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 runers 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.

Read more

New horizons in iliotibial band biomechanics in runners

The iliotibial band, or IT band, is a thick strip of fibrous tissue on the outside of your thigh. It’s the fifth most common location of injury among runners, and it’s also a very weird anatomical structure.

Two completely different muscles, with seemingly different roles during running, both connect to the IT band: 100% of the fibers of the tensor fascia lata, on the side of your hip, connect to the IT band, but so do about 50% of the fibers of the gluteus maximus (one of the prime movers of the hip joint).

Another strange thing about the IT band is that it seems to be a uniquely human structure: chimpanzees and other primates do not have an IT band (almost all of their gluteus maximus fibers connect directly to the femur, and their TFL muscle inserts on a shorter fascia that terminates above the knee).

Despite its anatomical uniqueness, and its high rate of injury, we—meaning the biomechanical and sports medicine community—don’t really understand a whole lot about what the IT band is doing during running (or walking or cycling, for that matter). All of the most popular “musculoskeletal models” of the body used for gait analysis don’t have a true IT band: they just have a TFL that goes down the side of the leg, and a gluteus maximus that inserts along the femur.

I have just published a new preprint that addresses this problem. The title tells it all: “A full-body musculoskeletal model with an anatomically informed iliotibial band.”

You can read the full preprint below, if you want the technical details, or read on for some highlights on how this model of the IT band works and I think it will be very useful for studying IT band mechanics during running.

đź“„ Read the full paper here

Something to understand: this paper is a beginning, not the end, for my research on IT band biomechanics. The big centerpiece—simulating five gait cycles of running at 8:30/mi pace for one runner—won’t blow you away, though it is a big technical accomplishment, and it  does produce some nice visualizations. This study, and this IT band model, are a foundation for future research (some of which I’m working on already) into many different aspects of IT band biomechanics.

Read more

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!

Read more

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).

Read more

Podcast: Marathon Excellence on Running Book Reviews with Alan and Liz

I was just on the perfectly-named Running Book Reviews Podcast to chat with hosts Alan and Liz about my book, Marathon Excellence for Everyone.

We talk about why I wrote the book, how I approach periodization for the marathon, and how to mentally approach race day, among many other topics.

I really enjoyed this show because Alan and Liz have a huge amount of knowledge about the various ways different coaches approach the marathon and it really shows in the podcast. 

Check out the show on your favorite platforms below! 

🎙️ Listen on Spotify

🎧 Apple podcasts

🖥️ Watch on Youtube

Read more

What can Garmin RunDynamics and Stryd data tell you about biomechanical training load?

I just published a new scientific study—this paper was basically the centerpiece of my PhD dissertation, and the title more or less gives away the premise: “Predicting Achilles tendon and patellofemoral joint forces during running with consumer-grade wearable sensor data.”

In this study, “consumer-grade wearable sensor data” means RunDynamics from a chest-worn Garmin heart rate monitor and similar data from a Stryd foot pod. If you aren’t familiar with these devices, they use on-board sensors to estimate biomechanical parameters like your cadence / stride length, vertical oscillation, ground contact time, and so on.[1]

There are a few issues with the gait metrics you get from these kinds of devices, though. First, are they accurate? And second…do they actually tell you anything about what’s going on inside your body?

Read more

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). 

Read more

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? 

Read more

New app for making power law predictions for race performance

I recently published a critical speed calculator app, which makes it super easy to use the critical speed model to estimate your steady-state max. However, the critical speed model is not the most accurate way to predict race performance at new distances—that honor belongs to power law models (sometimes also called Riegel models, after Pete Riegel who popularized their use in running). 

I covered the science behind power law models in this earlier article on power law models versus critical speed models for predicting race times. Thanks to the infrastructure I built for the critical speed model, it was super easy to swap out the statistical model for a power law model: so now I have a brand-new power law calculator too!

⏱️ Try my power law calculator here ⏱️

Power law models are great for extrapolating—for example, predicting your half marathon time from a 5k and a 10k, or predicting your 400m time from an 800m and a 1500m time. They perform much better at this task than the critical speed model, and my power law calculator also includes some useful features for prediction.

Read more

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.

Read more

Check out my new book on marathon training!