Heart Rate Zones on WHOOP: Why WHOOP Uses Heart Rate Reserve (HRR)

WHOOP sets five personalized heart rate zones using the heart rate reserve (HRR) method, which factors in both your maximum heart rate and your current resting heart rate. This is different from the age-based maximum heart rate (HRmax) formula many trackers default to, and the difference is the reason WHOOP zones look the way they do.

The HRR method, also called the Karvonen method, was developed by Finnish physiologist Martti Karvonen in the 1950s and is widely used in exercise physiology because it adapts to your individual fitness. As your resting heart rate drops with training, your WHOOP zones shift to match the cardiovascular system you have today, not the one you had a year ago.

What is the heart rate reserve (HRR) method?

Heart rate reserve is the range between your resting heart rate (RHR) and your maximum heart rate (HRmax). The Karvonen formula uses that range to calculate the target heart rate for a given exercise intensity:

Target HR = ((HRmax − RHR) × % intensity) + RHR

The output is a heart rate value calibrated to your physiology, not a population average. Two members the same age can have very different HRR ranges; their training zones will look very different as a result.

HRR vs. maximum heart rate: how the two methods differ

The two methods answer the same question (what counts as moderate vs. vigorous exercise for me?) with different math.

• What each uses: The HRR method uses your HRmax and your resting heart rate. The % HRmax method uses your HRmax only.
• How it accounts for fitness: HRR adjusts as your RHR changes with training. % HRmax does not adjust for cardiovascular fitness.
• Effort at the same zone label: HRR reflects the intensity you actually feel. % HRmax tends to underestimate effort for fit individuals and overestimate it for unfit individuals.
• Who developed it: HRR comes from Martti Karvonen in the 1950s. % HRmax comes from various age-prediction equations such as 220 minus age.
• Used by WHOOP: HRR is the default. % HRmax is available via manual override.

The practical effect: an HRR-based Zone 2 prescribes the same relative effort for a beginner and a competitive cyclist, even though their absolute heart rate numbers are very different. A % HRmax Zone 2 gives both people the same heart rate target, which usually undershoots the trained athlete and overshoots the beginner.

How WHOOP calibrates your zones to your fitness

WHOOP uses a rolling 14-day resting heart rate baseline. As that baseline drops with training, your HRR range widens, and every zone shifts up to reflect the cardiovascular work you can now sustain. Members who improve over a training block see their zones move with them, no manual update required.

The starting maximum heart rate is estimated from age and refined over time from observed workout data. If you have a lab-measured HRmax from a VO2 max test, you can override the estimate manually (see the section below).

The five WHOOP heart rate zones

WHOOP applies the HRR method to a five-zone model. The percentages below are the standard HRR ranges; the absolute heart rate values are personalized to every member based on their own RHR and HRmax. Your live cutoffs appear in the app at More → App Settings → Activity Settings → Heart Rate Settings.

• Zone 1 (40 to 60% of HRR): Very light activity and active recovery
• Zone 2 (60 to 70% of HRR): Light to moderate physical activity, the aerobic base zone
• Zone 3 (70 to 80% of HRR): Moderate activity, aerobic exercise
• Zone 4 (80 to 90% of HRR): Vigorous activity, anaerobic exercise
• Zone 5 (90 to 100% of HRR): Maximum effort, very high-intensity anaerobic exercise

For a deeper look at why Zone 2 is the foundation of cardiovascular training, see Why Zone 2 Training Is the Secret to Unlocking Peak Performance.

How heart rate zones connect to Healthspan and WHOOP Age

WHOOP Age is part of the Healthspan feature and estimates your physiological age relative to your chronological age. The model is calibrated against HRR-based intensity, which is why changing your zone method (HRR to % HRmax, or vice versa) can shift your WHOOP Age. The two methods are not interchangeable inputs.

The research case is direct. The WHOOP Healthspan whitepaper (p.23) cites studies linking 5 to 7 hours of weekly physical activity to a 20% to nearly 50% reduction in all-cause mortality, with objective tracking from wearables showing even stronger associations. Even short doses count: just 15 to 20 minutes of vigorous exercise per week, broken into 1 to 2 minute bursts, has been associated with an 18 to 24% lower risk of all-cause mortality compared to no vigorous activity at all. Those associations are what make Zone Time a load-bearing input to WHOOP Age. (For the full methodology and citations, see the WHOOP Healthspan whitepaper.)

WHOOP translates that research into specific weekly Zone Time targets. For young adults, WHOOP recommends at least 100 minutes per week in Zones 1 to 3 and at least 10 minutes per week in Zones 4 to 5 to see a reduction in WHOOP Age. Additional activity provides incremental benefit up to roughly 600 minutes per week. Targets decrease slightly as members age, in line with research showing the longevity benefits of activity grow with age.

If you change your zone calculation method or manually move your HRmax, expect your WHOOP Age to move too. The model is calibrated against HRR; swapping the input changes the output. That is the model working as designed.

Manually adjusting your max HR and zone boundaries

If you have a lab-tested HRmax (from a VO2 max test, ramp test, or similar) or you prefer % HRmax over HRR, you can override the defaults.

In the WHOOP app: More → App Settings → Activity Settings → Heart Rate Settings. From there you can set your max HR, choose the calculation method, and customize the zone boundaries. Changes apply going forward; historical activities are not recalculated.

Frequently asked questions about heart rate zones on WHOOP

Why do my WHOOP zones look different from zones I have seen elsewhere? Most public training plans and many devices default to the % HRmax method. WHOOP uses HRR (Karvonen), which factors in resting heart rate as well as max. Two methods, two sets of numbers, same underlying physiology. Neither is wrong; they are calibrated differently.

Does WHOOP use the Karvonen formula? Yes. WHOOP zones are calculated with HRR, which is the same method commonly referred to as the Karvonen formula in exercise physiology.

Will changing my max HR or zone method change my WHOOP Age? Yes. WHOOP Age is calibrated using HRR-based intensity. Switching to a % HRmax model or moving your max HR changes the input to the model, so the output changes. Expect a shift if you adjust either setting.

How often does WHOOP recalculate my zones? WHOOP uses a rolling 14-day resting heart rate baseline, so your zones adapt as your RHR moves. There is no manual refresh required.

Can I see the exact heart rate cutoffs for my zones? Yes. Open the WHOOP app and tap More → App Settings → Activity Settings → Heart Rate Settings. Your personalized cutoffs are listed by zone.

How much time should I spend in each zone per week? WHOOP recommends at least 100 minutes per week in Zones 1 to 3 and at least 10 minutes per week in Zones 4 to 5 for young adults to see a reduction in WHOOP Age. Benefits accrue incrementally up to about 600 minutes per week. Targets ease slightly with age. The full rationale is in the Healthspan whitepaper, p.23.

Key takeaways

• WHOOP uses the heart rate reserve (HRR) method, also called the Karvonen formula, which factors in both your maximum heart rate and your resting heart rate
• HRR adapts to your fitness over time; % HRmax does not
• The five zones are 40 to 60% (Zone 1), 60 to 70% (Zone 2), 70 to 80% (Zone 3), 80 to 90% (Zone 4), and 90 to 100% (Zone 5) of HRR
• WHOOP Age is calibrated against HRR-based intensity, so changing your zone method will shift your WHOOP Age
• For young adults, WHOOP recommends at least 100 minutes per week in Zones 1 to 3 and at least 10 minutes per week in Zones 4 to 5 to see a reduction in WHOOP Age
• Personalized cutoffs live at More → App Settings → Activity Settings → Heart Rate Settings