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If you’ve run long enough, you’ll eventually see your race times start to slow, no matter how fit you are and how many miles you log. Maybe you start to notice your legs just don’t spring back from a workout like they used to in your 20s, or your finishing kick feels more like the tortoise than the hare.

Published: 18 October 2018.

Runners World US

“When runners get older, they still want to be setting PRs,” Ray Fair, Ph.D., an economist at Yale University who has been analysing runners’ finish time regression over the years since 1994, told Runner’s World over the phone. “So they get discouraged and pessimistic when they get slower. But in reality, they could be competing at a higher level than they were when they were younger, relative to their age.”

After 40, runners start slowing down - but only gradually study about the effects of aging on runners’ race results, with the goal of finding the precise rate of decline among finishing times. The study graphed the 5K, 10K, half marathon, and marathon results of 200 male runners who ranged in age from 40 to 95 and had set world records in their respective age groups and events.

He entered all of the runners’ world record times divided by event into a quadratic formula and graphed the results. Predictably, it showed an upward slope as runners aged.

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But here’s the thing: runners didn’t start slowing down significantly until they were 40. And when they did start to slow, their decline rate for each race was very gradual. Here’s what Fair’s study found.

Runners maintain speed through their 30s

When analysing age group world records, Fair found no decline in race results of runners younger than 35, and between 35 and 40, runners slowed down by only one percent over the five-year span.

“If you’re keeping in shape and staying injury-free, you’re not slowing down at all before you’re 35,” said Fair. “You don’t see any real fitness declines until age 40.”

So basically, before runners turn 40, the race is up for grabs. This finding isn’t too shocking, considering the ages of podium winners in recent marathons. For example, Mo Farah, who’s 35, won the Chicago Marathon earlier this month in 2:05:11, beating top American marathoner Galen Rupp, 32, who ran 2:06:21.

While the study only used data from men’s races, elite women are similarly stellar even in their late 30s. Last year, Shalane Flanagan won the New York City Marathon when she was 36, beating 35-year-old Mary Keitany. This November, Flanagan is returning to defend her title against Desiree Linden, who’s 35, and Molly Huddle, 34.

The bottom line

The study found that between age 40 and 70, runners slowed by a linear rate of about one percent each year. When runners reached their late 70's, they began to decline by about 1.5 percent, and between 90 and 95, that rate accelerated to two to three percent decline.

“Even at age 90, people are only a little more than twice as slow as they were in their peak years,” Fair said.

Fair, who’s now 76, was an avid marathoner in his middle age. At age 45, he ran his personal best time of 2:58:45 in Philadelphia. Then at 53, he ran a 3:10:00 in Hartford, Connecticut. While the latter time was slower, it was actually a faster time, according to the study’s age-adjusting calculator. If Fair traced a linear slope back from his time at 53, he should have hypothetically ran a 2:58:19—26 seconds faster than his best—when he was 45.

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While we can’t reverse the slow-down effects of aging, we can aim to be the best at every age we reach.

A version of this article appeared on Runner's World US.