The 80-20 rule in athletic training* goes like this: train 80% of the time at a low intensity and 20% of the time at a high intensity, and you’ll achieve the best results.
Understandably, a lot of people—particularly us urbanites who are extremely busy and almost completely devoid of free time—might say: “but I only have a few hours to spare every week! I can’t afford to run slowly 80% of the time. How can I possibly expect to make gains?”
(Or something like that.)
This is exactly the wrong question. What running (a.k.a. training) at a low relative intensity—which people often refer to as “running slowly” does for the body is that it develops the aerobic system. (For most, but not all of us, training at a low relative intensity does indeed mean running slowly.) The aerobic system is extremely important: it mitigates oxidative stress (also known as chemical aging), it helps us recover from anaerobic efforts by processing lactate, and it keeps us well-fueled over the long-term by burning fats.
The aerobic system is the very foundation upon which any “gains” are built. In this sense, aerobic training increases what I like to call our “physiological capital,” that we can invest in high-intensity (anaerobic) training and develop what we typically refer to as “strength” and “power.”
To explain this relationship, I like to use the metaphor of a Jenga Tower.
Suppose that you have a particular strength or power goal: you want to run 6 minute miles. This is equivalent to wanting your Jenga tower to be 10 levels tall. But the problem is that you only have 20 bricks (each full level of a Jenga tower is 3 bricks).
The result is that you can only build 6 complete levels to your Jenga tower. You’re faced with a stark choice: you need to add levels to get to 10. But you don’t have any more bricks. So you’re forced to take from the lower levels. (This is essentially what strength training does). Your tower gets higher and higher—which is fine, until you pull out or lay a brick juust too quickly or a light breeze comes along—and the tower, which had grown increasingly unstable, plummets to the ground.
(You’ve just become injured.)
But there’s a way to add bricks to the base of your tower: aerobic training. This is what I mean by “increasing our physiological capital.” While aerobic training adds bricks at a pretty good rate, left to its own devices it turns your tower into a pyramid: the lowest level grows wider, until at some point your body decides to start growing the next level.
That’s not a bad thing: a lot of ultrarunners (the healthy ones) have metabolisms that look like a shield volcano: gargantuan aerobic systems, but very little power. (If the height of the tower is how much power you possess, then the width of the base is how much distance you’re good for.)
That said, it’s not necessary to build a pyramid, when it’s a tower you want. Although it’s important that your tower be stable, that’s about it: most of us are not trying to be an ultrarunner, nor do we have to be. All you really need is a few extra bricks around your base—enough to plug any holes you may have created, and to be able to add a couple of levels. Rinse and repeat.
A quick disclaimer: the body doesn’t convert the actual aerobic machinery into anaerobic machinery in the way that a naïve reading of the “Jenga metaphor” would suggest: the brick that you take from the base is not literally the same one you put on top of the tower. However, the reason I like the Jenga metaphor is because the stress and wear-and-tear incurred by anaerobic work (compounded by the fact that it is the job of the aerobic system to absorb those stresses), means that the process of adding strength and power basically always means carving into your aerobic base.
How often do you switch from adding bricks to adding levels? If you’re looking to run an endurance race, for example, then you need a very wide aerobic base.
Supposing that you want to develop some all-around fitness, a basic (but certainly not universally applicable) recipe is this:
- For 2 weeks, train primarily easy 95-100% of your training.
- The next 2 weeks, train at a moderate-to-high intensity 35-40% of the time.
- Rinse and repeat.
This process will give your body two weeks to recover well from strength training (read: replenish the bricks you took from the base, and add a few more). Two weeks of low-intensity training isn’t really long enough to start losing high-end fitness: the small amount of strength training 0-5% during the easy weeks is more than enough to maintain your gains. But when you’ve cycled through this process several times is when you’ll really start to see your gains stack up.
Building and maintaining an aerobic base, and making sure that our strength gains are well-buttressed by wide lower levels of our metabolic tower, is non-negotiable. Some of us are lucky: for good or ill we spent our formative years playing at the beach, kicking around a soccer ball, or going hiking with our oudoorsy parents. This person (unbeknownst to them) has been stacking more and more bricks around the base their fledgling tower, broadening their aerobic base until they’ve accrued what seems like a limitless amount of bricks.
Others never had that chance.
But not having had that chance doesn’t mean we have any more of a choice. Sometimes, the unconscionable choice—running “slowly” despite the horrible feeling that time is slipping away and we’re not getting any faster (forgetting the fact that our pool of bricks is growing ever larger)—is also the right one. That choice will put us in a position from which we can develop speed . . . and get to keep it.
*NOT the Pareto Principle.