Why zones exist at all
Heart rate by itself is a number without context: 150 bpm is a jog for one member and a maximal effort for another. Zones fix this by expressing effort as a percentage of each person's own maximum, which makes intensity personal, comparable and coachable. When a class trains "in zone 3", everyone is doing the same relative work at different absolute heart rates. That single idea is what makes group heart rate training possible, as we show in group heart rate training for gyms.
The five zones, and what each one is for
Zone 1, roughly 50 to 60% of max: recovery. Warm-ups, cool-downs, easy movement on rest days. Its job is circulation and habit, not adaptation.
Zone 2, roughly 60 to 70%: the aerobic base. Conversational effort that builds the engine: mitochondria, capillaries, fat metabolism. Chronically underrated by members because it feels too easy; we dedicated a full piece to coaching it in zone 2 training.
Zone 3, roughly 70 to 80%: steady endurance. Comfortably hard, sentences become phrases. Where most untrained members drift by default, which is exactly why coaches need the screen: zone 3 is fine on purpose and mediocre by accident.
Zone 4, roughly 80 to 90%: threshold. Hard, sustainable in blocks of minutes, trains the ability to hold speed. The productive discomfort most intervals aim for.
Zone 5, 90% and above: maximal. Seconds to a couple of minutes, full commitment. Powerful in small doses, corrosive as a habit; if every session visits zone 5, none of them trains it properly. Interval structure for zones 4 and 5 is covered in HIIT heart rate zones.
Boundaries vary by model and vendor by a few points; the training logic does not. What matters is consistency within your club, so members learn one language.
The honest problem: estimating maximum heart rate
Every zone is a percentage of a number most members have never measured. The classic 220 minus age formula is a population average with a wide individual spread: real maxima commonly sit well above or below it, which means formula-based zones can be wrong for a given member. Alternatives like the Tanaka formula, 208 minus 0.7 times age, shift the average but not the spread.
Practical approach for a club: start from a formula, then correct with evidence. A submaximal field test under coach supervision, or simply weeks of real data, a member repeatedly touching "96% of max" without distress has an underestimated max, converge on zones that match the person. Systems that track effort over time make this recalibration natural rather than a spreadsheet job. And the correlated resting numbers tell their own story, covered in resting heart rate by age and heart rate recovery.
Using zones in a real class
Coach the colour, not the number. "Get to orange and hold it" works across a mixed room; "go to 152" works for nobody. Live zones on the screen make the instruction visible and self-correcting.
Design sessions as zone journeys. A written plan, warm to blue, three blocks of orange with green recoveries, one red finisher, turns a playlist workout into programming members can feel and repeat.
Use zones to protect beginners. The screen tells a coach instantly when the deconditioned newcomer is redlining during the "easy" section. That intervention, made early and kindly, is a retention moment: nothing loses a new member faster than a first week that felt dangerous.
Let zones accumulate into points. Time in zone converts naturally into effort scoring, Uptivo Performance Points work exactly this way, which is what connects a single session to streaks, challenges and the retention loop described in heart rate based retention.
The takeaway for operators
Zones are simple enough to teach in one class and rich enough to structure years of programming. The prerequisite is making them visible: on the wall during class, in the app afterwards, on whatever device the member already wears. If you want to see a mixed room training in the same zones on twenty different devices, speak to an expert.