By his own account, three-time Olympic swimmer Chase Kalisz is an old man in a young person’s event, one that’s uniquely arduous. 

As the 30-year-old swimmer looks to defend his 400-meter individual medley Olympic title from the 2021 Tokyo Games, he knows age is not in his favor, especially now in his 11th year competing in arguably the most brutal pool event.

“It's an incredibly tough thing to be doing for that long,” Kalisz said after qualifying in the 400 IM for the Paris Olympics. He’s aiming to be the first man in his 30s to win an Olympic medal in a race that’s at least 400 meters. 

“I definitely didn't foresee myself here where I am.”

The 400 IM requires more physical and mental strategy than just about any other event, with guaranteed, all-encompassing pain waiting at the finish. It’s like four sprint events combined into one merciless race: 100 butterfly, 100 backstroke, 100 breaststroke and 100 freestyle in that order. 

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“That race is very taxing, emotionally and physically, because after the race is just like, ‘Oh my gosh, everything hurts,' " said two-time Olympian Katie Grimes, who’s qualified for the 400 IM in Paris. 

“You don't want to move. You don't want to talk. It's just terrible.”

For Team USA in Paris, Kalisz will be joined by trials champ Carson Foster, 22, in trying to take down world-record holder and 22-year-old Frenchman Léon Marchand — Kalisz’s training partner who broke Michael Phelps’ last standing individual world record in 2023. On the women’s side, it’s 18-year-old Grimes and 22-year-old Emma Weyant. 

The men’s 400 IM is July 28, followed by the women’s July 29.

Overcoming the mental and physical challenges of the 400 IM comes with training. Maintaining focus while doing 100s of all four strokes as your muscles are increasingly burning “is a pretty daunting task,” said Kalisz, who trains with Longhorn Aquatics under Phelps’ longtime coach, Bob Bowman. 

“There’s no way to hide in that race,” Phelps noted in 2016 ahead of the Rio Games.

“Pain is inevitable,” Kalisz added.

Pace work in practice helps with the mental and physical hurdles, he said. For example, he’ll swim a difficult main set and then transition to pace work, mimicking the race itself “when you're feeling the effects of being broken down and tired.” 

But in what Grimes described as “a full-body race,” crafting a strong strategy mitigates some of the formidable elements. 

“It's like you're watching a bunch of different races because everyone has different strengths and weaknesses,” she said.

A “terrible” breaststroker like Grimes has confidence in her butterfly and backstroke legs but can’t exactly relax. She focuses on building as much of a lead as possible, knowing some of her competitors will catch her on breaststroke before the all-out 100 free to close.

For Kalisz, breaststroke is where he excels. He said early in his career, he would burn his lower body on butterfly and backstroke and have little left for breaststroke, the only stroke driven by your legs. But after training with Phelps, he said he learned to float his legs more and save them for his surge in breaststroke.

At the Olympics, when best times take a backseat to the podium, Kalisz is also aware of how his competitors swim their races and where he needs to be in comparison going into the breaststroke leg. He said he lets them do all the thinking in the first half before making his move in the second. 

“There's a lot of lead changes that usually happen in the 400 IM, and that's why I think it's the most beautiful race,” Kalisz said. “I think it's absolutely a beast of a race, but the mental aspect of it is also pretty brutal itself too.”

For first-time Olympian Foster, the first thing that would go wrong in his past 400 IMs was losing focus as he’d “battle those inner negative voices.” But he said working with a mental performance coach the last three years has helped him regain control and close with a strong freestyle leg.

Also qualified for Paris in the 200-meter IM, Foster said the shorter medley hurts more but for a shorter period of time, whereas the “grueling” 400 IM hurts for the whole second 200.

“I gotta get to that dark place,” Kalisz said. “That five minutes that you're in the ready room before thinking about it and knowing what’s about to come — it could be a good race, it could be a bad race, but it’s going to hurt no matter what.”