Zone 2 Or Not To Zone 2? That Is The Question

In part one of my series on training data, I discussed the 5-zone model of analyzing heart rate data. Today, I’d like to focus on one of those zones in particular: the infamous zone 2. 

The most ubiquitous argument in the running-related corners of the internet is whether you should “run slow to run fast” or “run fast to run fast.” The first camp argues that volume is the biggest factor in improving as a runner, and that running easier on your easy days allows you to stack more miles without risking injury or overtraining. The latter camp argues that running fast requires event-specific training; the best way to run a fast mile is to get your body used to running at your mile pace before the race.

Like so many evergreen internet arguments, the answer here is that both sides are partially correct.

First, let’s talk about the value of running in zone 2.* Since consistency over time is the backbone of solid training and the best way to improve in the long term, zone 2 represents a sweet spot where you get good bang for your buck: you can run quite a lot of miles in zone 2 with lower injury risk relative to higher intensities. You’re also less likely to experience mental burnout if your go-to pace is relatively easy: running is simply more fun if you know you’re not going to absolutely gas yourself every time you step out the door.

However, there are some approaches that I think emphasize zone 2 running too much—in particular, the popular Maffetone Method (MAF for short). According to the MAF method, you should subtract your age from 180 to find your absolute maximum heart rate for your running for 3–6 months, with modifications made for injuries and such. For me, that would mean running at a maximum of 148 bpm. While that’s a totally fine and reasonable effort for me to be at for easy runs—and in fact, I take most of my easy days easier than this—I would be losing out on a ton of fitness gains if I never trained at higher effort. There are specific physiological adaptations that you only get by running hard, not to mention the mental toughness benefits of completing a hard workout.

Steve Magness has argued that “there are no magic training intensities” that will give you outsize benefits. Some running plans feature a huge emphasis on, say, threshold pace, easy running, or VO2 max pace, but the truth is that all these efforts are related and each one supports all the others. They all need regular attention.

Last year, ultra runner and coach David Roche set the men’s course record in the Leadville 100 miler, finishing in 15 hours 26 minutes. Even considering the elevation and vertical gain, his average pace of ~9:30/mi isn’t eye-poppingly fast. But Roche has been open about the fact that he emphasized speed in his preparation: he said that he wanted to be able to capable of running a mile in the low 4 minute range and capable of running a sub-15:00 5K at altitude—around a 4:50/mi average pace. He’s also claimed that the winner of this year’s Western States 100 will be the runner who shows up on the start line capable of running the fastest all-out mile. Essentially, his theory is that being well rounded is the key to success regardless of your race distance.

There’s no silver bullet. A solid training plan is periodized and incorporates a variety of paces on a regular basis, becoming more specific to the requirements of the peak race as it progresses. So yes: to get faster, you should run slow, and fast, and everything in between.

*There are folks who like zone 2 for its supposedly unique fat-burning benefits, but I’m not a dietician and my primary goal isn’t to help folks lose weight or burn fat, so I’m not going to get into that one way or another.