Heart-Rate Zones and Your Real HRmax

Every zone chart you've ever seen, the gym-wall poster, the treadmill sticker, your watch's colored arcs, is built on one number: your maximum heart rate. Get that number wrong and every zone under it is wrong by the same amount. This article covers what the zones actually mean, why the formula everyone uses misses badly for a lot of people, and how RepTrack resolves your real HRmax.

The five zones, in plain language

RepTrack bands your workout heart rate into zones cut at 50 / 60 / 70 / 80 / 90 percent of your HRmax:

• Below 50%, Rest. Not training; recovery, standing around, walking to the rack.
• 50–60%, Warm-up. Blood flowing, joints moving. Where warm-ups and cool-downs should live.
• 60–70%, Fat burn. The classic easy-aerobic band: conversational pace, sustainable for a long time. (The name is historical, you burn a higher fraction of fat here, not necessarily more fat overall.)
• 70–80%, Cardio. The aerobic engine room. Tempo runs, brisk intervals, most "moderate-hard" endurance work.
• 80–90%, Peak. Threshold and interval territory. Hard to hold, and that's the point.
• 90%+, Max. Sprint finishes and final reps. Visits, not residences.

One honest detail about how RepTrack tallies zone time: each stretch of a workout is credited to the zone of the measured sample that opens it. No interpolated crossings, no invented "you must have passed through zone 4" seconds, measured time only.

And a design note worth knowing: in RepTrack, zones are a reporting layer. Your Strain score integrates the raw heart-rate signal directly; the zone table is a readable summary of the same workout, not an input to the math. The colors can't bend your score.

Why "220 minus age" fails you

The formula everyone knows was never derived as a precise individual predictor, and its error bars are enormous: real HRmax at any given age spans a range of ±10–20 beats around any formula's line. A 40-year-old's "predicted" 180 could truly be 165 or 195. Cut zones from a number that's 15 beats wrong and your "easy" runs are threshold work, or your "threshold" work is a stroll.

The research consensus is that Tanaka's formula (208 − 0.7 × age) fits populations better than 220 − age, especially past 40, where the old formula under-predicts. But even Tanaka is a population line, the honest hierarchy is: a real measurement beats any formula.

RepTrack's HRmax ladder

RepTrack resolves your HRmax through a ladder, best evidence first, and tells you which rung you're on:

1. Your manual value wins outright. If you've done a proper max test (or have lab data), enter it and every formula steps aside.
2. Otherwise: the larger of observed vs. Tanaka. RepTrack scans your last 12 months of recorded workouts for the highest heart rate you've actually hit, and compares it against the Tanaka estimate from your age. The larger one wins, because if your watch has seen you at 194, a formula claiming 183 is simply wrong, and a max heart rate is by definition a number you reach, not an average.
3. No age on file, nothing observed? A clearly-labeled assumed 190 with a prompt to complete your profile. It's used instead of refusing to work at all, but it carries a visible confidence penalty until a better rung takes over.

Everything is clamped to a physiological 120–220 range so a sensor glitch or a typo can never become your training ceiling. The observed value refreshes weekly, a 12-month percentile doesn't move fast enough to justify rescanning a year of data every morning.

How to actually train with zones

• Most of your cardio belongs low. The bulk of endurance volume in well-studied training distributions sits in the easy bands (zones 1–2 in three-zone language, roughly your 60–70% band here), with hard work concentrated and deliberate, not a daily grey-zone grind.
• Use zones to keep easy days easy. The most common self-coaching error isn't going too hard on hard days; it's creeping to 75% on recovery days. The zone readout is your accountability.
• Anchor hard intervals to Peak, not Max. 80–90% is repeatable training stimulus. 90%+ is for finishes and tests; if every interval ends there, they're too long or too few.
• Check the rung, then trust the zones. If your HRmax is on the assumed-190 rung, fill in your age, one profile field re-cuts every zone. If you're on Tanaka and your hard efforts keep tapping the ceiling, your real max is probably higher: the observed rung will catch it, or a field test will.
• Zones describe cardio, not lifting. Heart rate under a barbell reflects load and rest periods more than aerobic intensity, that's exactly why RepTrack's Strain has a separate muscular channel.

The bottom line

Zones are just percentages of one number, so RepTrack spends its effort getting that number right: your tested max if you have one, otherwise the larger of what your watch has actually seen in a year and the best-fitting formula, never silently, the source is always disclosed, and a placeholder is always labeled. Cut from a real max, the five bands become what they should be: a way to keep easy days honest and hard days deliberate.

Sources

• Tanaka H, Monahan KD, Seals DR. "Age-predicted maximal heart rate revisited." Journal of the American College of Cardiology, 2001, 208 − 0.7 × age and the failure modes of 220 − age.
• Robergs RA, Landwehr R. "The surprising history of the 'HRmax = 220 − age' equation." Journal of Exercise Physiology, 2002, the formula's origins and error bars.
• Nes BM, et al. "Age-predicted maximal heart rate in healthy subjects: The HUNT Fitness Study." Scandinavian Journal of Medicine & Science in Sports, 2013, population HRmax spread at every age.
• Seiler S. "What is best practice for training intensity and duration distribution in endurance athletes?" International Journal of Sports Physiology and Performance, 2010, polarized/pyramidal intensity distribution.
• Karvonen MJ, et al. "The effects of training on heart rate." Annales Medicinae Experimentalis et Biologiae Fenniae, 1957, heart-rate reserve as a training-intensity anchor.