Heart rate zones, Effort and Strain
The Intensity section of a workout answers a question raw duration cannot: how hard was that, really? It splits your session across five heart rate zones and summarises the result as two scores.
How the zones are calculated
Stepzy estimates your maximum heart rate with the standard age formula - 220 minus your age - reading your date of birth from Apple Health. The five zones are then percentages of that maximum.
| Zone | Percent of max HR | Typical feel |
|---|---|---|
| Zone 1 | Below 50% | Very light - warm-up, recovery |
| Zone 2 | 50-60% | Light - conversational walking |
| Zone 3 | 60-70% | Moderate - brisk, steady effort |
| Zone 4 | 70-85% | Hard - you cannot hold a conversation |
| Zone 5 | Above 85% | Maximum - short bursts only |
The HEART RATE ZONES card shows how long you spent in each zone and what share of the workout that was. If your date of birth is missing from Health, Stepzy falls back to a default age - add it via Body Measurements in Settings for accurate thresholds.
The 220-minus-age formula is a population average and can be out by ten beats or more for an individual. Treat zone boundaries as a guide, not a hard line. You can run the same maths on the web with the heart rate zone calculator.
Effort
A score out of 100 derived from your time in each zone - it answers how intense the session was. Stepzy labels it Light, Moderate, Vigorous, Intense or Maximum.
Strain
Also out of 100, but it reads as training load - how much the session asked of your body overall - rather than peak intensity. Its labels are Light, Moderate, High and Very high.
The Effort and Strain cards require Stepzy Pro. The zone breakdown, heart rate graph and the min, average, max, HRV, VO2 max and breathing tiles are available to everyone.
The heart rate graph
Below the tiles, a graph plots heart rate across the session with max, average and minimum called out. Drag along it for a BPM reading at any point - handy for spotting the hill you underestimated.
Frequently asked questions
Why are my zones empty?
The workout has no heart rate samples in Apple Health. Heart rate needs an Apple Watch or a paired chest strap - an iPhone alone cannot record it.
Which zone should I train in?
For general health and walking, most of your time sits comfortably in zones 2 and 3. Stepzy is a wellness app, not a coaching service - speak to a professional for structured training advice.
How do I fix wrong zone boundaries?
Add or correct your date of birth. Open Settings, tap Body Measurements, set Date of Birth, then reopen the workout.
Stepzy is free on the App Store, for iPhone and Apple Watch.