How to Swim for 67 Hours Straight

It was Aug. 7 when Sarah Thomas, 35, of Conifer, Colorado, calmly walked down a slick, concrete boat ramp at Rouse's Point -- the last stop in the United States at the northern end of Lake Champlain on the New York and Vermont borders. She was ready for the daunting challenge that lay ahead. The accomplished marathon swimmer was beginning a journey that would take her a little over 52 miles south to Gardiner Island and then back to her starting point: all at once, without stopping, without sleep, without a wetsuit and without touching another person or her support boat the entire time. She achieved this 104.6-mile swim -- dubbed a "century swim" because it was over 100 miles -- in 67 hours and 16 minutes to notch a new world record for longest current-neutral swim. (Current-neutral means she didn't have assistance from currents in the water.)

But it took much more than the nearly three days she spent in the 72-degree lake water to reach this goal. Thomas grew up a swimmer and swam on the varsity team at the University of Connecticut. After graduation, she moved to the Denver area and swam at a local pool for fitness. When a friend suggested she try a 10-kilometer event in the Horsetooth Reservoir in Fort Collins in 2007, she wasn't sure she'd be able to finish what sounded like a staggeringly long distance to swim. But not only did she finish, she found her calling as a marathon swimmer.

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A marathon swim is any swim event 10 kilometers (6.2 miles) or longer. The most iconic example is a solo swim across the 21-mile English Channel, so Thomas finished the equivalent of nearly five English Channel swims. There are lots of other marathon swims around and a growing community of marathon swimmers trying to complete them. Although the water in Lake Champlain was about 10 degrees warmer than the 62-degree water found in the channel for the average swim, fresh water feels a couple degrees colder than salt water at the same temperature.

Thomas, who works full time as a recruiter for HealthSouth, a network of rehabilitation hospitals based in Birmingham, Alabama, got hooked on marathon swimming and built up to longer distances over time by following a common approach to endurance sports training. Christina Buchanan, professor and director of the high-altitude physiology master's program at Western State Colorado University, says this progressive adaptation approach to training is common in long-distance running, cycling, triathlon and any other sport where competitors need to just keep going. "The idea is that you're overloading your body by doing more than you did before. So if you can swim three miles today, tomorrow you would swim four. You stress your body in such a way that in the recovery phase, it makes you ultimately stronger."

Buchanan says these adaptations occur during cyclical rest periods that essentially give the body a chance to rebuild from the stresses of training. For many long-distance athletes, the training cycle begins a few months before a focal competition with laying a "base" -- training for progressively longer distances. A subsequent phase may also include focused speed work to increase pace and technique practice to refine the mechanics required to swim or run more efficiently. Lastly, a shorter period of rest, called a "taper," in the last few days or weeks leading up to the focal event gives competitors time to recover and fine-tune themselves so they're as ready as they can be on race day.

In Thomas' case, she has a lifetime of base in that she's been a swimmer for 30 years and has 10 years' experience training for marathon distances. But for this particular event, she says she launched her training in January by establishing a consistent swimming routine. (She had taken about three months off any heavy training after completing an 80-mile swim across Lake Powell in Utah and Arizona in October 2016.) From there, she slowly built up through the late winter and into the spring, eventually peaking at about 30 hours per week of swimming (covering roughly 55 to 60 miles each week) for a full two months in June and July before backing off the distance about two weeks prior to her August 7 swim date.

Thomas says her training worked perfectly, and Buchanan says the gains she experienced occur at the cellular level in the muscular system, the nervous system, the cardiovascular system and even in the way the body moves oxygen to working muscles. "You increase the number of capillaries so you can deliver more blood and oxygen to working muscles. Your cells create more mitochondria," the cell's energy production centers.

Some athletes train at altitude, as the body must make similar adaptations to cope with the thinner air and less oxygen that's found at higher elevations. Thomas lives and trains year-round at nearly 10,000 feet up in the mountains outside Denver, which Buchanan says is likely a benefit when Thomas comes down to sea level to compete. (The surface elevation on Lake Champlain is less than 100 feet above sea level.)

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In addition to the training adaptations Thomas has accumulated through years of swimming ever longer distances, her own innate physiology likely plays a role. "From a genetic perspective, she probably has a good cardiovascular and metabolic system that are probably primed to do this sort of thing," Buchanan says, noting that genetics is often a differentiating factor in athletic performance. "It's why some people are Olympic athletes and others aren't, even if all other factors are the same." Although she's the only ultra-endurance athlete in her family, it seems Thomas has found the sport she's genetically best designed for.

Nutrition and fueling the swim was also an important component of her success. During the swim, Thomas would pause every 30 minutes to "feed" on a range of items, including a carbohydrate drink, electrolytes and a little bit of caffeine later in the swim to help offset sleepiness. She had a protein recovery drink every few hours and occassionally ate some warm risotto. She's refined this diet over the years and says the risotto was a recent addition that was so helpful during her Lake Powell swim that she won't ever do another event without it.

Having an efficient stroke technique that fits her individual physiology is also part of why she was able to complete hundreds of thousands of arm rotations without injury. Evan Morrison, co-founder of the Marathon Swimmers Federation and the lead observer on the Lake Champlain century swim, says Thomas' technique was remarkably consistent for the duration and is seemingly purpose-built for ultra-long-distance swimming. "She has a compact, relaxed, balanced stroke that minimizes the stress on her shoulders, even over long durations. She maintains a flat, hydrodynamic body position that minimizes drag, even when she's exhausted."

Shortly after completing the swim, Thomas remarked that she was glad to be finished, but that she could have continued swimming if she needed to. She says she never felt too fatigued or sore in her muscles to continue, which she chalks up to having trained appropriately. However, she did concede that she was tired and wasn't sure she'd be able to stay awake much longer. Morrison says, "I think 67 hours is probably already pushing the limits of how long a person can stay awake while swimming and still making any forward progress.... At some point you have to sleep, right?"

For whatever reason, Thomas seems better at tolerating sleep deprivation than a lot of other people. She finished the swim a little before 4 a.m. on Thursday, August 10 and within an hour or two was in a hotel bed sleeping deeply for about six hours. She got up, ate, traveled to meet her crew -- the group of 10 friends and family members who had supported her on the journey from the support boat -- and then went back to bed about eight hours later. In the month since the swim, she says she's felt a little more tired than usual, but not as much as she expected she would, and she was back in her home lake swimming lightly within a week of completing the Lake Champlain event. Her recovery has been relatively easy, likely due to a combination of smart training and good genes.

In addition to all these factors, an even bigger component of her success is probably all in her head. Despite the variable weather she experienced -- chilly rain for much of the first day, breezy sunshine on the second day, blustery 20-mile-per-hour winds overnight into the third day -- Thomas didn't let any external forces divert her focus. "This swim was about 90 percent mental, 10 percent physical," Thomas says, meaning that maintaining the right frame of mind throughout the event accounted for the vast majority of her ability to complete it. Unlike during her Lake Powell swim where she says she experienced a "mental breakdown" about 30 hours in and nearly quit, she never felt like she couldn't keep going in Lake Champlain. Jennifer Dutton, a Massachusetts-based swimming coach and marathon swimmer, says the mental side of things can't be overstated. "Sarah has learned to program her brain to keep it in the right place. She doesn't let her emotions interfere." What's more, "every time she trains and every time she does a big swim, she knows she can maybe go a little farther. She assimilates every success and recognizes that she can push that limit more. She's willing to explore that discomfort," at the fringes of capacity. "Most people will avoid that, but she goes toward it to seek her limits," Dutton says.

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If you're aiming for something big of your own, whether it's a one-mile ocean swim, a 5K road race, your first triathlon or a marathon, be sure to build up progressively and allow your body time to adapt to what you're asking of it. "Start with a small, realistic goal and build your confidence," Dutton says. Working with a coach can be a good place to start, particularly with a technique-heavy sport like swimming. "And be sure you understand whether your goal is just to finish the event or to win." If you build up safely and progressively, you may surprise yourself with what you can achieve.

Lastly, in all this striving, don't forget to enjoy the journey. "It's so amazing to test your limits," Dutton says.

Elaine K. Howley is a freelance Health reporter at U.S. News. An award-winning writer specializing in health, fitness, sports and history, her work has appeared in numerous print and online publications, including AARP.org, espnW, SWIMMER magazine and Atlas Obscura. She's also a world-record holding marathon swimmer with a passion for animals and beer. Contact her via her website: elainekhowley.com.