Sweat Science 101 Email Series

The following is the first installment of Alex Hutchinson’s Sweat Science 101 newsletter series, a ten-part crash course on how to train, fuel, and recover. Sign up today.

I’ve been writing the endurance-focused Sweat Science column, in various incarnations, for 17 years now. That means I’ve gone down a lot of rabbit holes and explored a lot of minutiae. (Need an article on, say, the application of French social theorist Michel Foucault’s writings to endurance training? I’ve got you covered.)

But it also means that, in my search for interesting new angles, I sometimes neglect the basics—the bread-and-butter principles that make you faster, stronger, and healthier. This ten-part series is my attempt to correct that omission. Instead of going deep on individual studies, I’m going to synthesize: this is the breezy big-picture advice I would give to a friend on a series of key topics like strength training, supplements, recovery, fueling, and hydration.

Thanks for signing up, and let’s dive into the first topic: endurance training.

The Concept

“Endurance training” can mean a lot of different things, from couch-to-5K to preparing for an Ironman. The details differ, but there are some fundamental principles in common.

There’s a famous equation (sometimes called the Joyner equation after physiologist Michael Joyner) that predicts marathon time from three parameters: VO2 max, lactate threshold, and running economy. Endurance training is the attempt to improve these three parameters. You might do it to become a faster runner or cyclist, or you might do it to improve your health; there’s no better predictor of future longevity than VO2 max, and some scientists now believe that lactate threshold is also a key indicator of metabolic health.

You might also do it—perhaps the best reason of all—because it’s fun.

What the Science Says

The single most important idea to get your head around is your “training intensity distribution.” This is the road map for how much time you spend at different effort levels. If you’re a runner training for four hours per week, for example, you might aim to spend three of those hours running easy, 45 minutes at medium intensity, and 15 minutes hard.

When we read about how famous runners train or famous coaches coach, there’s a tendency to focus on the details of individual workouts. This runner does 10×400 meters with two minutes of rest between each interval, that one takes only 30 seconds of rest. This one does 18-mile long runs, that one does 22 miles. But the individual workouts only have meaning in the broader context of how the week fits together. To understand how a runner trains, I’d rather know their weekly intensity distribution than be given examples of individual workouts.

For novice athletes, the first step is to make sure you have an intensity distribution—that is, that you’re not just doing everything at the same effort. There are a billion ways of breaking down exercise into different zones, including a recent international attempt to agree on a unified five-zone system. The key point emerging from that process is that zones based on a percentage of maximum heart rate aren’t very useful; instead, the most relevant zones depend on whether you’re below, at, or above an intermediate zone we can loosely call “threshold.”

Threshold is the transition point between easy and hard. It’s a simple concept, but the details can get very complicated and be defined in a bunch of different ways: how your breathing changes, what fuel you’re burning, what happens to your lactate levels, and so on. The simplest approach is the Talk Test: if you can speak in complete sentences, you’re in the easy zone below threshold; if you can speak in short phrases with some effort, you’re in the medium threshold zone; if you can only speak in single words, you’re in the hard zone above threshold.

This Talk Test approach is a bit blunt, and it only gives you three zones (easy, medium, and hard). But it’s enough to guide an effective training program, and over time you’ll internalize the feeling of those boundaries so that you don’t actually need to talk to yourself. Eventually, you may want to dial in more precise zone boundaries and subdivide the easy and hard zones to get a full five-zone system—but that’s beyond the scope of Endurance Training 101!

How to Apply It

Now that you have those three zones, how should you divvy up your training? Michael Joyner (of Joyner equation fame) likes to cite the 1964 Olympic 5,000-meter final, where gold went to someone who trained only with short intervals, silver went to someone who did nothing but long, slow distance, bronze went to someone who alternated hard and easy days, and fourth went to someone who did almost exclusively threshold training. The point being: there are many roads to Rome.

Still, I promised breezy and big-picture. The approach I use corresponds loosely to a concept sometimes called “polarized training.” Here, too, there are many nuances and debates about the definition, but the basic idea is that you spend about 80 percent of your training time in the easy zone, and 20 percent in the medium and hard zones. This is something that many novice exercisers (and quite a few experienced ones) get wrong: they think that every run should hurt. Keeping 80 percent of your training easy makes it feasible to gradually increase your overall amount of training, and to recover between hard workouts.

The other distribution that has become very popular in recent years is the Norwegian method. Here the focus is on threshold training in the medium zone: instead of training really, really hard then needing a few easy days to recover, the idea is that staying in that threshold zone is hard enough to make you fitter but easy enough that you can recover quickly. Pros using this approach might do two threshold workouts on Tuesdays (one in the morning, another in the evening), and then do the same on Thursdays, using repeated finger-prick lactate tests to ensure they don’t accidentally drift into the hard zone.

For the rest of us, the takeaway from the Norwegian method isn’t lactate tests and double-threshold days. It’s that workouts at the lower end of the threshold zone offer an optimal trade-off between how much fitness you gain and how much recovery you need. Even though I’d classify my own training these days as “polarized,” I’ve definitely been influenced by the Norwegian approach: in the 20 percent of time when I’m not running easy, I do fewer gut-busting VO2 max workouts and a lot more threshold intervals than I used to.

The key point that I hope you’ll remember: every workout you do, no matter how epic, is just one piece in a bigger jigsaw puzzle. The goal is to accumulate the biggest combination of volume (how much you train) and intensity (how hard you train). Your training intensity distribution is the tool you use to balance volume and intensity in a way that’s sustainable—and hopefully fun—for you.

What’s Next?

Next week’s email is about strength training. Over the past decade, high-level endurance athletes have hit the weight room like never before—and if anything, it’s even more important for long-term health than it is for performance.

Thanks for reading!

Alex Hutchinson