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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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.

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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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New web app for calculating critical speed

When I published my detailed write-up on the science of critical speed for runners, I promised that I would code up a free calculator to calculate your critical speed (also known as “critical velocity” or CV) from a set of race performances. That calculator is now finished! 

⏱️ Try my critical speed calculator here! ⏱️

This free web app makes it super easy to implement the statistical calculations that give you critical speed—and its uncertainty bounds—given a set of race performances.  

Like all of my web apps, it’s designed to be mobile-friendly, and it includes cookie-based “memory” so you can come back to where you left off. This critical speed calculator is also super easy to use: you don’t have to convert race performances into seconds, and you can choose from a wide range of pre-set race distance options, or enter a custom distance.

This is the only critical speed calculator I know of that gives you statistically appropriate uncertainty estimates that you can use for physiologically based workouts. 

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Chatting marathon training, strength work, and mindset with Alec Blenis

Recently I sat down to chat about training with hybrid athlete, coach, and content creator Alec Blenis. This was a particularly interesting conversation because I am also coaching Alec on his quest to break 2:30 in the marathon while maintaining his strength and physique goals. 

I’m always looking to learn new things as a coach, and working with Alec, who is very knowledgeable about strength training, is a great opportunity for me to learn how to integrate marathon training and serious strength work. 

Check out the video below!

We had an excellent chat about marathon training, strength work, mindset, my thoughts on current trends in training, and my opinion on the greatest marathon ever run. 

If you enjoyed this conversation and want to follow Alec’s training, be sure to follow him on Instagram, like the video, and subscribe to Alec’s YouTube channel. These are super easy and helpful ways to show content creators that you appreciate their work! 

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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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Live Lecture: The Science of Modern Marathon Training on April 30 in Minneapolis, MN

I’m excited to announce my first live event: a public lecture and Q&A on the science of modern marathon training. 

In this 45-minute talk, we’ll dive into the latest scientific findings on marathon performance and how you can use these findings to improve your training. There will also be a Q&A session and a book signing + informal chat afterwards where you can get answers to your burning questions about your spring marathon preparations. 

Join me Thursday, April 30 at 6pm in Minneapolis, Minnesota to see the lecture in person! Tickets are $25, sign-up at the event page here or use the button below.

Get Your Tickets Here

Tickets are limited so sign up early to reserve your spot. The event is being hosted at Open Book in downtown Minneapolis, home of the Loft Literary Center.

Signed copies of my book Marathon Excellence for Everyone will be available for purchase at the book signing afterwards (you can of course bring your own copy as well).

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New calculator for track workouts on windy days

I just released a brand new web app for track workouts and races on windy days! 

A common challenge when doing track workouts or races is non-ideal wind conditions. This calculator applies the same validated scientific model from my wind-adjusted pace calculator to the specific geometry of the track. 

Scientifically speaking, this is probably the most advanced calculator I’ve ever made, and yet it’s still super easy to use. All you need to know is your pace (or calm-day effort level), the wind speed, and the wind direction. Everything else is taken care of by the web app!

🍃 Check out my new wind calculator here! 🍃

This app uses state-of-the-art biomechanics and physiology data, alongside a rigorous mathematical treatment of track geometry, to accurately account for the turns on an outdoor track.

My new app even supports “non-integer lap” distances for workouts like 200m, 600m, or 1k repeats (a favorite trick of mine for dealing with windy days at the track).

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Coe-style elite 800m, 1500m, and mile training from “Winning Running”

If you want to understand training for middle-distance running events—800m, 1500m, 1600m, mile—you need to understand Peter and Sebastian Coe’s approach.

In the English-speaking world, Coe-style training absolutely dominated discussions about training in the 1980s, 1990s, and early 2000s, mostly due to the fact that Sebastian Coe, under the guidance of his father Peter, was the king of the 800m, 1500m, and mile in the 1970s and 1980s.

The analogy to the Ingebrigtsen family is obvious: a father with a bold vision for training and a son with incredible talent and grit, who not only rose to the top of the sport athletically but changed the way legions of runners approach training for their event.

Both coaches borrowed heavily from a pioneering compatriot—Gjert Ingebrigtsen from Marius Bakken,[1] and Peter Coe from Frank Horwill. Like Jakob Ingebrigtsen and Josh Kerr, Coe also had fierce rivals: fellow Brits Steve Ovett and Steve Cram, each of whom snatched medals from Coe in dramatic fashion.

That’s where the similarities stop, though—Sebastian and his father never had a falling out, and the structure of Coe-style training is almost diametrically opposite to that of Ingebrigtsen-style training.

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Check out my new book on marathon training!