The athlete had dedicated nearly his whole life to a single pursuit, made the Olympics before he could drive, but was not satisfied there. No, that only whetted his appetite for the top of the mountain. He trained through the years when his peers were partying in college, through success and failure, through an alcohol abuse problem, through fatherhood and becoming a devoted family man. And then, in Rio, he lined up for the last time, shaking out his muscles, staring at the end of a journey, this wisened old athlete, at…31?

You might have guessed that we’re talking about Old Man Phelps. As a Washington Post headline read: “Michael Phelps faces his toughest challenger yet – age.” Given that the hourglass sands were fast slipping through Phelps’ webbed fingers (kidding), it is no surprise that 35-year-old swimmer Anthony Ervin never stood a chance. Ervin won gold in the 50-metre freestyle at the 2000 Olympics in Sydney, then in 2003 started about a decade (!) off from swimming, in which he got out of shape and moved to Brooklyn to – what else? – jam with a band.

He came back around the start of 2012, and got in shape so quickly that he qualified for the London Games, finishing fifth. In Rio, at 35, he made Phelps look green. It was heartwarming to see an athlete so long in the tooth willing to give it a last go. (Cue NBC human interest muzak here.) His motivation, though, is understandable.

As Brick Pollitt – Tennessee Williams’s shambling ex-football hero in Cat on a Hot Tin Roof – put it: “People like doing what they used to do, after they’ve stopped being able to do it.” It’s just that, Ervin’s “used to” is winning the gold medal in the 50-free, and that’s exactly what he did again in Rio. Old people are so cute.

Then there was 100-meter sprinter Kim Collins, of St Kitts and Nevis, who ran under 10 seconds this year – he’s 40. Two US medal hopefuls, Meb Keflezighi in the marathon and Bernard Lagat in the 5,000 – are 41. And cyclist Kristin Armstrong won the gold a day before she turned 43. So, perhaps we should hold off on letting her know that she’s supposed to be expired.

This isn’t strictly a new phenomenon either, or some creation of modern sports medicine: legendary Hawaiian swimmer Duke Kahanamoku won a silver in the 100 free at 33, in 1924. In 1972, two 40-year-old runners finished third and eighth in the men’s marathon. Gordie Howe played professional ice hockey into his 50s.

Just a number

The ubiquitous commentary this Olympics about athletes battling age – most prominently, Phelps – doesn’t represent the reality of aging Olympians. There is no necessity for physical prowess to disappear by 30, and that’s critically important for all us non-Olympians to know. To some degree, physical aging is a choice. It’s a mistake to base our concept of physical aging on the age that Olympians retire, since many – perhaps most – retire for reasons unrelated to physical deterioration.

Old ideas about amateurism in Olympic sports didn’t fade until the 1970s and ‘80s, so there was no way for most athletes to support themselves while training full time after their early 20s. Mark Spitz retired at 22, not because he’d lost it. (He was still pretty fast when he came back at 42.) Still today, most hopeful Olympians struggle to find ways to support their competitive careers after college. (One of the authors of this piece trained in college with a runner who was offered a spot on a team that developed potential Olympians. His other post-college option was Teach for America. Only one of those offered him a way to pay his rent, and that was the end of his running career.)

Outside of the US, the situation is often even more difficult, as no other country has a college sports system that provides teams and competitions for hundreds of thousands of athletes through their early 20s.

This is not to say that advances in sports medicine have not helped – they have. The poster athlete for that being Tommy John, who pitched in the Big Leagues until age 46, 15 years beyond surgery to repair a ligament in his left elbow. Olympic champion skier Hermann Maier of Austria nearly died in a motorcycle crash, but returned to elite skiing through his late 30s. Additionally, burgeoning knowledge about the science of rest and recovery is helping athletes extend their peaks. But it’s probably safe to say that few of the television commentators holding forth about age have delved into the actual science. So what do we actually know about aging athletes?

Why does it seem like sprinters age faster?

First, keep in mind that Usain Bolt is 30 on Sunday, and Justin Gatlin, who took second in the 100, is 34. (Gatlin missed his late 20s in competition as he was serving a doping ban.) Still, it is true that, as we age, our type II – or “fast twitch” – muscle fibers, the kind most helpful for explosive movements, shrink more rapidly than type I – or “slow twitch” – muscle fibers. So we should expect to see a younger average age in the 100-metre dash than in some endurance events. And that is, in fact, what we see.

The average age of 100-metre medalists between 1984 and 2012 was around 25. But in the first half of the 20th century, it was a few years younger, so that age has crept up, and this year Kim Collins was the first 40-year-old to run under 10 seconds.

So how old can endurance athletes be?

Depends what you mean. Canadian Ed Whitlock is 85, and earlier this year ran 1:50:47 in the half marathon. That’s around eight-and-a-half minutes per mile for 13.1 miles. And we repeat, he is 85! (And he was bummed he didn’t hit his goal of 1:45.) Whitlock had been a competitive runner in his teens, but stopped, became an engineer, and picked it back up in earnest in his 40s.

For an athlete who intends to maintain elite performance – not just elite-for-age performance – that kind of multi-decade break won’t do. The key for an aging Olympian is to keep up their training intensity, while avoiding injury. That may mean they take more recovery days, run in water instead of on the ground, or simply compete less often. (Usain Bolt is a pro at competing less often. He skips the entire indoor track season, and makes himself scarce in years without Olympics or World Championships.)

A remarkable study of Danish rower Eskild Ebbesen shows just how well an athlete can age. Danish sports scientists studied Ebbesen between the ages of 19 and 40, as he competed in five Olympics (1996–2012), medaling in every one. Over that time, they saw Ebbesen’s maximum heart rate decline markedly. If his heart wasn’t beating as fast, it stands to reason he wasn’t moving as much blood, and therefore oxygen, to his muscles. But in fact his ability to move oxygen stayed completely steady.

The scientists found evidence that Ebbesen’s body was compensating for fewer heart beats by pumping more blood with each beat. They saw that Ebbesen’s left ventricle – the heart chamber that takes blood that has been filled with oxygen in the lungs and pumps it to the muscles – had enlarged from his training. By keeping his workout intensity up, Ebbesen was exactly able to offset one physiological change of aging with another that came through his training.

Are medalists still getting older?

There are actually events where many elite competitors have gotten younger. The marathon used to be seen as an event for athletes who no longer had enough speed for the track. That’s no longer the case, and because major marathons offer large cash prizes, younger athletes turn out. But so too do older athletes, like 41-year-old American Meb Keflezighi, who won a silver in 2004 and will run the marathon on Sunday.

Athletes have tended to get younger in women’s gymnastics as well. (The sport has even had scandals when someone lies about an athlete’s age to make them seem older, and thus eligible for elite competition.) That’s primarily because, as aerial routines have become more difficult, it benefits gymnasts to be smaller.

But there was a 41-year-old gymnast in Rio, in her seventh Olympics. And, in a few men’s sports and most women’s sports, the medalists have gotten a bit older. Women who medal in sports that require power and endurance, from sprinting and swimming to speed skating, now tend to be in their early to mid–20s.

Prior to passage of Title IX in 1976, women who medaled in those sports were more often in their late teens or very early 20s. One group of researchers noted that Title IX had a global ripple effect; it provided more opportunities for sports participation for American women, and as they got better, other countries started creating more opportunities to ensure that the US didn’t run away with the entire Olympic medal stash.

Those researchers also have data suggesting that, while medalists in running and swimming still have an average age in their early-mid 20s, there is more regular appearance of age outliers, like Jamaican legend Merlene Ottey, who won bronze in the 100 in Sydney at age 40.

What about older athletes?

Excellent or horrific news, depending on how you look at it: Highly trained 80-year-olds can have exercise capacities on par with sedentary 20-year-olds. (The bad part is that many 20-year-olds are basically equipped with bodies they don’t know how to use, which is reflected in average fitness levels.)

That means, very roughly speaking, they could run about the same time for a mile. In a study of nine Swedish men (including an Olympic champ and several national and regional champs) who had trained in cross-country skiing consistently for at least 50 years, the men’s aerobic capacity (again, how much oxygen they can move at max effort) looked roughly similar to what you’d expect from a group of healthy but untrained young adults, and these men were in their ninth decade of life.

A comparison group of six octogenarians with no history of training looked far worse. Two of them were barely above a level of aerobic capacity below which they really couldn’t live independently.

But wait, it gets cooler still for lifelong exercisers. We spoke with Dean Kriellaars, a physiologist who works with Cirque du Soleil, and he’s been tracking some rather astounding data for performers. Typical medical dogma is that bone density peaks in adults between the ages of 25 and 30, and then all you can do is use resistance training to slow the typical decline of about 1% a year (and 2-4% for women post-menopause).

“In our men and women who perform,” Kriellaars said, “we find that there’s almost no loss at all up to 65. It’s almost a flat line up to 60 or 65, certainly to 60.” These are lifelong athletes, who perform hundreds of shows a year, and Kriellaars is specifically speaking of performers with physically rigorous circus roles, as opposed to, say, musicians.

As they head toward 60, the performers do lose some muscle, but not nearly so much as the general population. “We see a very slow decline,” Kriellaars said, “but not nearly the decline that [doctors] say will happen normally.”

Fat is a little trickier. Kriellaars said that the performers do gain fat as they age, even while remaining active, so that might be less easy to alter with training, but, again, it’s not nearly as rapid a gain as the general public. And this may be the most important thing to remember: you don’t have to be a complete workout maniac to get a hefty dose of these benefits.

Kriellaars noted that a typical physical activity recommendation for kids is an hour a day, every day, of moderate to vigorous activity – that’s 420 minutes a week. He said that about 40% of kids under 11 meet that, while only about 3-5% of adults reach the recommendation of 150 minutes, or a half hour five times a week.

The Cirque du Soleil performers hover around 270 minutes per week, including performances. (Their activity is precisely tracked with biometric vests under their costumes.) Two-hundred-and-seventy minutes is significant, nearly double the recommendation for adults. But it’s not outlandish, and it’s far less than the recommendation that many kids meet. These aren’t “circus freaks,” as Kriellaars put it, they’re just very consistent. One very acrobatic performer in her late 50s does essentially the same routine as one who is 20.

In the few remaining days of the Olympics, keep an eye out for “old” athletes, and you might notice that they’re not as rare as you thought.

This article first appeared on ProPublica.