In athletic training, heart rate isn't just a medical indicator; it reflects exertion and recovery capacity. Understanding heart rate zones allows runners to tailor training programs for half marathons, full marathons, or performance improvement.

According to Doctor Dinh Huynh Linh from the Cardiology Institute at Bach Mai Hospital, heart rate is a relatively objective indicator of exertion. Training within specific heart rate zones optimizes workouts. Low heart rate exercises improve aerobic metabolism and endurance, while high heart rate exercises enhance oxygen utilization, helping runners maintain speed during competitions.

Doctor and runner Dinh Linh uses a watch during training. Photo: FBNV/Dinh Linh

Doctor and runner Dinh Linh uses a watch during training. Photo: FBNV/Dinh Linh

Garmin divides heart rate into five main zones based on maximum heart rate (Max HR): Zone 1 (50-60%) is suitable for warm-ups, recovery, and stress reduction. Zone 2 (60-70%) enhances endurance and fat burning, comprising most training time. Zone 3 (70-80%) improves lactate threshold for steady runs. Zone 4 (80-90%) focuses on speed and endurance, often used for interval training. Zone 5 (90-100%) improves VO2max but is used briefly under strict control.

Following the 80/20 principle in endurance sports, runners should spend about 80% of their training time in low heart rate zones (Zones 1-2) to build fitness, increase endurance, and reduce injury risk. The remaining 20% is for higher-intensity exercises (Zones 3-5) to improve performance and speed. For example, if running five hours per week, four hours should be easy running and one hour at high intensity.

Incorrectly applying this principle, such as maintaining medium to high intensity for most of the training, can lead to overload, fatigue, injuries, or ineffective results. Accurate heart rate monitoring is key for effective and sustainable training.

Devices like sports watches are important for monitoring and personalizing maximum heart rate, optimizing training zones for each user. This is particularly helpful for runners aiming for long-term goals like half or full marathons.

Some newer sports watches, such as the Garmin Forerunner 570/970, are equipped with the Gen 5 Elevate heart rate sensor, a new optical technology that allows continuous heart rate monitoring with high accuracy during both training and daily activities.

Users can also set heart rate alarms for notifications when exceeding safe thresholds and track HRV (heart rate variability) to assess stress levels and post-workout recovery. Some high-end models offer ECG (electrocardiogram) functionality for regular heart health checks, enabling training and rest plans tailored to actual physical condition. These tools help runners train intelligently, enhancing endurance sustainably and effectively.

Garmin watches help track heart rate. Photo: Wareable

Garmin watches help track heart rate. Photo: Wareable

Runner Nguyen Van Hung (TP HCM) shared that he used to experience shortness of breath and muscle pain while training for a half marathon due to constantly maintaining a high pace in zones 4-5. After four weeks of adjusting his training based on heart rate zones using a sports watch, he saw significant improvements in performance and reduced fatigue.

"I used to think that training harder would improve performance faster, but only by listening to my heart through the data did I learn my limits and how to adjust," he said.

Listening to one's heart is a way to understand the body's limits, plan training appropriately, avoid injuries, and maintain long-term progress in running.

Lan Anh (according to Runner World, Garmin)