The Zone 2 Hype: More Than Just a Number

We recently explored the hype and the misconceptions surrounding zone 2 training. It's a topic that continues to divide opinion, especially now that Strava has introduced a new feature: heart rate training zones.

That makes it the perfect time to revisit the topic. We dive deeper into how data, when misinterpreted, can send your training in the wrong direction.

What Zone 2 Really Means

In our previous blog, we explained that true zone 2 isn’t just a heart rate range. It reflects a metabolic state, namely your first lactate threshold (LT1).

Ideally, we define heart rate zones via lactate testing, because your intensity drives your heart rate, but your heart rate doesn't define your intensity. That’s why, as coaches, we always interpret heart rate data in context and never in isolation.

Strava's New Feature: HR Zones Based on Max Heart Rate

Strava’s introduction of training zones gives insight into how they structure heart rate data. Yes, users can adjust zones manually, but most will stick with the default.

And that default? Strava defines zone 2 as 66% to 81% of your maximum heart rate.
That’s a very broad range. For many runners, especially recreational or even advanced runners, the upper end (81% of HRmax) is well into zone 3 or even tempo intensity.

Why Strava’s “Zone 2” Might Be Too High and Risky

The danger is that this zone feels easy enough. and Strava confirms it as an “easy” session. You think:
“I’m training smart. I’m building my base. Strava says so.”. But in reality, if you’re training near that upper limit, your physiological stress is far higher than intended. That undermines your aerobic base and exposes you to another risk: chronic stress.

I saw someone put it this way:

“Those high (way too high) Z2 produces a load of skinny-fat runners due to cortisol.”

It’s an oversimplification, but not entirely wrong. Training too hard too often, even when it “feels easy,” leads to chronically elevated cortisol. That means:

• You burn more carbs than fat

• You may lose weight, but also muscle and water

• Your body fat percentage doesn’t drop and may even rise

• Cravings increase, fat storage is promoted

That’s not base training. That’s overreaching in disguise.

Why Trenara Does It Differently

We don’t base our training zones on max heart rate. Instead, we use your actual performance, converted into a virtual VO₂max, to define your zones.

Why? Because your race performance is real data and your estimated HRmax often isn’t.

Our zone 2 is more conservative by design. We set a lower upper limit, and then further personalize it based on your performance capacity. That system has been in place for about six months now, and this current racing season is the first to show its benefits.

Popular ≠ Proven

We’re not saying Strava’s data is useless. But popularity doesn’t equal accuracy. And what’s popular isn’t always what’s scientifically validated or proven in the field. Strava’s goal is engagement, not performance optimization. Their algorithm won’t tell you when your training intensity is too high. Ours will, albeit it may be confrontational.

At Trenara, we take our role seriously. You’re trusting us with your training. And that means:

• Prioritizing your health

• Grounding our methods in physiology

• Helping you run smarter and not just harder

Because training well isn’t about chasing likes. It’s about building fitness for life. Maybe we should show off our fancy stats better.