Science

New web app: Predicting LT1 pace and Zone 2 pace from 5k time

I’m excited to launch a new app for predicting training paces: my LT1 and Zone 2 pace calculator is now live, and provides a simple and accurate way to estimate your first lactate threshold, or LT1 pace, as well as an upper limit for your easy run pace, a.k.a. Zone 2 pace. 

📲 Check out my LT1 / Zone 2 app here! 

Normally, LT1 requires a standardized blood lactate test for reliable results. But with this app, all you need is your 5k time (or a reasonable estimate of your current 5k fitness).

Under the hood, this calculator relies on real scientific data from thousands of runners and state-of-the-art statistical techniques to come up with its estimates. 

Try out the calculator at the link above, or read on if you want more details on the science behind how it works.

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Designing a plyometrics program for improving bone strength in young runners

Stress fractures are an incredibly frustrating injury, especially for young runners. Even though the science behind recovery from stress fractures—more properly called “bone stress injuries”—has advanced significantly in the last several years, sustaining a bone stress injury can still completely derail your season.

Of course, far better than a swift rehabilitation is simply not getting a stress fracture in the first place (or at the very least, avoiding another one). That’s what we’re concerned with today.

Thanks to advances in the fundamental science of bone injuries, we now know that a powerful lever at your disposal for increasing your resistance to bone injuries is improving your bone strength. The best way to do that? Targeted plyometric training, a.k.a. “jump training.”

This kind of high-load, high-loading-rate intervention is especially effective at improving bone strength in young runners—roughly, teens and pre-teens, with some wiggle room on either side for individual differences in puberty and growth spurts.

However, if your goal is building bone strength, you should not use a general-purpose, performance-oriented plyometrics program for runners. Plyo programs that target bone strength need markedly different components for maximum efficacy.

Below, I’ll walk you through the science behind building a plyometrics program for bone strength, including total contacts, types of jumps to include, and appropriate programming during the week.

If you just want to get the final plyo program as a printable PDF, you can download it here: 

đź“‹ Download the bone strength plyometrics program here

Otherwise, read on to learn the science and practical programming behind this plyo routine!

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Three theories of tissue damage accumulation during running

Suppose you need to run 15 miles (24 km) in the next week. You can distribute this volume however you want, both within and across days. Your goal is to cover the requisite distance in a way that minimizes your risk of injury. Does it matter how you schedule out your week?

This is one concrete way of thinking about the question of cumulative damage in running: given that you’re going to cover some combination of distances and speeds, does the ordering affect how much tissue damage you’ll accumulate?

We’ll look at three different theories on how tissue damage accumulated during training. These aren’t exactly competing theories—more than one can be correct—but considering each framework separately helps sharpen up how you think about programming your training.

I think all three have some truth to them, though I’m still skeptical of the strongest version of each of the three (and I’ll explain why).

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Lecture: The science behind modern marathon training

John Davis lecturing about marathon science

I just posted the video from my live lecture on the science of modern marathon training! 

In the video, I uncover the science behind the modern approach to marathon training, including how VO2max, running economy, lactate threshold, and physiological resilience each contribute to marathon performance. Then, I explore the training methods that most effectively target each of these components of marathon fitness. 

The Q&A session at the end covers lactate shuttling, glycogen depletion, periodization, and long-term development, among other topics. 

Here’s the full video—be sure to like the video and subscribe to my YouTube channel if you want to see more video-based content in the future. 

You can watch the embedded video above, or watch it here on YouTube. There is some material that’s easier to convey in a lecture or video, so I’m hoping to do more video content in the future (don’t worry, I’ll still be writing plenty too). 

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What assumptions are baked into your race prediction model?

After launching my power law calculator earlier this week I got a couple emails from readers who noticed some counter-intuitive behavior.

Suppose you have an athlete who has run 800m in 2:25 and 1600m in 5:10. The power law calculator predicts a 3200m performance of 11:03—pretty reasonable. 

Then suppose your athlete improves their 800m time to 2:20. Enter that into the calculator instead and you get a 3200m time of 11:26—which is slower than their predicted 3200m time before! This seems wrong: shouldn’t the runner now be able to run faster over 3200m as well?  

Now, this wouldn’t be the first time a reader spotted a subtle issue with one of my calculators, but in this case, the calculator is working correctly, under the assumptions baked into the model. Here’s the intuition: 

Suppose you had two different athletes: Fast-Twitch Frannie, who runs 1600m in 5:10 and 800m in 2:20, and Slow-Twitch Sally, who can also run 5:10 for 1600m, but can only run 800m in 2:25. If these two athletes race over 3200m, who will win? 

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Tendons do not store energy for free

Very often, in training discussions online and in books—even sports science textbooks—you encounter the claim that, during running, tendons stretch out and store up energy on impact with the ground, releasing that energy later when you push off the ground. This energy storage improves your running economy, because without it, you’d have to produce that same force via the active contraction of your muscles. 

The “tendons store energy for free” claim is used to justify doing plyometric training, heavy load weightlifting, or hill sprints, with the goal of increasing this energy storage and improving your running economy.

However, this claim is wrong—tendons do store energy, and a stiff, strong tendon does improve running economy, but this energy storage does not happen “for free.” The reasoning is quite obvious when you analyze the biomechanics behind tendon energy storage. In this post, we’ll consider the case of the Achilles tendon, but the argument also applies to most of the other major tendons of the lower body.

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In windy conditions, running at a constant effort is usually better than running at a constant speed

Suppose you are running a 5k race on an out-and-back course, and there’s a strong headwind on the way out—should you aim to run at the same effort the whole way, allowing the wind to slow you down on the way out and speed you up on the way back? Or should you maintain the same speed, working harder on the way out and relaxing more on the way back? 

For most runners, it feels intuitive that constant-effort running should be better—in the sense of leading to better performance—than constant-speed running: constant-effort pacing is better than speeding up and slowing down, after all. But here’s a potential counterargument: if you run faster when going into the wind, you spend less time exposed to the wind, so you’ll save energy on balance.

So, which argument is correct?

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A comprehensive guide to the science of cadence for runners

Your cadence is the number of steps you take per minute while running. Simple measurement, right? But there are many questions surrounding it, including how it differs across runners, how it changes as you run faster, whether a higher cadence is more efficient, whether a lower cadence causes injury, and whether you should aim for a specific number.

It almost goes without saying that there is an enormous amount of erroneous information circulating around when it comes to cadence, to such an extent that—with a few exceptions—I’m mostly going to avoid trying to refute everything wrong about cadence you may have seen elsewhere, and instead focus on the (correct) biomechanics of cadence in running.

Cadence is squarely in my scientific wheelhouse; I spent most of my time during my PhD collecting and analyzing biomechanical data. One of the chapters of my dissertation is even focused on the merits of cadence (and other gait metrics) as a predictor of biomechanical loading. So, buckle up—we’ll be covering everything you need to know about cadence.

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Understanding tissue loading, tissue damage, and running injuries

In my article on biomechanical training load, I covered the basics behind how biomechanical loading is related to the development of running injuries.

The basic idea is pretty straightforward: every time you take a step, your tendons, bones, and joints experience a loading cycle: a build-up and release of mechanical force.

Each loading cycle does a tiny amount of damage, depending on the magnitude of the force and the structural integrity of the tissue. If this damage accumulates faster than your body can repair it, the result is an overuse injury.

In this article, we’re going to take a deeper dive into exactly how this process of tissue damage works. Our goal is to build up an understanding of cumulative damage: a way of quantifying “how much damage” you’ve done to a specific piece of tissue.

We’ll use the recurring example of damage done to the Achilles tendon, since it’s a common injury and a relatively straightforward tissue in terms of understanding both its biomechanical loading and its tissue properties.

So, what is the actual mechanical process behind tissue damage in running? Let’s dive in and find out.

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A high-level picture of biomechanical training load for runners

What do we mean when we say “training load”? This is the second article in a three-part series aimed at answering that question.

My core argument in this series is that there are three distinct types of training load you should consider—physiological training load, biomechanical training load, and psychological training load.

Today, we turn our attention to the second of these types of load. What exactly is biomechanical training load? In short:

Biomechanical training load describes the mechanical force—and ultimately, the mechanical damage—experienced by the load-bearing tissues of your body: bones, tendons, muscles, ligaments, and joint surfaces.

When talking about biomechanical training load, what we mean is “how much physical damage are you doing to your body.”

Proper biomechanical training load drives health and structural integrity: the ability to avoid injury and increase your body’s ability to sustain higher levels of training in the future.

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Check out my new book on marathon training!