July 9, 2019
The Mileage Metric
The amount of time you spend running is more important than the number of kilometres you log because it’s the duration of effort that your body senses.
This post was originally written for The Straits Times as part of a 16-week column preparing runners for The Straits Times Run 2019.
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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’s one metric that gets discussed and debated more than any other. Interestingly, it’s one of the oldest.
Distance, a.k.a mileage.
Mileage refers to the number of kilometres or miles you run in a session, week, month, year or lifetime.
It’s 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.
Cut Race Times, Not Corners.
Racing at your potential and enjoying training is easy when you’re following the right programme.
Run For Time, Not Distance
In my opinion, runners are placing far too much weight on the importance of distance run. Your body has no comprehension of what a kilometre is; it only knows how hard it’s working and how long it’s working. That’s effort over time.
As you’ll see in the training plan I wrote, I always prescribe mileage in the form of duration, not distance. The amount of time you spend running is more important than the number of kilometres you log because it’s the duration of effort that your body senses.
A fast runner will cover more distance in the same amount of time as a slower runner. For example, the runner who averages 4:30-minutes per kilometre for 60 kilometres per week is running the same amount of time as the runner who is running 9-minutes per kilometre for 30 kilometres a week and is, therefore, experiencing the same amount of stress.
And that’s what matters – the stress.
If a slower runner tries to run as much distance as someone faster than them, the slower runner will experience more stress and therefore puts themselves at a higher risk of injury.
It’s also important to note that not all mileage is equal, and several things change the difficulty of running a certain distance.
Terrain. 50km a week run over mountain trails is harder and stresses the body more than 50km run over a flat course.
Climate. 50km run 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. At altitude, there is less available to oxygen to fuel the working muscles. As such, the body has to work harder. 50km at altitude is harder than 50km at sea level.
Intensity. 50km a week run hard stresses the body significantly more than the same 50km run easy.
Frequency. 50km a week run over two runs loads the body differently to 50km run 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’ll run less distance in the same time when the external stress is high – and that’s fine, the converse is also true.
Rather than worrying about the distance you’re running, I encourage you to move your focus to time spent running. I believe that 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’s ok.
Ben Pulham