Why Are Americans Getting Slower? A Look Into Running’s Largest Study With Jens Jakob Andersen

That’s a sensational title, but hear us out.

A study published by RunRepeat.com, an independent review aggregator for running shoes, analyzed 34,680,750 race results over the course of 21 years to conclude that American runners are steadily getting slower across distances from the 5K up to the marathon.

We know what you’re probably thinking: with Olympians like Galen Rupp and Molly Huddle continually setting national records, how can that be?

While it’s clear US elites are steadily advancing, the study found that the remainder of the field is, on the whole, slower than it was in the 90s.

Now this could be due to a variety of reasons, and some argue one of those reasons might just be that the sport has gained a lot of popularity in the last couple decades.

More runners of varying age and gender? We like the sound of that.

While this is certainly plausible, others argue there’s another, less favorable culprit behind the trend: the rising rate of obesity in America.

This is the hypothesis behind the study in question led by Danish statistician, runner, and founder of RunRepeat.com Jens Jakob Andersen.

While Jens believes the correlation between slowing race times and deteriorating health in America is too close to deny, he’s quick to remind us that correlation is not causation.

When it comes to statistics, Jens says it’s always easier to debunk something that’s not true rather than prove something that is, and that’s exactly what he aims to do in this episode.

Listen in and decide for yourself. Whichever way you end up leaning, you’re bound to learn something interesting about yourself and your fellow runner along the way.

. . . . . . . . . .

Correction: At 15:57, Jens mistakenly states he and his research team determined “walking pace” to be 9:30 minutes per mile. He meant to say 19:30 minutes per mile.


Questions Jens is asked:

2:28 What first sparked your passion for running?

4:30 What prompted you to start RunRepeat and what does your day-to-day entail?

7:02 How is RunRepeat’s Run Score calculated?

11:23 How should runners go about choosing a shoe that’s really right for them?

12:32 What did you find in your study of American runners becoming slower and what do you think the implications are?

21:43 Could it be that there just aren’t as many Americans in the top 1% to compensate for the greater number of people towards the back of the pack?

23:38 What would it take for Americans to reverse this trend?

27:02 Where are some of these Blue Zones located?

27:41 In your study on marathon results, what were some of the key takeaways you saw and what did the study entail?

31:58 Why do you think there has been such an increase in female runners over 50 taking up running within the last decade?

33:38 Why do you think men tend to go out faster than they probably should when racing?

35:38 Why do you think runners ages 35-45 make the best pacers?

37:02 Based on the studies you’ve done, what advice would you give us on tackling our next marathon?

39:42 What’s next for you at RunRepeat?

Quotes by Jens:

“It bothered me how 90 percent of people bought the same five pairs of running shoes, and I thought, ‘Why is this happening?’ It’s happening because these brands…promote specific models, and so there becomes a hype around specific models.”

“We looked at the finisher number (number 100, number 1,000, number 2,000, number 5,000) for each race distance, and what we found was that across this all were getting slower.”

“It’s always hard with statistics to come up with a clear cut conclusion. It’s always easier to debunk something that’s not the case.”

“Americans (as well as most other nations) are getting more and more obese, and their finish times are getting slower. But this is a correlation: two parameters that follow each other. It’s not necessarily a causation….So this is our hypothesis, but we cannot conclude it for sure with 100 percent certainty.”

Take a Listen on Your Next Run

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Mentioned in this podcast:

RunRepeat Article: American Runners Have Never Been Slower (Mega Study)
RunRepeat Marathon Study
RunnersConnect Race Pace Calculator
NPR Article: Longevity Diet Tips From the Blue Zones
Follow Jens on Twitter
Send Jens an email

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3 Responses on “Why Are Americans Getting Slower? A Look Into Running’s Largest Study With Jens Jakob Andersen

  1. I feel deflated when your guest said 9:30 min/mile pace is considered walking! I know I’m a beginner, but that has been around my half marathon race pace. I belong to a USA Fit Run group in my area and I am about mid-pack in my group but there are many of us in that mid pack group. Do you mean to tell us that we are all walking, not running? Sure doesn’t feel like it. During our track workout, I can run about a 7:30 min/mile, but certainly not during a half or full. Not even a 10K. I’m wondering if your podcast and website is really meant for only upper eschelon runners. I am an avid listener of you podcast and have enjoyed it for the wealth of information and wonderful guest, but when I heard that I am considered a “walker” I just got disheartened.

  2. Hello, I emailed Jens Jakob Anderson directly and he clarified his statement. He meant to say 19:30 min per mile which makes way more sense. I am relieved!

    Thanks again!

    • I apologize for the mistake and am so glad you emailed Jens to clarify that. 9:30 is a VERY impressive pace for the half marathon. Hell, that’s an impressive pace for the 10K! Not sure how I missed that, but I appreciate you catching it and bringing it to our attention. I’m going to add a correction to both the interview and show notes today to prevent any further confusion.

      Thanks so much again for pointing this out and for tuning in each week! Knowing the podcast is helping runners like you toward their goals is what makes my job so gratifying.

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