Photo: bgstock72 via Canva.com

Endurance training is fundamentally simple, but not always easy to put into practice. About 75–80% of your sessions should be performed at low intensity, while only 20–25% should be dedicated to high-intensity training.

This principle is now widely known. However, in practice, it often proves difficult to implement. Interestingly, the main challenge is not so much the high-intensity sessions, but managing the large portion of training, the 75–80%, that should be done at low intensity.

A closer look at the training logs of amateur athletes shows that, although they rarely train at very high intensities, they also rarely train often enough or slowly enough to properly optimize their fat metabolism. Many operate constantly within a mid-intensity zone, often referred to in training theory as the "forbidden zone."

The problem is clear: if most of the training volume is completed at too high an intensity, the essential aerobic base is missing. The body quickly switches to burning carbohydrates instead of fats. Even if the high-intensity sessions are perfectly executed, without a solid fat-burning foundation, performance will inevitably decline, especially during competitions lasting over an hour.

The solution seems simple

It becomes clear that, if such a large portion of training is meant to be done at low intensity (<75 % of the maximum HR), athletes must recognize its importance and focus on executing these sessions properly.

For most athletes, this means two things: first, increasing the proportion of endurance sessions carried out at low intensity to about 75–80% of the total; second, strictly maintaining low intensity during these sessions (endurance run, long jog). Anyone who tries to maintain pace uphill or draft behind others when overtaken ends up working at a higher intensity, disrupting metabolic processes. It can then take up to half an hour before the body returns to its original metabolic target. You are in the correct intensity range if your heart rate is no more than 75% of your maximum heart rate and you can maintain yourself in full sets.

Conclusion

Not only you, but even the best athletes must learn to run or ride slowly. At first, it may feel unusual or less satisfying compared to the more dynamic pace you are used to. However, take your time and try to better differentiate your efforts: go slow when you are supposed to go slow, and go fast when it is time to go fast.