Why the "easy long run" is so important

Did you know that optimal running training consists mostly of easy base runs?

These are runs at an intensity that challenges us slightly but definitely does not overburden us. In training plans, this session is listed as Zone 3.

Definition of an easy long run

The intensity corresponds to about 70% to 80% of the maximum heart rate. Anything above 80% is no longer considered an easy long run. And importantly: A "too low" intensity is not an easy long run either, at least it no longer has the effect of an easy long run. This means that the often mistaken advice to run as slowly as possible to get faster is absolute nonsense. Running training only becomes beneficial for performance progress at around 65% (or rather 70%) of maximum heart rate. Anything below that is restorative training and has no impact on improving performance.

The pace is crucial!

But why is the Zone 3 run so important? The pace is roughly 45 - 90 seconds slower than your 10-kilometer race pace. For example, if you have a personal best of 40 minutes for 10 kilometers (= 4 min/km), your base pace should be in the range of 4:45 min/km to 5:30 min/km. Make sure to stay within this range. Your heart rate should be around 70 - 75 / 80% of the maximum heart rate.

Why we benefit so much from the Zone 3 run!

But why are these easy base runs in the relaxed to slightly demanding range so important for us runners? The American personal trainer and exercise physiologist Armen Ghazarians summarized it very well on the athlete portal SweatElite: Through regular aerobic easy runs, our body learns to use fat reserves more efficiently. Ghazarians refers to this as the "fat adaptation effect". During intense sessions such as tempo runs, intervals, and races, our body resorts to quickly available carbohydrates. Without incorporating slower runs, the body would struggle to access fat reserves as an energy source, since it wasn't trained to do so. However, during aerobic runs, our body uses 50 percent of energy from fat and the other 50 percent from a combination of glucose and proteins.

A decisive advantage for marathon runners

In the long term, energy generation from fat has great benefits: Through regular aerobic runs, the body learns to use fat as the main energy source instead of carbohydrates. This allows for running longer distances before energy stores are depleted. This has a major advantage, especially for marathon runners.

More benefits of easy long runs

But there are more reasons to support easy base runs: Our heart, lungs, and muscle system are trained to work more efficiently. During longer runs, we can maintain a faster pace with less effort. Additionally, our Type I muscle fibers are trained, which are responsible for maintaining a steady pace in the aerobic range for as long as possible. This means our endurance improves as well.

Ghazarians also claims that the risk of injury is reduced during aerobic runs. Tendons, ligaments, joints, and bones can better adapt to stress during running through base runs. This leads to a lower injury risk.

How often should we run easy?

But how high should the proportion of easy long runs be in our training volume? The proportion should range from 66% to 80%. The 80:20 rule is often mentioned, where 20% of the weekly mileage should be at an intensity above 80% of the maximum heart rate, and the remaining 80% should be in the range of 60 - 80% of the maximum heart rate. With this approach, you are definitely on the safe and "right" side as a runner.