Your Average Heart Rate Is Lying to You

You finish a training session, check your watch, and feel pretty good about the number staring back at you:

“Average heart rate: 142 bpm.”

Looks good, stayed under the easy day rough cap of 145!

But here's the problem: that number is nearly useless without context.

Average heart rate can be deceiving.

It’s like averaging the temperature of a year and saying, “It was 65°F.”

True, but it tells you nothing about the 100° summer days or 20° winter mornings.

The problem with averages

Heart rate isn't static.

It fluctuates constantly based on what you're doing, how hard you're working, and how recovered you are.

But when you just look at the average, you're missing some of that variance.

That “142 bpm” average could come from:

• 30 minutes at 130 bpm + 10 minutes at 175 bpm
• 40 minutes at a steady 140–144 bpm
• 10 mins at 120–130 bpm, 10 mins at 130–140, 10 mins at 150–160

All of those are completely different workouts, with totally different training effects.

But average HR alone won’t tell you that.

And generally, the shorter the run, the more misleading average HR can be.

A quick example

Let’s say your goal is to keep your heart rate under 145 bpm to stay in Zone 2 and avoid creeping into Zone 3.

You finish your 5-mile run, and your watch says average HR = 142.

You think: “Nice, stayed under the cap.”

But then you check the splits…

• Mile 1: 132 bpm
• Mile 2: 138 bpm
• Mile 3: 147 bpm
• Mile 4: 149 bpm
• Mile 5: 153 bpm

This is what I commonly see with many new clients: steady, sometimes extreme drift.

That average of 142 hid the fact that you actually spent the final 2–3 miles in low Zone 3.

Which means the session wasn’t truly aerobic anymore.

That might be fine if it were intentional, or if it were just for a few minutes.

But if you were aiming for a low-intensity easy run and ended up spending over half the run above your aerobic threshold, you just missed the mark and likely didn’t get the intended adaptation.

*Quick disclaimer: I'm not saying you need to obsessively avoid any drift at all. Or it's not ok to ever go above top-end Z2 on an easy run. Or that you need to massively slow down or walk up every hill to avoid going over the cap. I'm just explaining how only looking at your average HR can be misleading.

If you’re still new to HR training, here’s a primer on why heart rate training is so important for new runners and how to make it work for you.

What to pay attention to instead

Your time in each zone.
Use your heart rate zones to see how much time you actually spent in the intended training zone. If you meant to do a low-intensity ride, but spent 20 minutes in Zone 3… you’re not training what you think you are.

Heart rate trends across the session.
Is your HR drifting up even when pace stays the same? Or are you regularly needing to slow down over the course of a run to keep your HR under the cap? That's generally a sign of poor aerobic fitness and a clear indication that you need to be more strict with keeping your intensity low when your training plan calls for it.

Match HR to power or pace.
Use other data (if available) to assess how efficient your heart is at delivering output. For example, if you're running at a 9:15/mile pace at 145 bpm now, and 2 months ago that same HR required a pace of 10:00/mi, you’ve improved.

Tracking this consistently becomes even more useful when paired with daily readiness data. Here’s how monitoring HRV and resting heart rate (RHR) can give you extra insight into your recovery.

So what should you do?

Stop glancing at the average and calling it a day. Instead:

• Track your time in zones
• Look at HR relative to pace or power
• Watch how your HR responds throughout the workout

These give you far better insight into how your body is adapting and recovering.

Also, I strongly recommend using a chest strap HR monitor. I use this one: Polar H10 Chest Strap.

It's much more accurate and consistent than wrist-worn sensors.

I haven't tried arm band sensors yet, but I have heard good things about them and will likely test one out soon.

Capacity Training

I built Capacity Training to plan your running and your lifting together. Your max heart rate sets your heart-rate zones, and you can import a run from any watch that syncs to Apple Health, with its heart rate, distance and time.

Run faster. Get stronger. capacitytraining.app

Mike