Zone 2 Training

Low-intensity aerobic work at 60–70% max heart rate. Builds fat-burning efficiency and mitochondrial density.

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Understanding Zone 2 Training

Zone 2 training refers to running at 60–70% of your maximum heart rate — an intensity that feels easy and conversational. It's the intensity where your body primarily burns fat for fuel and develops the aerobic base that underpins all endurance performance.

The renewed interest in Zone 2 comes from exercise physiologists like Dr. Iñigo San Millán, who showed that training at this specific intensity maximally develops mitochondria (the cell's energy factories) and improves fat oxidation rates. Elite endurance athletes spend 75–80% of their training time in Zone 2 — the "Norwegian method" that has produced world-class results.

For most recreational runners, Zone 2 feels uncomfortably slow. Your ego will resist it. But this is where the magic happens: capillaries grow, mitochondria multiply, and your body becomes more efficient at using fat as fuel — sparing glycogen for when you actually need it in races. The athletes who embrace easy running get faster; those who run every workout hard plateau and get injured.

Key Facts: Zone 2 Training

Key facts and insights about zone 2 training that every endurance athlete should know.

Zone 2

Zone 2: 60–70% of max heart rate, or conversational pace

Elite runners spend 75–80% of training v

Elite runners spend 75–80% of training volume in Zone 2

Primary adaptation

Primary adaptation: increased mitochondrial density and fat oxidation

Dr. Iñigo San Millán's research on Zone

Dr. Iñigo San Millán's research on Zone 2 has influenced modern training methodology

Pro Tips: Zone 2 Training

Use a heart rate monitor to keep yourself honest — pace alone can be misleading on hilly or hot days

If you can't maintain a conversation, you're above Zone 2 — slow down

Run by time rather than distance in Zone 2 to remove the pressure to hit a pace

It takes 4–8 weeks of consistent Zone 2 training before you notice your easy pace getting faster at the same heart rate

Frequently Asked Questions About Zone 2 Training

Because most runners habitually train too fast. If you've been running at Zone 3–4 for years, true Zone 2 will feel painfully slow. This is normal. As your aerobic base develops over weeks and months, your Zone 2 pace will naturally get faster. Trust the process.

The simplest method: estimate max heart rate (220 - age, or better, from a max effort test) and calculate 60–70% of that. For a 40-year-old with estimated max HR of 180, Zone 2 is 108–126 bpm. A lab test (metabolic cart) gives the most accurate zones, but the talk test works too: if you can comfortably speak in full sentences, you're likely in Zone 2.