Welcome to Earth

What is Zone 2 Training?

WELCOME TO EARTH: Fartlek Training

Welcome to Welcome to Earth, the POSSESSED department where an alien asks a running-related question and we try to answer it. 

This month’s letter comes from Umm who hails from Huh?, one of the 20 billion earth-like planets in the Milky Way (didn’t make that up). Umm writes:


My name is Umm and I live on the planet Huh? Huh? is virtually identical to your planet Earth, the only real difference being Huh? doesn’t have reggae, chlamydia, or whatever this Zone 2 thing is. So, what is it? What is Zone 2 training?

Lots of love,


Wow, Umm, Huh? sounds fantastic, and what an excellent question, too. Zone 2 training—what is it? Let’s find out.

When it comes to physical activity, the human heart has five distinct zones. The first zone, Zone 1, is the chillest, and Zone 5 (the fifth zone) is the maximum heart rate zone. There is a sixth zone, but no one has been there and lived to tell the tale. According to sports science, of all the five zones, Zone 2 is the ideal area for base training. It’s a medium effort zone (60 to 70% of your maximum heart rate), which means it can be maintained for a long time. The easiest way to find Zone 2 during a run is to run with a friend and have a chat. If you find talking difficult or impossible, you have officially left Zone 2. If you’re running at a pace that allows you to converse with your friend, you’re in the correct Zone. If you’re running without a friend to talk to, try singing Billy Joel’s ‘We Didn’t Start the Fire’. If you have an asthma attack before you get to Buddy Holly, Ben-Hur, Space Monkey, Mafia, you’re out of the zone and running too fast. Slow down, hot-rod. Get into Zone 2 and stay there.

Another thing you should know, Umm, is that Zone 2 generally makes up around 60% to 70% of a human endurance athlete’s training schedule. They may slip into Zone 3 here and there, but overall, they’ll stay in Zone 2 because that’s where their aerobic base is built. They go slower to help them go fast. You’d think running quicker and pushing yourself would improve performance, but it doesn’t. At least not as well as Zone 2 does. Medium effort Zone 2 workouts are the best way to train a human body to use oxygen with optimal efficiency, which will result in improved athletic performance. But the benefits don’t stop there...

Zone 2 training is also the best way to avoid injury. Tempo runs are fun, but if that’s all you’re doing, you run a higher risk of busting something. Throwing in a few low-intensity Zone 2 runs each week will allow your body to recover from the crazy fast shit, and because Zone 2 training actually enhances blood flow, your muscles will repair faster and your joints will be much happier. Furthermore, Zone 2 running is excellent for your Cardiovascular fitness. Your heart benefits from sustained medium effort even more than it does when you’re doing nothing. Surely, a resting heartbeat is better for you, right? Nope. Zone 2 pushes blood through the body and sweeps away the cobwebs lurking in the veins.

One final advantage of Zone 2 training is that it’s excellent for your mental health. As a rule, running in any zone is terrific for your head, but most of the benefits are in longevity: the longer you run, the better you feel. And obviously, you can run longer when you’re not going too fast. And you’re more likely to experience the elusive ‘runners high’ after a long Zone 2 run than in a shorter tempo run. I’m speaking from personal experience, but anecdotally, that seems to be the deal.

There you go, Umm, we hope that clears up Zone 2 Training for you!

If you’re an alien (or someone who thinks they're an alien), and you have questions about earthlings and running, write to us here!