Could pool at Paris Olympics be a factor in slower swimming times?

(NEW YORK) — Three former world record holders, Australia’s Ariarne Titmus, USA’s Katie Ledecky, and Canada’s Summer McIntosh fell well short of their best times in the women’s 400 freestyle event at the 2024 Paris Olympics on Saturday.

In contrast, none of the eight swimmers in the men’s competition on Sunday would have finished better than eighth at the 2021 Tokyo Olympics.

World-class swimmers rarely get slower in their prime and technology constantly improves, so why aren’t we seeing records drop like usual? Can a pool really be responsible for slowing down the swimmers?

Jud Ready, a professor at Georgia Tech’s School of Material Science and Engineering, teaches a class on engineering in sports and says a pool can be slow. He spoke with ABC News’ “Start Here” about the difference in this 2024 Olympics pool compared to others.

Ready and his alma mater, Georgia Tech, know about pools. The school hosted swimming competitions in the Atlanta 1996 Games and still boasts the so-called “fastest pool in the country.”

So what makes a pool fast? According to Ready, pool engineers obsess over keeping the water calm.

“You want to not have the other swimmers impact each other,” Ready said. “So any sort of waves or wake or splashing or anything like that, you want that to not impact the body next to you.”

When you’re dog paddling, a few splashes might not make a big difference. However, elite swimmers create waves when they thrash. Some swimmers describe riding the wake of others around them. Some of those waves travel downward, and as they bounce back up, it’s like swimming through ever-so-choppy water.

And the depth of the pool plays a critical role, Ready says.

Well, it turns out that the pool in Paris isn’t very deep. The tiles on the bottom are about 2.2 meters underwater, which is about 7 feet deep. Which is not very deep, according to Ready.

According to World Aquatics, the minimum depth for long swimming must be 2 meters (6.5 feet), but a recommended depth of three meters (9.8 feet) is advised to provide the best environment.

While some experts say 3 meters is the best, others say 2.5 is ideal. But none suggest 2.2 meters.

“And if the pool is deep enough, it’s two and a half,” Ready said. “Somebody has done some calculations to determine that two and a half seems to be a magic number where that energy [of thrashing] has dissipated.”

The differences are slight, but they could explain the slightly slower times in the Paris pool. Other factors at play in pool design include gutters to keep water from ricocheting off the sides, lane dividers to dampen the effect from your neighbors, and jets that affect water movement.

“If we were to do that in an Olympic-sized pool, the current to recirculate many hundreds of thousands of gallons of water per hour would create either a current favoring you in one direction or opposing you in another direction,” Ready said.

Ready says modern pools recirculate water from the bottom, pushing swimmers upward. He also mentions that world records were once influenced by full-body swimsuits that made swimmers more buoyant and streamlined, but these swimsuits are now banned at the Olympics, much to his disappointment.

“I want materials to make everything better,” Ready said. “We’ve got technology to make better swimsuits. But some (have) there’s opposition to that. And I’m like, well, let’s go back to swimming in wool swimsuits then, if you’re worried about that.”

The International Olympic Committee (IOC) has not yet responded to ABC News’ request for comment.

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