Understanding Heart Rate Zones During Exercise
Heart rate is the most direct real-time indicator of exercise intensity. Maximum heart rate (MHR) is estimated using the formula 220 − age, and training zones are defined as percentages of this value. Each zone activates different energy systems and produces different physiological adaptations. Staying in the right zone for your goal is key to safe and effective training.
The fat-burning zone (60–70% MHR) uses fat as the primary fuel source, while the cardio zone (70–80% MHR) is most effective for improving heart and lung capacity. Above 90% MHR is only appropriate for brief high-intensity intervals, and should be avoided by beginners and anyone with cardiovascular conditions. Using a heart rate monitor during exercise is the most reliable way to stay in your target zone.
Frequently Asked Questions
A smartwatch or chest strap heart rate monitor gives the most accurate readings. Without a device, find your pulse at your neck or wrist, count beats for 10 seconds, and multiply by 6 to get your bpm.
This is a population average with a standard deviation of ±10–20 bpm. For general training guidance it is sufficient, but for clinical purposes, a maximal exercise test under medical supervision provides an accurate individual measurement.