Cancer survivor becomes first to swim Channel four times non-stop, as scientists say being a woman was key to her success

A woman who overcame cancer just last year has become the first person to swim across the English Channel four times without stopping, as scientists say her gender could be key to her success.

Sarah Thomas swam for 54 hours - from England to France, to England, to France and back to England, fighting against strong currents, salt water in her throat and jelly fish stings on her face.

The 37-year-old American completed the epic challenge at 6:30 on Tuesday morning.

Instead of the 80 miles it should have been, Ms Thomas covered nearly 130 miles after tidal pulls took her off course.

She celebrated with champagne and a pack of M&Ms on the beach in Dover.

But this almighty feat was undertaken against the backdrop of a battle with cancer only last year.

“I was officially diagnosed with breast cancer in November,” Ms Thomas told the Financial Times earlier this month.

“This time last year, I couldn’t swim and really wasn’t sure what was possible for my future.”

After receiving radiotherapy treatment she said: “It was too painful to swim through my burns. I blistered and was told it wasn’t safe to swim because of the risk of infection.”

Doctors thought she may never reach an elite level again. Yesterday, she dedicated her record-breaking swim to "all the survivors out there".

Ms Thomas works full time in Denver, Colorado as a healthcare recruiter, but still finds time for 29 hours of swimming a week, covering 68 miles.

Monday to Thursday, it’s usually two-and-a-half hours in the evenings. Friday is a rest day, but the weekend is intense. The hours are ramped up to as many as eight-and-a-half on a Saturday and 10 on a Sunday when she’s training for a challenge.

Fuelling the mission was a special sports drink called CarboPro, designed for endurance athletes and further infused with electrolytes and caffeine.

Legal in professional competition, the makers claim that one serving (50g) mixed with water “represents theoretically as much carbohydrate content as 200g of cooked pasta; or as much as 430g of potatoes.”

Given that Ms Thomas was having one of these every half an hour, that is the equivalent of 46.4kg of potatoes, or 21.6kg of pasta over the course of her swim.

While the caffeine helped to keep Ms Thomas awake, so did natural bodily instinct, according to Eddie Spelling, captain of her support vessel.

“Some swimmers can actually sleep in the water, but Sarah didn’t do that,” he told The Telegraph.

The 67-year-old has been escorting Channel Swimmers for over 10 years on his motor cruiser, Anastasia.

“She is a supreme athlete who goes into a different realm of consciousness when she’s in the water.

“The human body is an incredible physical machine but Sarah had a mental state beyond compare. It is only through sheer bloody-mindedness and determination that she could do what she did,” he added.

Aside from the caffeine, electrolytes, carbohydrates, good weather and patient shipping traffic, Ms Thomas had another advantage: her gender.

Endurance swimming is one of the few elite sports where women are physiologically better suited than men, according to scientists.

Swiss Doctor Beat Knechtle has studied male and female performance in ‘ultra’ events and published papers on the subject.

Looking at 30 years worth of finishing times at the 28.5 mile Manhattan Island Marathon Swim, he found that on average, the best women were 12 to 14 percent faster than the best men.

Speaking to the Financial Times, he said: “Women have an advantage due to their higher body fat, which provides insulation against the cold and better buoyancy.”

Given that wetsuits are banned for official open water attempts, this plays a huge role in long distance swims.

Lynne Cox, who held the record for the fastest Channel swim in the 1970s said: “Thank God (or Ben & Jerry’s) for my body fat,” in her book Swimming to Antarctica.

Speaking to Science of Us, she said: “I think the thing about women’s body fat helps. But besides it being an insulator, you have a different level of flotation in the water, which may change the amount of work you do, so that makes a huge difference in energy expenditure.”

And the results show it.

The four longest distances ever swum in open water, without the assistance of currents have been completed by women. The record of 104.6 miles was set by Ms Thomas in 2017 at Lake Champlain.

The longest current-neutral ocean swim? Another woman, Chloe McCardel a 29-year-old Australian who swam 77.3 miles in 41 hours from South Eleuthera Island to Nassau, Bahamas.

For Ms Thomas, there will be more challenges ahead. But for now, some sleep.