Running: It's the duration, not the distance

Your body will tell you that running 50km over a mountain trail is harder and stresses it more than running 50km over a flat course.
Your body will tell you that running 50km over a mountain trail is harder and stresses it more than running 50km over a flat course.PHOTO: SALOMON

Your body senses the time you spend, not kilometres logged

In a world of constant technological advancements, more metrics than ever before are available for runners to dissect their performance. Time, pace, heart rate, cadence and elevation. Power, vertical oscillation, VO2max estimate and stride length. The list goes on.

While each of these can be useful, there is one metric that gets discussed and debated more than any other - distance, also known as mileage. This refers to kilometres or miles run in a session, week, month, year or lifetime.

It is an essential metric and, as the old saying goes: Miles make champions.

Because of this, many runners have an obsession with mileage targets. They structure their training using distance and believe you must run a certain percentage of your race distance during your long run.

In my opinion, runners place far too much weight on the importance of distance. Your body has no comprehension of what a kilometre is; it knows only how hard it is working and how long it is working. That is effort over time.

As you will see in the training plan I have written for The Straits Times Run on Sept 29, I always prescribe mileage in the form of duration, not distance.

The time you spend is more important than kilometres logged because it is the duration of effort your body senses.

Rather than think "I need to run 10km", think "I am going to run for 70 minutes".

A fast runner will cover more distance in the same time than a slower one. For example, the runner who averages 41/2 minutes/km for 60km a week, is on his feet the same amount of time as the 9min/km, 30km runner and therefore, experiences the same amount of stress.

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And that is what matters - the stress.

If slower runners try to go as far as someone faster, it would involve more stress and puts themselves at a higher risk of injury.

It is also important to note that not all mileage is equal, and several things change the difficulty of running a certain distance.

 • Terrain: 50km over mountain trails is harder and stresses the body more than 50km over a flat course.

 • Climate: 50km in a tropical climate, like the one we battle in Singapore every day, is harder than 50km in New Zealand's more temperate weather.

 • Altitude: 50km at altitude is harder than 50km at sea level because there is less available oxygen to fuel the working muscles, so the body has to work harder.

 • Intensity: A 50km hard run stresses the body significantly more than the same 50km run easy.

 • Frequency: 50km over two runs loads the body differently to 50km over five runs and can change the training effect.

Running for time helps to self-correct for the terrain, weather, altitude and your level of fatigue. You will run less distance in the same time when the external stress is high and that is fine. The converse is also true.

Rather than worrying about distance, move your focus to time spent. I believe you want to run as much as you can comfortably recover from, without losing motivation, getting sick or injured.

In my experience, that will fluctuate week on week with the stress of life, and that is okay.

A version of this article appeared in the print edition of The Sunday Times on June 30, 2019, with the headline 'It's the duration, not the distance'. Print Edition | Subscribe