Heart-Rate Zones vs Zone 2 Tools: Two Maps of the Same Effort

"Zone 2" means different things to different tools. Running both engines on the same athlete shows the Karvonen 5-zone band (136–150) and the Maffetone band (140–150) share a ceiling and differ only at the floor, while the lactate-threshold method draws a markedly lower band (125–141). The practical question is which ceiling to hold for aerobic-base work. This is the decision-frame entry in our Zone 2 series: rather than surveying the evidence, it runs both engines on the same person and resolves where to draw the line.

Engine outputs

A 30-year-old athlete with a 55 bpm resting HR, through the five-zone Heart Rate Zone Calculator (Karvonen) and the four-method Zone 2 Heart Rate Calculator:

# heart-rate-zone-calculator (computed live from /engines/heart-rate-zone-calculator.js)
Engine input
  age                   = 30
  resting_hr            = 55

Engine output
  maxHr                 = 190
  hrr                   = 135
  zones[0].zone         = Zone 1 (Recovery)
  zones[0].lowBpm       = 123
  zones[0].highBpm      = 136
  zones[1].zone         = Zone 2 (Endurance)
  zones[1].lowBpm       = 136
  zones[1].highBpm      = 150
  zones[2].zone         = Zone 3 (Tempo)
  zones[2].lowBpm       = 150
  zones[2].highBpm      = 163
  zones[3].zone         = Zone 4 (Threshold)
  zones[3].lowBpm       = 163
  zones[3].highBpm      = 177
  zones[4].zone         = Zone 5 (VO2 Max)
  zones[4].lowBpm       = 177
  zones[4].highBpm      = 190

# zone-2-heart-rate-calculator (computed live from /engines/zone-2-heart-rate-calculator.js)
Engine input
  age                   = 30
  resting_hr            = 55
  methods[0]            = maffetone
  methods[1]            = percentage
  methods[2]            = karvonen
  methods[3]            = lactate

Engine output
  methods[0].key        = maffetone
  methods[0].label      = Maffetone (MAF 180)
  methods[0].zone2Low   = 140
  methods[0].zone2High  = 150
  methods[0].maxHr      = 180
  methods[0].maxHrLabel = MAF base: 150 bpm
  methods[0].zones[0].zone= Zone 1 (Recovery)
  methods[0].zones[0].lowBpm= 120
  methods[0].zones[0].highBpm= 130
  methods[0].zones[1].zone= Zone 2 (Aerobic Base)
  methods[0].zones[1].lowBpm= 140
  methods[0].zones[1].highBpm= 150
  methods[0].zones[2].zone= Zone 3 (Tempo)
  methods[0].zones[2].lowBpm= 151
  methods[0].zones[2].highBpm= 160
  methods[0].zones[3].zone= Zone 4 (Threshold)
  methods[0].zones[3].lowBpm= 161
  methods[0].zones[3].highBpm= 170
  methods[0].zones[4].zone= Zone 5 (VO2 Max)
  methods[0].zones[4].lowBpm= 171
  methods[0].zones[4].highBpm= 180
  methods[0].recommended= false
  methods[0].requiresRhr= false
  methods[0].note       = Simple age-based formula popularized by Dr. Phil Maffetone. No equipment needed. Best for beginners and low-HR base training.
  methods[1].key        = percentage
  methods[1].label      = % of Max HR (estimated)
  methods[1].zone2Low   = 114
  methods[1].zone2High  = 133
  methods[1].maxHr      = 190
  methods[1].maxHrLabel = Traditional: 190 bpm / Tanaka: 187 bpm
  methods[1].zones[0].zone= Zone 1 (Recovery)
  methods[1].zones[0].lowBpm= 95
  methods[1].zones[0].highBpm= 114
  methods[1].zones[1].zone= Zone 2 (Aerobic Base)
  methods[1].zones[1].lowBpm= 114
  methods[1].zones[1].highBpm= 133
  methods[1].zones[2].zone= Zone 3 (Tempo)
  methods[1].zones[2].lowBpm= 133
  methods[1].zones[2].highBpm= 152
  methods[1].zones[3].zone= Zone 4 (Threshold)
  methods[1].zones[3].lowBpm= 152
  methods[1].zones[3].highBpm= 171
  methods[1].zones[4].zone= Zone 5 (VO2 Max)
  methods[1].zones[4].lowBpm= 171
  methods[1].zones[4].highBpm= 190
  methods[1].recommended= false
  methods[1].requiresRhr= false
  methods[1].note       = Zone 2 = 60-70% of max HR. Max HR estimated via 220-age (190) and Tanaka 208-0.7x age (187).
  methods[2].key        = karvonen
  methods[2].label      = Karvonen (Heart Rate Reserve)
  methods[2].zone2Low   = 136
  methods[2].zone2High  = 150
  methods[2].maxHr      = 190
  methods[2].maxHrLabel = HRR: 135 bpm
  methods[2].zones[0].zone= Zone 1 (Recovery)
  methods[2].zones[0].lowBpm= 123
  methods[2].zones[0].highBpm= 136
  methods[2].zones[1].zone= Zone 2 (Aerobic Base)
  methods[2].zones[1].lowBpm= 136
  methods[2].zones[1].highBpm= 150
  methods[2].zones[2].zone= Zone 3 (Tempo)
  methods[2].zones[2].lowBpm= 150
  methods[2].zones[2].highBpm= 163
  methods[2].zones[3].zone= Zone 4 (Threshold)
  methods[2].zones[3].lowBpm= 163
  methods[2].zones[3].highBpm= 177
  methods[2].zones[4].zone= Zone 5 (VO2 Max)
  methods[2].zones[4].lowBpm= 177
  methods[2].zones[4].highBpm= 190
  methods[2].recommended= true
  methods[2].requiresRhr= false
  methods[2].note       = Most individualized method. Uses resting HR to calculate heart rate reserve. Preferred when RHR is known.
  methods[3].key        = lactate
  methods[3].label      = Lactate Threshold Estimate
  methods[3].zone2Low   = 125
  methods[3].zone2High  = 141
  methods[3].maxHr      = 190
  methods[3].maxHrLabel = Est. LTHR: 166 bpm
  methods[3].zones[0].zone= Zone 1 (Recovery)
  methods[3].zones[0].lowBpm= 108
  methods[3].zones[0].highBpm= 125
  methods[3].zones[1].zone= Zone 2 (Aerobic Base)
  methods[3].zones[1].lowBpm= 125
  methods[3].zones[1].highBpm= 141
  methods[3].zones[2].zone= Zone 3 (Tempo)
  methods[3].zones[2].lowBpm= 141
  methods[3].zones[2].highBpm= 158
  methods[3].zones[3].zone= Zone 4 (Threshold)
  methods[3].zones[3].lowBpm= 158
  methods[3].zones[3].highBpm= 166
  methods[3].zones[4].zone= Zone 5 (VO2 Max)
  methods[3].zones[4].lowBpm= 167
  methods[3].zones[4].highBpm= 190
  methods[3].recommended= false
  methods[3].requiresRhr= false
  methods[3].note       = Lactate threshold HR estimated at 87.5% of max HR (166 bpm). Zone 2 = 75-85% of LTHR. Best accuracy requires lab testing.
  estimatedMaxHrTraditional= 190
  estimatedMaxHrTanaka  = 187
  hasRhr                = true
  hasCustomMaxHr        = false

The Karvonen method computes percentages of heart-rate reserve (HRR = max − resting), then adds resting back to produce absolute bpm targets. Max HR comes back at 190 bpm and HRR at 135; the five named zones run 123–136 (Recovery), 136–150 (Endurance/Zone 2), 150–163 (Tempo), 163–177 (Threshold), and 177–190 (Max).^[1]

On the dedicated Zone 2 engine, the Maffetone method sets the Zone 2 ceiling at 180 − age = 150 bpm, with a floor at 140. The engine's Karvonen method returns 136–150 — identical ceiling to the 5-zone engine, as expected since both use the same HRR math. The percentage-of-max method runs lower (114–133) because it caps Zone 2 at 70% of the estimated maximum. The lactate-threshold method is the conservative one: it estimates LTHR at 166 bpm and sets Zone 2 at 125–141.^[3]

Where the methods disagree

The 5-zone engine and the Maffetone method share the same Zone 2 ceiling: 150 bpm. The Karvonen Zone 2 (136–150) and Maffetone Zone 2 (140–150) differ only by 4 bpm at the floor. The genuine outlier is the lactate-threshold method, whose ceiling of 141 bpm sits 9 bpm below the other two — that is where the meaningful disagreement lives.

Seiler's published polarised-training research found that recreational athletes who train in the 70–80% HRR band (the upper end of the 5-zone "Zone 2") gain less aerobic adaptation per hour than athletes who train either lower (60–70% HRR, true polarised easy work) or higher (above 85% HRR, true threshold/interval work). The 80/20 distribution Seiler proposed explicitly excludes the upper-Zone-2 / lower-Zone-3 band — which, for this athlete, is exactly the 141–150 bpm slice that separates the lactate-threshold ceiling from the Maffetone/Karvonen ceiling.^[2]

What the 5-zone engine is good for

The Karvonen 5-zone framework is the right tool for prescribing all training intensities, not just easy work. Tempo, threshold, and VO2-max sessions need explicit zone targets, and the percentage-of-HRR mapping produces clean, individualised numbers for each session type.

Where it underperforms: for athletes whose primary need is high aerobic volume in true Zone 2, the wider band lets them drift into the no-man's-land territory and waste training stimulus.

What the Zone 2 / Maffetone engine is good for

Dedicated Zone 2 tools are anchored on lactate-threshold proxies rather than HRR percentages. The Maffetone 180-minus-age formula approximates the aerobic-anaerobic transition — the heart rate at which lactate accumulation begins. Holding training below that ceiling maximises mitochondrial adaptation per hour of low-intensity work.^[3]

Where it underperforms: as a global zone framework. Maffetone's higher zones are crude offsets above the MAF base rather than HRR-individualised targets; athletes prescribing real threshold or VO2-max sessions are better served by the Karvonen 5-zone output for higher-intensity work.

How they disagree

1. Anchor: 5-zone uses max HR and HRR. Zone 2 tools use lactate-threshold approximations.
2. Method assumption: 5-zone assumes a percentage-of-reserve relationship to physiological intensity. Zone 2 tools assume the LT-derived ceiling is the load-bearing parameter.
3. Granularity: 5-zone produces five named zones. Zone 2 tools focus on one zone with a hard ceiling.

When to use which

1. For aerobic-base building (3–6 month focused block): The conservative lactate-threshold ceiling (141 bpm here) is the safest anchor. Stay below it for 80% of weekly volume; if you prefer the Maffetone/Karvonen band, hold the floor (140 bpm) rather than drifting to the 150 ceiling.
2. For prescribing tempo / threshold / VO2-max sessions: The 5-zone Karvonen output is the right tool. Use Zone 4 (163–177 bpm) for threshold, Zone 5 for intervals.
3. For mixing both: Use the Zone 2 ceiling as the upper bound on easy days, the 5-zone bands for hard days. This is the practical polarised workflow.
4. For the most conservative easy-day cap: the lactate-threshold method (141 bpm here). It is the only one of the four that pulls the ceiling meaningfully below 150.

The Resting Heart Rate Calculator is the prerequisite measurement for the Karvonen method, which uses resting HR to compute heart-rate reserve. The Maffetone (180 − age) method does not require resting HR at all — handy when you don't have a reliable morning measurement. Measurement protocol for Karvonen: morning, fasted, before standing, averaged over 7 days.

The "no man's land" intensity

Seiler's polarised-training papers coined the term "no man's land" for the intensity band that sits above true aerobic-base work but below the lactate-threshold trigger — roughly 75–82% of HRR for trained athletes. For this athlete that is the 141–150 bpm slice: above the lactate-threshold method's ceiling (141) but still inside the Karvonen and Maffetone "Zone 2" bands, which both run up to 150.^[2]

The no-man's-land effect is well documented: training in this band produces enough cardiovascular load to feel productive but not enough metabolic adaptation per hour to justify the recovery cost. Athletes who accumulate weekly hours in this band typically plateau in aerobic development after 6–8 weeks, despite the time investment feeling significant.

Practical consequence: the lactate-threshold ceiling (141 bpm here) sits below the no-man's-land boundary on purpose. The Maffetone and Karvonen "Zone 2" ceilings (150 bpm) reach into the no-man's-land. For an athlete trying to build aerobic base, the lower ceiling produces better outcomes per hour even though all three are labelled "Zone 2."

Across a typical 6-hour easy-volume week, the difference between the 141 and 150 ceilings compounds into roughly 30–45 minutes of potentially misallocated training time — significant over a 12-week aerobic block.

Cross-checking against related tools

The Heart Rate Zone Calculator exposes both Karvonen and percentage-of-max methods side-by-side. The Zone 2 Heart Rate Calculator includes four methods: Maffetone (MAF 180), percentage-of-max, Karvonen (HRR), and a lactate-threshold estimate. The VO2 Max Estimator adds the field-test cross-check to validate that the zones map onto actual physiological intensity.

Related in this series

• Zone 2 Training: What the Literature Says — the literature pillar on dose-response and the polarised-training framing.
• Zone 2: Methods and Limits — how each method defines the zone and where the measurement breaks down.
• Zone 2 HR for a 30-Year-Old, RHR 50 — worked case running all four methods on one athlete.

Beyond the series: Heart Rate Zones: Methods Compared is the full HR-method survey, and How To Use Heart Rate Zones covers session-by-session implementation.

FAQ

The methods disagree on Zone 2 — which do I follow?

For aerobic-base sessions, follow the lower ceiling. Here the lactate-threshold method caps Zone 2 at 141 bpm, 9 bpm below the Maffetone and Karvonen ceiling of 150. The published trial data on polarised training is unambiguous that the conservative ceiling produces better aerobic adaptation per hour than letting easy work creep toward the 150 cap.^[2]

Is Karvonen better than percentage-of-max?

For most athletes, yes. Karvonen accounts for resting heart rate, which varies by fitness level; percentage-of-max ignores it. The difference matters most for fit athletes with low resting HRs — they end up with higher absolute targets under Karvonen, which match their physiology better.

What if my max HR isn't 190?

The Tanaka formula has ±10 bpm individual variation. If your tested max HR (from a true maximal effort) differs from 190 by more than 8 bpm, use the tested number as the input rather than the formula prediction. The engine accepts a custom max-HR input.^[1]

Is Maffetone too conservative?

For competitive athletes preparing for events, possibly. The 180-minus-age formula was originally derived for general health and recreational endurance. Competitive athletes often use a lactate-threshold-test-derived ceiling 5–10 bpm higher than Maffetone's. The dedicated Zone 2 engine supports both methods.