago. A higher EF number means you are becoming more efficient—you are producing more "output" (pace) for every "input" (heartbeat).
How to Track Aerobic Efficiency in Garmin Connect
Garmin doesn't provide a single "EF" number, but it allows you to visualize the relationship between pace and heart rate through its graphing and lap tools.
Step-by-Step for Garmin Connect:
- Open Garmin Connect: Select your benchmark run from your activity list.
- Analyse the Laps: Go to the "Laps" tab. Compare your Average Pace and Average Heart Ratefor each mile.
- Sign of improvement: Your pace is consistent across laps, but your heart rate is lower than in previous months.
- Check the Overlays: On the desktop version, go to the "Charts" section and use the Overlays feature. Select both "Heart Rate" and "Pace."
- What to look for: Look for "decoupling." If your heart rate line stays flat while your pace stays flat, you are aerobically efficient. If the heart rate line starts to drift upward while pace stays the same, you are experiencing fatigue.
- Performance Condition: Keep an eye on the "Performance Condition" pop-up on your watch during the first 6–20 minutes of a run. This is Garmin’s real-time estimate of your efficiency compared to your baseline.
Summary of Indicators: Are You Getting Faster?
| Metric | Sign of Improvement | Sign of Poor Repeatability |
|---|---|---|
| Pace at Given HR | Faster pace for the same HR | Slower pace for the same HR |
| HR at Given Pace | Lower HR for the same pace | Higher HR for the same pace |
| RPE | The same pace feels easier (lower RPE) | The same pace feels harder (higher RPE) |
Stop Guessing, Start Executing
Data is only valuable if it leads to better judgement. While these metrics help you see the "What," a coach helps you understand the "How" and the "Why".
If your Aerobic Efficiency has plateaued, or if your heart rate is spiking higher for the same effort, your body is telling you something. At IEUK Coach, we help you pivot your strategy to manage fatigue and unlock your next level of performance.
Ready for a deep dive into your own data?
[Book a free 15-minute consultation at IEUK Coach today and discuss your upcoming race plan]. Contact Us page I'll build a performance strategy in the context of your life that actually moves the needle.
Infinite Endurance Coaching: Sustainable Performance. Data Driven. Athlete-First.
