Max HR = 220 − age; training zones expressed as percentages of max HR
Age 35: Max HR = 185 bpm; moderate zone (50–70%) = 93–130 bpm.
It's a widely used estimate but can vary ±10-15 bpm per individual; a lab test gives a more precise max HR.
Typically the 60–70% zone, though total calories burned matters more than the specific zone.