What is Zone 2 training?

Zone 2 is the moderate, sustainable intensity where your body relies mainly on fat oxidation and stays below the first lactate threshold. Popularised for endurance by Inigo San Millan, it drives mitochondrial growth and aerobic efficiency, and you should be able to hold a conversation throughout.

Which method is more accurate?

The lactate-threshold method is more individual because it anchors to your real physiology. Zone 2 sits at roughly 80 to 88 percent of LTHR. The reserve method estimates the same band from resting and max HR and is a good fallback when you lack threshold data.

How do I find my lactate threshold heart rate?

A common field estimate is the average heart rate of a hard, steady 30-minute time trial (using the last 20 minutes). A lab lactate test or a ramp test on a trainer gives a more precise figure. Use whichever you have for the threshold method.

What is heart-rate reserve?

Heart-rate reserve is your max HR minus your resting HR — the range you can raise your heart rate over. The Karvonen method takes a percentage of that reserve and adds it back to resting HR, which personalises the zone better than a flat percentage of max.

Why does it feel too easy?

That is the point. Zone 2 should feel almost frustratingly easy because the benefit comes from time spent there, not effort. If you cannot hold a conversation or your pace drifts up, you have drifted out of Zone 2 and into tempo work.

Zone 2 Heart Rate Calculator

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Zone 2 is the aerobic base zone where fat oxidation and mitochondrial adaptation peak. This calculator finds your personal Zone 2 heart-rate band either from your lactate-threshold heart rate or from resting and max HR using the heart-rate reserve method.

How it works

Two methods are available:

Threshold method:  Zone 2 = 80% to 88% of LTHR
Reserve (Karvonen): HRR = maxHR − restingHR
                    target = restingHR + pct × HRR
                    Zone 2 ≈ 60% to 70% of HRR

The threshold method anchors directly to your physiology, so it is preferred when you know your LTHR. The reserve method personalises a percentage band using your full working heart-rate range rather than a flat share of max HR.

Notes

Zone 2 should feel easy enough to hold a conversation — the benefit comes from accumulated time, not intensity. If pace creeps up or talking gets hard, you have drifted into tempo. Recalculate as your resting HR, max HR, or threshold change with fitness.