Karvonen Heart Rate Zones
Why HR reserve beats flat %HRmax for setting training zones.
Karvonen uses heart rate reserve (HRmax − HRrest) to produce zones that scale with fitness — the same 70% intensity shifts higher in BPM as resting HR drops.
Flat %HRmax produces the same zone BPM for a fit runner and an untrained office worker of the same age. That is wrong — the fit runner has a lower resting HR and a wider reserve to spend. Karvonen (1957) fixes this by anchoring zone math to heart rate reserve (HRmax − HRrest) rather than the max alone. As resting HR drops from training adaptation, the computed zone BPM rises, tracking fitness correctly.
Part of: Structural Output
Quick answer
Karvonen uses heart rate reserve (HRmax − HRrest) to produce zones that scale with fitness — the same 70% intensity shifts higher in BPM as resting HR drops.
Key points
- ▸ Formula: zone_bpm = (HRmax − HRrest) × intensity + HRrest. HRmax commonly estimated as 220 − age (±10 bpm population SD).
- ▸ Resting HR must be measured morning, supine, average over 3 days. Caffeine, stress, and poor sleep inflate the number by 5-15 bpm.
- ▸ Zone 1 recovery (50-60% HRR): active recovery, warm-up. Parasympathetic dominant, low fatigue.
- ▸ Zone 2 aerobic (60-70% HRR): base building, fat-oxidation peak, mitochondrial density. The zone endurance pros spend 70-80% of training hours in.
- ▸ Zone 3 tempo (70-80% HRR): aerobic capacity, lactate clearance. Conversational pace fading out.
- ▸ Zone 4 threshold (80-90% HRR): lactate threshold, race pace for 40-90 min events. Uncomfortable, sustainable.
- ▸ Zone 5 VO2max (90-100% HRR): maximal aerobic power. 3-8 min intervals; recovery-expensive.
How to
- Measure resting HR first thing in the morning, supine, for 60 seconds. Average across 3 mornings.
- Estimate HRmax as 220 − age or use a lab / field test for better accuracy.
- Compute HRR = HRmax − HRrest.
- For each intensity %, zone_bpm = HRR × intensity + HRrest. Enter age and resting HR into the calculator to get all five zones.
- Spend ~70-80% of endurance training time in Zone 2, 10-20% in Zone 4-5, fill with Zone 1 recovery.
Examples
- 35 y · HRrest 62HRmax 185 · HRR 123. Z2 aerobic 136-148 bpm · Z4 threshold 160-173 bpm · Z5 VO2max 173-185 bpm.
- 50 y · untrained · HRrest 72HRmax 170 · HRR 98. Z2 131-142 bpm — narrower reserve, slower climb into productive work.
- Same person · post-training-yearHRrest drops from 72 to 58. HRR widens from 98 to 112. Z2 shifts up from 131-142 to 125-139 — the zone is a new BPM band, reflecting new fitness.
When to use which tool
- Operational Heart Rate Zones · KarvonenAny structured cardio program. Re-measure resting HR monthly to keep zones current.Calculate the five training zones using Karvonen (heart-rate reserve) method. More accurate than %HRmax alone.
- Kinetic Expenditure · METPair with MET math to model calorie burn inside each zone.Calories burned per activity using the MET (Metabolic Equivalent of Task) method from the Compendium of Physical Activities.
- CYAN · STABLE — Resting HR under 60 — well-trained cardiovascular system; HRR is wide and Z2 is high.
- GOLD · GUARDED — Resting HR 60-75 — general population healthy range; Karvonen zones scale correctly.
- MAGENTA · CRITICAL — Resting HR over 85 at rest or rising week-over-week — signals overtraining or systemic stress, pull back before pushing zones.
Related
- Operational Heart Rate Zones · KarvonenCalculate the five training zones using Karvonen (heart-rate reserve) method. More accurate than %HRmax alone.
- Kinetic Expenditure · METCalories burned per activity using the MET (Metabolic Equivalent of Task) method from the Compendium of Physical Activities.
- Max Load Capacity · Brzycki 1RMEstimate one-rep maximum from a sub-max set using the Brzycki formula. Recovery / Hypertrophy / Strength zones.
- REM-Sync · Sleep CyclesFind the optimal bedtime or wake time based on 90-minute sleep cycles. Wake at the end of a cycle, not the middle.
- The Karvonen MethodWhy heart rate reserve beats plain %HRmax for zone calculation.
- What Each Heart Rate Zone DoesFat oxidation, lactate, VO2 — the physiology behind the five zones.
- When Heart Rate Zones MisleadCardiac drift, medication, altitude, and stress all break zone accuracy.
Frequently asked questions
› Why Karvonen instead of flat %HRmax? Troubleshooting
Flat %HRmax ignores resting heart rate, which shifts 10-25 bpm across training status. Karvonen anchors on HRR so the same intensity percentage produces the right BPM for a novice and for an elite. It predicts %VO2max far better than %HRmax alone.
› How accurate is 220 − age? How-to
Population estimate with ±10 bpm standard deviation at any given age. Individual HRmax can be 20 bpm off the formula. A ramped field test (5-min all-out finish) or lab VO2max is more accurate if you need tight zones.
› Which zone burns the most fat?
Z2 burns the highest percentage of fat per calorie. Z3-4 burn more absolute fat grams (and more total calories). The "fat-burning zone" framing misleads — total fat oxidation is what matters for body composition, not percentage.
› How should I use this guide with a Kefiw tool? How-to
Use the guide as the plan and the linked Kefiw tool as the check. Read the steps first, try the move manually, then use the tool to compare outputs, catch edge cases, and decide whether the result actually fits your task.
› What mistake do tool guides help avoid? Troubleshooting
Tool guides help avoid using a utility mechanically without understanding what you are trying to accomplish. Most word, writing, and text utilities are fast, but speed can hide context mistakes. Know whether you are solving a puzzle, cleaning copy, drafting a line, or checking a rule.