A Naiad’s Record Achievement

A scene from the film, Nyad, starring Annette Bening.

By Mary Carpenter

Note: This post contains spoilers.

NYAD, the Netflix biopic, portrays swimmer Diana Nyad striving to complete a continuous swim across more than 100 miles of open water (depending on currents, tides, wind, etc.) from Havana to Key West—for which her specialized training and diet regimens can both inspire and inform the recreational swimmer.

And in warm Caribbean waters, temperatures in the 80s are enough lower than the body’s norm to achieve health benefits touted for “cold-water” swims, in water under 57 degrees. And, recently popular, the “ice mile” refers officially to any swim, under supervision, in water below 41 degrees F. wearing only a swim suit, cap and goggles —with medical checks before and after highly recommended.

Especially inspiring for older swimmers, Nyad didn’t begin training for the Cuba-to-Florida challenge until her 60^th birthday — after taking a 30-year break from long-distance swimming. For this nonstop, more than 50-hour swim, however, Nyad’s greatest strength may have been her mind.

“I think it was her belief in herself that she could do this,” Women’s Sports Foundation CEO Kathryn Olson told NBC News. For long swims, Nyad also created mental routines (which included counting to 100 in four languages and an 85-song playlist) that she ran through again and again, hour after hour.

Nyad’s training schedule for the winter and spring before her five Cuba-to-Florida swim attempts that took place in August began with land exercises: 100 burpees a day along with military-style push-ups and Pilates core strengtheners like the “teaser”—making a V-shaped formation with legs and upper body extending upwards in opposite directions.

After January, Nyad began to up her time spent swimming  and trained less on land, although she still biked 100 miles one day a week. For the three or four months before a long swim, explains ESPN’s Natalie MacKenzie, “too much of virtually any form of cardio other than swimming builds the legs too much—counterproductive when you’re trying to be as buoyant as possible over…hours of swimming.”

Even while swimming, those aiming to go a long distance avoid strenuous kicking —though that also helps protect the heart. “Extreme endurance athletes have probably a five- or sixfold increase in the risk of atrial fibrillation,” University of Texas Southwestern Medical Center internist Benjamin Levine told Outside. For swimming—in contrast to ultramarathons that can overstress the joints—said Levine, “It’s the heart that’s going to be the limiting factor.”

Also, a measured slow pace can help keep swimmers’ exertion “completely aerobic,” explained swimmer Ross Edgley, who said the goal is to avoid “tapping into your lactic threshold” —the point when lactic acid starts accumulating in the muscles. Constantly adapting his technique to move with the least possible effort, Edgley notes: “I barely kick my legs at all, and it’s just very much a rotation in the upper body…I’m sort of floating efficiently.”

“Hardening” refers to adaptation both to cold water and to seasickness—with nausea and vomiting the most unpleasant and dangerous issues with long-distance open-water swimming, made worse by constantly swallowing salt water. In a 1979 effort, Nyad lost 29 pounds in less than 42 hours of swimming—with the weight loss, as well as her failure to complete the swim, later blamed on her swim diet: mostly cake and Coke.

“I was vomiting constantly,” Nyad told the Today Show—during the 50-plus hours of her Cuba-to-Florida swims, despite ongoing efforts to improve her nutrition formula. According to ESPN, “what works for a marathon runner or cyclist doesn’t necessarily work” for long-distance swimming, which requires spending dozens of hours in a prone position not ideal for digestion. Along with special liquid formulas to help replace lost fluids and electrolytes, Nyad consumed small banana pieces covered in peanut butter for protein and to help coat and protect her stomach.

During the months of training, Nyad consumed about  9,000 calories on non-swimming days and about 3,500 when swimming: “there simply aren’t enough hours to consume any more than that when you spend half the day in the ocean,” writes MacKenzie. But Nyad has said, “it’s not as fun as it sounds to eat that many calories.”

The warm Caribbean waters added the risk of encountering poisonous marine animals and sharks. Nyad refused to use the shark cage that helped previous swimmers on this route. But along with goggles and a swim cap, she wore a special mask to protect against stinging jellyfish —though it slowed her down by about .3 mph and forced her to swallow more seawater.

Health benefits of swimming include a 41% lower risk of death due to heart disease or stroke than non-swimmers—as well as a 28% lower risk of early death overall, writes Cleveland Clinic exercise physiologist Christopher Travers about a Swim England-commissioned study.  Travers adds that, because swimming creates resistance but with low impact, it’s “one of the best exercise options for anyone with arthritis…helping to reduce symptoms.”

“Swimming makes your body use oxygen more efficiently,” Travers reports, which is related to improvements in lung strength and capacity. For those who prefer to start “small with something like water walking or water aerobics,” he suggests beginning in water up to the waist and walking slowly across the pool, swinging the arms and keeping the back straight and then moving into deeper water.

For swimmers in “very cold” water—below 57 degrees—the benefits accrue for “two of the biggest hallmarks of aging: high blood pressure and arthritis,” Hirofumi Tanaka, director of the University of Texas, Austin, Cardiovascular Aging Research Lab, told Why We Swim author Bonnie Tsui. For ice swimming, because of the hypothermia risk, athletes must be in good health and have trained in cold water —and they swim at high intensity for several minutes.

“We realized the effects of swimming actually surpassed the magnitude of the effects of walking or cycling,” Tanaka said. And for those with arthritis, “cool” water at 80 degrees or lower “stimulated mobility —without pain—and circulation,” and lowered blood pressure more than land-based exercise training.

Critics of the film Nyad point to the swimmer’s habitual revision of her stories over the years along with the inflations of her accomplishments. But for me, the film documents Diana Nyad’s unwavering determination —along with her intensive training and her mastery of the enormous distance of open water and number of hours involved in the swim from Havana to Key West.  Also very impressive to me is the walk to shore following so many hours of swimming: to officially complete an unassisted swim, she had to reach the point where both ankles were out of the water —a long walk in Key West waters that are too shallow to give much support.

—Mary Carpenter regularly reports on topical subjects in health and medicine.