High-Intensity Exercise (Z4-Z5)

In PeakWatch, "Z4-Z5 Training Time" records the time you spend in the high heart rate zone. This usually corresponds to "vigorous intensity" physical activity in sports science and is key to improving athletic performance and cardiorespiratory limits.

What is Z4-Z5 Intensity?

When you enter this zone, your body is going all out. You will feel short of breath and almost unable to speak a complete sentence. Your heart rate is above 80% of your maximum heart rate. This intensity of activity is common in interval sprints, hill running, or high-intensity cruising.

Why Challenge High Intensity?

Although Z1-Z3 is the cornerstone of health, the stimulation of Z4-Z5 can bring you deeper physiological benefits:

  • Improve VO2 Max: High-intensity exercise forces the heart and lungs to work at maximum efficiency, significantly raising your cardiorespiratory endurance ceiling.
  • Stronger Afterburn Effect: Training at this intensity not only burns calories during exercise but also keeps your metabolic level high for hours after class because the body needs more energy to repair and recover (EPOC).
  • Lactate Tolerance: High-intensity training gets your muscles used to working in a sore state, improving your ability to maintain high speeds.

Evaluation Standards in PeakWatch

Since high-intensity exercise is more stimulating to the body, we recommend doing it after a full warm-up and have set the following weekly reference goals:

  • Low: Less than 15 minutes per week. If your aerobic foundation is already solid, it is recommended to add an appropriate amount of intensity training to break through physical bottlenecks.
  • Good: 15 to 75 minutes per week. This is the high-intensity exercise range recommended by the World Health Organization (WHO), sufficient to maintain excellent cardiovascular efficiency.
  • Excellent: 75 to 150 minutes per week. This means you have extremely strong physical fitness and recovery ability.

Training Suggestions

High intensity does not mean going to "failure" every day. It is recommended to distribute these durations evenly among 1-2 key training sessions per week. PeakWatch will monitor in real-time whether your heart rate enters Z4 or Z5 and help you accurately record these moments of challenging limits.

Focus on Recovery

After high-intensity training, the body needs longer to repair tiny muscle damages. If you find your high-intensity duration is too high in PeakWatch, it is recommended to increase Z1-Z3 recovery activities in the following days to ensure the body can digest these loads.