Katie Ledecky collects the Phillips 66 Performance Award for her victory in the 400m freestyle during the National Championships & World Championship Trials earlier this month. (Tom Pennington/Getty Images)

On the one hand, Katie Ledecky is among the most predictable swimmers ever to dip her toe in the pool. She’s both efficient and consistent, from humdrum early morning practice sessions to the biggest meets on the planet, her effort and mechanics seemingly cut-and-pasted from one to the next.

On the other, no one can say for certain what her future holds. At 20, Ledecky is at a point in her career when many elite distance swimmers are either peaking or past their primes, a year or two removed from their best performances. But Ledecky, with a storage unit chock-full of records, medals and honors, already has shown that it’s unwise to use the past as any sort of measuring stick for the future.

“It’s so unpredictable,” said Russell Mark, USA Swimming’s high performance consultant. “I don’t know what the limit is for her. Every time we see her swim, you get a little more surprised at how much faster she is. I don’t know that we’ve seen the ceiling.”

Ledecky will have another chance to show just what’s possible in the pool at the FINA world championships, which get underway Sunday in Budapest. Ledecky is expected to compete in four individual events — the 200-, 400-, 800- and 1,500-meter freestyles — and two freestyle relays — the 4x100 and 4x200. If she somehow brings home six golds, she would tie Missy Franklin’s record for world titles by a female swimmer.

Fans cheer for Katie Ledecky at the Women's 400 LC Meter Freestyle Final during the National Championships & World Championship Trials. (Tom Pennington/Getty Images)

While some of her predecessors in the distance races might have posted their best times as teenagers, Ledecky has shown signs that she’s only getting faster. After her freshman season swimming for Stanford, she posted strong times at the U.S. national championships last month, all similar to her marks at the U.S. Olympics trials 12 months earlier. But making her most recent times more impressive: She barely tapered before arriving in Indianapolis. She had planned her summer around Budapest, and few would be surprised if her times this week rival some of her best marks.

While some sprinters might peak a tad later than their distance counterparts, elite swimmers of all stripes often post their best times in their teens and struggle to match those marks as they age. That description includes Amanda Beard, Katie Hoff, Kate Ziegler, Ye Shiwen and even Franklin.

Ledecky holds three world records that were once owned by Janet Evans. Three decades ago, Evans posted her best 1,500 time at age 16, best 400 time at 17 and best 800 time at 18. Ledecky not only topped all of Evans’s best marks, as her teenage years wound down, she continued lowering the times, effectively swimming against herself and history at each world championships or Olympics. Ledecky set the 400 record when she was 17 (and lowered it twice since), the 800 mark when she was 16 (and lowered it four times since) and the 1,500 record when she was 16 (also lowering that one four more times).

“Katie is so special and unique. She is a Michael Phelps,” says Rebecca Adlington, an Olympic champion in the 400 and 800. “She is rare, and I doubt we’ll see anyone like her for a long time.”

Adlington held the 800 world standing until Ledecky, 15, took the British swimmer’s record at the 2013 Barcelona world championships. Adlington had retired from the sport six months earlier and noted that “female distance swimming is going a lot, lot younger.”

“I felt old at 23, sad to say,” Adlington said at the time.

Now 28, Adlington reflects on her stellar career — four Olympic medals, including two gold, a world title and a world record — and said she peaked both physically and mentally at age 19, the year she won two of the premier races at the 2008 Beijing Games.

She said sprinters might peak later because their events rely more on power and strength, “which often happens early 20s rather than teens.” But she said Ledecky doesn’t fit any mold and might be able to stay in the pool longer, improving her performance even as she ages. “You can’t compare anyone to Katie,” she said.

For Adlington — and so many other swimmers — the rigors of the sport began to catch up to her. Her shoulder began bothering her at age 21, which hampered her performances in the water and her enthusiasm out of it. “Mentally, it was challenging racing the same distances,” she said, “but no fun.”

A previous generation of swimmers adhered to different training philosophies. Ledecky and the younger crop pay more attention to dry land work, stretching and recovery. They don’t swim laps for the sake of swimming laps. The end result for many is preserving their body for a longer career.

“What we did was grueling,” said Brooke Bennett, a three-time Olympic champion who competed at the 1996 and 2000 Summer Games . “But it was what we knew — just hours and hours of training. But I think now with technology, we’re finding ways that we can be smarter. It’s the quality of training, not just the quantity.”

Bennett said she peaked at age 20, winning the 400 and 800 races at the 2000 Olympics. She tried for several years to match her best times, but shoulder injuries hindered her.

“I think to myself all the time, if I was doing the stuff they do today in my late teens, would I have had the same problems with my shoulders? Would I have had different outcomes?” she said. “It’s all stuff that we didn’t know. That’s changing a lot and keeping our swimmers healthier and allowing them to go into the mid-20s or 30s.”

Ledecky has been relatively injury-free for most of her career. Coaches credit her training, technique and attention to detail. And while there’s no foolproof formula for staying healthy, Mark said Ledecky’s technically sound mechanics could decrease her likelihood of injury.

“Not that all injuries are caused by technique,” he said, “but there can be a connection. Your technique, the amount of reps that someone’s going through with their arms, you hope your body can continue to support it all.”

Mark has worked with Ledecky since 2011, dissecting video, helping identify the smallest tweaks that might help her find fractions of a second in the pool. He says she’s like a sponge and is able to quickly embrace and apply any coaching tips.

That drive to improve could be what helps her continue to lower times. She finds areas to hone from one Olympic quad to the next. Following her gold at the London Games, Ledecky improved her breathing mechanics, kept her head lower in the water and improved her dolphin kicks coming off the wall. Her haul from the 2016 Rio Games included four golds and one silver, the most medals any American woman has brought home from an Olympics.

“What drives Katie is not the records, not the medals,” said Bruce Gemmell, who coached Ledecky through the Rio Olympics. “It’s finding ways to get better. She’s brings that in macro sense and a micro sense every day.”

Bennett coaches young swimmers and said that Ledecky and the current generation of female swimmers already have had a huge impact on the sport, potentially opening doors for younger swimmers. In years past, college coaches would scout high school boys, knowing their best years were still ahead of them. But many girls turned in their best times before setting foot on a college campus.

“Looking at somebody like Katie, Lilly King [20 years old], Melanie Margalis [25], these are female athletes that are changing that,” Bennett said. “They’re saying, ‘I was good in high school, but I’m 20, and I’m only getting started.’ That’s huge for girls in our sport.”

USA Swimming aims to keep its top talent in the pool as long as possible, and there’s more money and sponsors than ever before, making it financially worthwhile for sprinters and distance swimmers alike to prolong careers as long as possible.

Ledecky, of course, has passed on endorsement opportunities so she can compete for Stanford. How long she competes won’t likely be dictated by money or perhaps any other external factor. As she has since she burst onto the international stage as a 15-year-old, she’s doing things on her terms.

“I guess eventually there’s a ceiling for all athletes,” Gemmell said. “Katie’s willingness to commit to doing what it takes to do better and not resting on any laurels makes her ceiling higher than so many others and makes it so the trajectory may have or will continue to slow, but to think it’s maxed out would be naive of all of us.”