Average race times are increasing in every distance, every age group, and for both genders. But the question is why?

By Charlotte Hilton Andersen

Runners across America are getting slower-much slower, according to a recent analysis by Jens Jakob Andersen, Ph.D., and Ivanka Andreeva Nikolova, Ph.D., from the Copenhagen Business School. The researchers say that American runners are getting less healthy and that's affecting race times.

Andersen, a former competitive runner himself, noticed that while more people were getting into racing during the last two decades, they didn't seem to be getting much faster. Curious to see if the data would support his observations, the statistician partnered with Nikolova, a mathematician, to analyze data from more than 34 million finishers, both men and women of varying ages, of 28,000+ races between 1996 and 2016. Race distances included marathons, half marathons, 10Ks, and 5Ks, and the truth was in the numbers. Every year since 1996, average finishing times for each distance in each category were slower than the year before, says Nikolova. And marathon finishers are about 35 minutes slower than they were 20 years earlier, while half marathon times increased by an average of 43 minutes since then, 10Ks by 24 minutes, and 5Ks by 10 minutes. (There is one exception, though: Elite runners continue to smash world records.)

But are these slower times really indicative of a massive public health problem or is it just evidence that more and more people are lacing up and racing, and naturally dragging the average pace down? After all, running has been the most popular form of exercise for more than two decades in this country, according to previous research, and the surge in popularity could inspire beginners and less-fit people to sign up for a race, which is a good thing.

"This is a popular myth but it's not true," Nikolova says. "Americans are getting slower across all of the major race distances. Everyone's speed is suffering-men and women, fast and slow." She says the data simply doesn't agree with that theory, pointing out that race participation declined in 2015 and 2016 and yet finish times still continued to increase.

Another common argument she says is that more women than ever are running, and because women are generally slower than men (pssh), it's pulling the average time down. Not only did the gender-specific data show that both women and men were getting slower, but Nikolova and Andersen found that men are getting slower at a quicker rate than women are. In fact, the difference is so stark that Nikolova predicts that by 2045 men and women will have the same average finishing times. (Read this open letter to runners who think they're too slow.)

She also says the data disproves the argument that it's just the slowest that are getting slower or that more people are walking in races. Instead, race times are actually increasing in all different speed categories.

While there is still room for many other factors, all this data diving led them to come to the unsettling theory that it's the American people's worsening health that's slowing them down, says Nikolova. To verify the correlation, the researchers looked at health data during a portion of that same time period and found an increase in obesity, diabetes, and hypertension during the years 2000–2016. The researchers then comapared race times during this same time period and found that the speed was particularly slow for shorter races, such as the 5K and 10K. Essentially the rise of health issues such as obesity ran somewhat parrallel to the rise of finish times for these shorter races.

"Signs of poor health are highly correlated to the decrease in speed," she explains, adding that this doesn't necessarily mean that poor health or one of these particular conditions would directly cause someone's speed to decrease.

None of this is to say you should give up running or worry if your pace is slowing. Running is great exercise that has significant mental and physical benefits no matter how fast you do it. (Research has found that running just two hours a week could even help you live longer.) Rather, Nikolova and Andersen say this should be a wake-up call that you need to pay just as much attention to other aspects of your health like nutrition, regular checkups, and getting enough sleep. Bottom line: You can't outrun an unhealthy lifestyle.


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