10km = 16km (6.25mi = 10mi)

Have you heard the saying that your brain can’t tell the difference between reality and imagination?

Well, the same is true with your body and running.

After a run, your body doesn’t care about how many miles/kilometers you ran; it cares about how much stress it felt. And it’s super important to understand it to improve your training and reduce your chances of getting injured.

Let me explain by comparing the following two workouts.

First, an easy long.

I did this 16km run three weeks before my sub-5-minute mile and 16-minute 5k races last year.

It was scheduled as a zone 2 run, and I dialed my heart rate perfectly, 143 bpm on average. I remember feeling strong and happy with that run.

Second, my first long run of the year.

I did this 10km run after the Christmas holiday (where I gained 10 pounds), I started a new training program, and it was freezing cold, 14°F (-10°C). So I had to wear two jackets, two pairs of gloves, tights, and thick merino wool socks.

It was scheduled as a zone 2 run, but when I finished, I felt abnormally tired. And when I analyzed the data, I found out that I ran it at an average of 158 bpm, zone 3. It was a struggle to keep my heart rate under control with all the layers and icy conditions.

No wonder I felt terrible. It wasn’t an easy run; it was a 10km tempo run at the beginning of my training cycle when my body was not ready yet.

And the very interesting thing here, and the point of this article, is that if you compare the stress my body suffered from each one of the workouts, using the CSI score (more on that below), they are practically the same:

  • 68 for the 16km workout
  • 67 for the 10km workout

How’s that possible?

Your body doesn’t understand distance; it doesn’t care if you run 10 or 16km.

It only cares about how long and how hard you ran, how much stress it experienced during a run, just like when your brain can’t tell the difference between reality or imagination.

But, if my body experienced the same stress with both workouts, why did I feel great on one and terrible on the other?

The answer is very simple.

One workout was at the end of a training program, and the second one was at the beginning.

After more than three months of training consistently and improving my fitness, my body was ready for that easy 16km run.

But at the beginning of my training, after Christmas and overweight, a 10km tempo run was too much.

And that precisely is why we developed the CSI score inside Bannister.

First, to create a training program that stresses your body the right amount each week to help you improve as a runner.

It then reads the data from each of your workouts, compares it with the expected one, and adjusts and adapts your training program accordingly.

This way, you not only have a 100% personalized training program, but you also have a training program that evolves with you.

A program that considers the real stress your body is experiencing and adjusts it to keep you improving and reducing your chances of injury.


If you want to learn more about how Bannister creates a 100% personalized training program so you can maximize your time and workouts to achieve your goals faster, click the button below.

And if you have any questions, you can write to diego@bannister.coach.

Diego Alcubierre, a passionate runner and coach, started his journey at 26 with a 10k time of 1:06:23 and has since slashed 30 minutes off his personal record. With five running and coaching certifications, Diego is committed to sharing his expertise and proven strategies to help runners of all levels enhance their performance, stay motivated, and enjoy the journey of running. At Bannister, he simplifies complex training concepts, empowering you to achieve your running goals.