Glossary · Definition

Zone 2 cardio

Zone 2 is sustained low-intensity cardio at roughly 60-70% of max heart rate or heart-rate reserve. Builds mitochondrial density and aerobic base. The cardio zone with the strongest longevity-research backing.

Updated May 2026 · 4 min read

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Definition

What it means

Three definitional methods: Karvonen (uses your resting HR, most personalized), Maffetone (180 - age, conservative), or %max (60-70%). All produce similar zones. The test: you should be able to hold a full conversation in nasal-only breathing while in Zone 2. If you can't, you're going too fast.

Why it matters

Builds mitochondrial density (the cellular engines that determine how well you burn fat at any intensity), lowers resting HR + BP + HbA1c, sustains for 60-90 minutes without crashing recovery. Combined with VO2 max work, Zone 2 is the most-recommended longevity-focused cardio strategy in 2026.

Related free tools

Free toolZone 2 Heart Rate CalculatorCalculate your zone 2 cardio target heart rate using Karvonen, Maffetone (180 - age), or %max-HR methods. The longevity-research-backed cardio range.Open tool →Free toolVO2 Max EstimatorEstimate VO2 max with the Cooper 12-minute run, Rockport 1-mile walk test, or resting heart rate method. Plus age + sex norms for context.Open tool →

Frequently asked questions

How much per week?

30-90 min, 2-4×/week. Less than 30 min isn't the same dose.

Walking, running, cycling?

Any modality. Walking only counts if it actually gets you into the heart rate zone.

Related terms

DefinitionVO2 maxVO₂ max is the maximum oxygen your body can use during exercise, in ml/kg/min. The strongest single fitness correlate of all-cause mortality — going from 'poor' to 'average' is the biggest single health investment most adults can make.