Michael Reibel Boesen

July 11, 2022

🏃‍♂️80/20 running: The beginning


Currently about 80% done with Matt Fitzgeralds book “Run like a pro (even if you’re slow)” and it’s really convincing. It advocates a lot of (to some extent) counter intuitive practices that the pros are using and that recreational runners should use too but very often fail to do.

One of the most interesting and counterintuitive of these is Matt’s “80/20 running” (he wrote a whole book about that which is definitely next on my list). Which basically says that 80% of the time running should be spent at low intensity and the remainder 20% should be spent on moderate or high intensity depending on which kind of goal I have.

In all runs I’ve done up until this point I’ve just been more or less trying to full throttle (air quotes) my way through. Air quotes because that’s still not very fast, but it’s for sure high intensity for me. When asked by my current running app of choice Nike Running Club (it’s just so damn beautiful) about the intensity I would always reply somewhere between 7 and 9. So suddenly having to use the brakes a lot during a run feels weird 🙃 But the data is there so I decided to give it a try after recently started to run again after 1.5months break.

But what does low intensity mean? According to Matt, low intensity is runs that are run at 80% of max heart rate or 65% of VO2Max (the exertion at which your body is absorbing the highest amount of oxygen it can possibly do at your current fitness level). At 65% of VO2max is your VT1 (Ventilatory Threshold #1) and if you cross that one you will see a spike in breathing rate and heart rate (if I remember correctly).

He then gives a number of ways to calculate that. I tried one of them the so called 6 minute test which calculates the pace I should keep to stay below VT1. To do the test I had to run at a pace that I could sustain for 6 minutes straight. Looking at some of my former runs I could see that the fastest 1K I did was 5:30min/km, so I was reasoning that the fastest I could go for 6 minutes is probably around 5:00 min/km. So that was my target. I set the watch for 6 minutes and boom off I went 🏃‍♂️💨. Checking the watch all the while it said 5:20 or something. Damn I need to go faster! A minute or so later I checked it again and now it said 4:00min/km - arg too fast. And sure enough at about 1min left I completely tanked. Acid everywhere and I were almost coming to a complete standstill. Ending up with an average pace over the 6 minutes of 5:18min/km (and beating my fastest 1K though) and I was going well below 6:00min/km at the very end and I probably looked like I was about to die.

So yeah not the perfect stable 6 minute run I had envisioned. But now I know that my Apple Watch with the Nike Running Club app is apparently lagging by quite a bit. I’m going to redo the test in a few days but for now I’m sticking with the 5:18min/km.

So my pace at VO2Max (pVO2Max) is 5:18min/km. Converting that to velocity at vVO2Max = 11.3 km/h. Taking 65% of that will give me my velocity at VT1 (vVT1) which is then 7.36 km/h and converting to pace and I get pVT1: 8:09min/km. So this the pVT1 I’m going with for now.

So how is it working? 

To early to tell. I’ve done 2 interval runs at that pace [1min walk / 3min low intensity run] and [1min walk / 4min low intensity run] and both of these ended up in a pace just around 8min on average - but this includes walks. Here are some things I noticed:
  • 🏃‍♂️Pace: Feels glacial (pre-climate-change). I can’t for the life of me get my running pace down to 8:09min/km. The slowest I seem to be able to move my legs and still run is 7:30ish min/km. The pace feels really slow.
  • 🌊Sweat: In this last one I just finished a few minutes ago, I was running in the sun probably around 25C in direct sun and I only started sweating after 20 mins. Really unusual for a guy that haven’t really worn a shirt all weekend because of the heat.
  • ❤️Heart rate: If I’m looking at my heart rate data, for instance on this last one I just completed it seems to stay around 150 about midway through when I’m running and if you just do the very simple max HR calculation for someone my age my 80% heart rate should be right around there.  
  • 🌬Breathing: It hardly feels like I’m breathing. Maybe a bit deeper breaths than when I’m just sitting and writing this post. 
  • 💪Endurance: Finally, I feel like I could keep that pace up for hours. 

So yeah, based on these observations it might look like I’m hitting that VT1 spot pretty good based on that.

For reference here are the two 80/20 runs including the 6minute test on Strava:
6 minute vVO2max test
Run #1
Run #2
It should be noted that inbetween run #1 and #2 I did a moderate effort 5K not shown here where I tried to keep a bit above my VT1 and I was surprised to see that I could actually run for 27 minutes with no problems at that pace.

This is part 1 of my adventures with 80/20 running. Stay tuned for more posts on that in the future.

About Michael Reibel Boesen

Dad 👨‍👩‍👦‍👦, builder (🤖⌨️🏢), 💌 Weekly Climate, 🚁📸photographer, 🎧vinyl record collector and reseller, 🥃 distiller (Gefjun), 🎸guitarist, 🎹pianist, 🍷winenerd (WSET3), 🏃‍♂️runner and 🤓engineer/PhD.