The science behind the swimmer: How the dolphin kick is pushing Maggie Mac Neil to Olympic greatness

Also the reigning Olympic champion in 100-metre butterfly, one of a handful to break the 56-second barrier in the event, and a double short-course world-record holder. She came home from the Tokyo Olympics with a medal of every colour and has 28 other world and multi-sport Games medals.

Why did she leave so much out? “It’s how I was raised,” she said with a shrug.

She may be humble about her achievements heading into the Paris Olympics, but that hasn’t stopped the 24-year-old from London, Ont. from setting a history-making goal.  

“No one has repeated as Olympic champion in (women’s) 100 fly, so obviously that’s on my mind,” Mac Neil said. “Going into Tokyo with all the (COVID-19) restrictions and everything, I didn’t really have any goals for myself. It was just a miracle that it was even happening; it’s going to be different this time.”

Managing the mental game — the pressure of the moment, not overthinking things — is as important for success as what happens in the water and, in Mac Neil’s case, under it.

That’s where the fifth stroke happens: the underwater dolphin kick. And it’s where Mac Neil has a biomechanical advantage. 

Her event on the opening weekend in Paris (heats and semifinals next Saturday, final Sunday) is likely to be a Tokyo Olympics rematch and then some. Five of the seven fastest women in history are expected to compete, including American Gretchen Walsh, who lowered the world record at the U.S. trials in June. 

When Mac Neil dives in, she’ll dolphin kick to the allowable 15-metre mark before popping up in a dramatic butterfly stroke. The undulating, full-body dolphin kick is fast — so fast that World Aquatics, swimming’s governing body, enforces limits to stop every race from becoming an exercise in underwater endurance.

Gary Hall Sr., technical director and head coach at The Race Club in California, uses velocity meters and underwater cameras to measure dolphin kick-speed and how body mechanics and positioning affect a swimmer’s acceleration and propulsion, as well as the flip side: deceleration and drag.

Mac Neil is the best he’s ever tested in 11 of the 17 metrics, and in some cases the best by far.

She’s five-foot-five, so that extraordinary speed doesn’t come from a big, powerful frame, particularly long limbs or large feet and hands. It’s her body positioning that reduces aerodynamic drag, the incredible speed of her kicks (one every 0.38 seconds) and the ability to hold speed through technique, according to Race Club data.

For example, because of the way she angles and positions her knees, Mac Neil loses only nine per cent of her speed before her legs whip down on the dolphin kick, whereas others lose 30 to 40 per cent on average.

Mac Neil finished a master’s degree in science of sports management at Louisiana State University in May, a week before qualifying for Paris at the Olympic trials in Toronto, and plans to go to law school. She’s analytical, good with data, and said it was nice to see her underwater ability — considered a strength since her earliest days of competitive swimming — measured and quantified.

The data also dangled the possibility of getting even better with tweaks to her upward kick and timing of her arms. But to Mac Neil, that’s not without risk. 

“If you’re going to take something and make it faster, you’re going to make something slower; it’s a give and take with propulsion versus drag,” she said. “Is it worth trying to change something that I’ve been doing forever and I’m really good at?”

Rick Bishop started coaching Mac Neil at the University of Michigan in 2018. After he moved on to become head coach at LSU in 2021, Mac Neil transferred there to close out a record-setting collegiate career and do her master’s.

“She has natural abilities that I’ve never seen in another athlete — her movement through the water, just her sense of feel for it,” Bishop said.

It’s an edge for Paris, but just one piece of the puzzle.

Rivals including China’s Zhang Yufei and American Torri Huske go out  faster than Mac Neil  on the first lap. Her strength is the second half. In Tokyo, she was seventh at the first wall and pulled herself to gold.

As impressive as that was to watch, Bishop wants Mac Neil to leave a smaller gap to close in Paris. She’s been building leg strength and training specifically to feel more comfortable with a faster early pace.

It worked at the 2023 world championships, sort of. Mac Neil touched the first wall in third place, then popped up from the turn and underwater kicks in first. Uncharacteristically, she couldn’t hold on in the last 20 metres. Zhang passed her for gold, Mac Neil took silver and Huske bronze. 

“As I told Maggie: my bad,” Bishop said. “We probably didn’t do enough rest. Going into Paris, there is no way that we’re not going to be rested enough. I said: I promise you, I’ve learned that lesson, we’re only going to make mistakes once.”

For elite athletes and coaches, stepping back from training is one of the hardest things to do.

“To rest, you have to have courage to rest. You have to believe that everything’s there,” he said.

To make that first lap a fraction easier, Mac Neil has been working on a “less splashy” entry dive. The amount of her body that hits the water dictates the splash and drag. If she can glide through a smaller hole in the surface, she’ll carry more speed from the dive into her first lap. Bishop is also looking for Mac Neil to push her underwater distance right up to the maximum (“exactly 15 metres”) off the dive and turn.

“There was a time when she was worried about it, and she was at 13.8 or 14 metres,” Bishop said. “I’m like: No, more. Let’s take our advantage and maximize it.”

That can be nerve-wracking, because exceeding the limit means disqualification.

Routinely, Mac Neil surfaces after 10 underwater kicks off the dive and 12 off the turn. As her legs get stronger from training, that could change. And day by day, how she feels changes. When she’s deep in a training block, she’s tired, so those kicks don’t have the same power as they will on race day after tapering to peak for the Olympics.

“She’s such a good kicker, if she’s not conscious of it she’ll blow through (15 metres) and there’s  zero forgiveness,” Bishop said. “If you’re beyond in warm-up in a practice suit then you better take two kicks off once you put on that tech suit or you’re playing with fire.”

For all the attention to that underwater skill, Mac Neil gives herself little credit for the hard work — calling it 75 per cent  natural ability and 25 per cent  training. Not so, say multiple coaches who have worked with her. They flip that equation.

“It’s something she’s exceptional at. But the more you work on it, the better you get — and she trains it, hard,” Bishop said.

“There’s so much in competing at this level. The physicality is one thing, but it’s the mentality. When you can sit down at a small dinner table, literally, with the number of people in the world that have beaten you — it’s like three or four people from the last three or four years and that’s it — that gets into your head.”

Mac Neil knows all about the weight of expectations and pressure. A year after the 2021 Olympics in Tokyo, she took a mental health break from the 100 fly. She came back happier and focused on the one thing left to achieve in swimming: winning again.

She’s talked for years about the chance to become the first swimmer to repeat as Olympic champion in her event. Now that Paris is around the corner, she’s also trying not to think too much about it.

“When I’m not overstressed or overthinking things, I tend to do better,” she said.