Superhuman: The secrets of the ice man

• 24 February 2009 by Duncan Graham-Rowe

PERCHED on the edge of an Antarctic ice sheet, Lewis Gordon Pugh surveys the waves. At 0 °C, water does not get much colder than the sea beneath him. Undeterred, Pugh unzips his jacket, strips down to his swimming trunks and dives in.

Most of us would start to hyperventilate uncontrollably if we dived into such cold water. Pugh doesn't even gasp in pain but instead starts swimming. In December 2005, when Pugh took this plunge (pictured above), he went on to swim a kilometre in just over 18 minutes. Many ordinary people would drown after just a few minutes in such cold water. Pugh, however, not only survived but went on to make several more long-distance swims in extremely cold water (see graph). So what makes him able to keep swimming in such extreme cold?

A study of Pugh published last month has confirmed that his response to cold water is anything but normal. Remarkably, though, while Pugh may have some innate advantages, it seems his near-superhuman ability is largely down to training - so perhaps it could be something we are all able to learn.

High metabolism

Pugh is far from the first to swim in icy water. There is a long tradition in Russia, China and many northern European countries of carving holes in frozen lakes, rivers or sea ice and diving in, often as part of a cultural or religious ritual. These are normally just quick dips, though: rarely do they involve distance swimming. Japanese and Korean pearl divers used to swim without wetsuits in temperatures of around 10 °C for up to 30 minutes. Part of their secret is their metabolism: the colder the water that Japanese Ama divers swim in during winter months, the higher their resting metabolic rate.

Even so, studies of Japanese Ama divers who have been diving for many years show that their response is not that different from the rest of us. Their core body temperature drops to 35 °C after 30 minutes in cold water - just above hypothermia, the point beyond which the body cannot warm up again without help. In contrast, Pugh can keep his core temperature as high as 36 °C even after swimming for 30 minutes in much colder water. How does he do it?

His background seems ordinary enough. Born in 1970 near Plymouth, in south-west England, he went to boarding school at the age of six. It wasn't until later, when he moved to South Africa, that he fell in love with swimming. At the age of 17, one month after his first proper swimming lesson, Pugh took part in an organised 7-kilometre swim from Robben Island - where Nelson Mandela was held for 18 years and the water is a chilly 12 °C. Back then he wore a wetsuit, but he says the swim planted the seeds of a passion for long-distance swimming and a desire to set new records.

Mental preparation

Over the past 20 years he has taken part in 17 long-distance swims, including across the English Channel, along the whole of the river Thames from Kemble to London, and a 204-kilometre, 21-day swim along Sognefjord in Norway. During his travels he began noticing the effects of climate change such as melting ice caps and retreating glaciers, and decided to use his ever more extreme swims to raise awareness of the state of the planet - culminating in two long swims in the Antarctic and the Arctic.

It takes more than ideological conviction to survive icy waters, though. Pugh attributes his success to intense mental preparation. In the weeks building up to a swim he will spend up to 4 hours a day with a coach, going through mental exercises to calm him and focus his mind on the task. These include concentrating on emotionally challenging periods of his life to build up a sense of determination that will help him succeed. "I think about every part of the swim, how it will occur from beginning to end. I hear the sound of my stroke in the water and I feel ice on my skin," he adds.

As the swim gets closer, he psychs himself up by listening to music by the likes of Eminem and P. Diddy. In the minutes before entering the water, Pugh recalls these emotions and is able to raise his core temperature, without doing any physical exercise, to 38.4 °C. That's an extraordinary 1.4 °C above his normal body temperature. Such "anticipatory thermogenesis" has been observed before, but not to such a high degree, says Timothy Noakes, a sports scientist at the University of Cape Town, South Africa, who has been studying Pugh as he swims.

Feeling the cold

Adrenalin

Other experiments found that injections of adrenalin (epinephrine) can induce this effect in Russian cold-water swimmers. Noakes speculates that Pugh may somehow be tapping into this mechanism during his pre-swim preparations.

Pugh has a number of other surprising skills. For example, instead of gradually lowering himself into the cold water, he dives straight in, which in most people would induce a cold shock response, the most common cause of death in icy waters, says Michael Tipton, a physiology researcher at the University of Portsmouth, UK.

Usually when nerves on the surface of the skin sense a sudden and massive drop in temperature, they trigger uncontrollable and involuntary hyperventilation. Swallow water during this stage and you can quickly drown. The blood vessels to extremities also narrow to reduce the flow of blood - and heat - away from vital organs. The sudden rise in blood pressure can trigger a heart attack.

Cold shock response

It is possible to become habituated to the cold so the initial cold shock response doesn't kick in quite so dramatically. But Pugh seems remarkably resistant, although even he does find breathing difficult for the first few minutes. "I certainly feel the cold," he says, "It's excruciatingly painful."

People who survive the initial shock of entering very cold water face another problem: as your limbs and muscles cool, the nerves are affected, which makes coordinated movements such as swimming harder and harder. Pugh, however, seems able to cut the supply of blood to superficial muscles while keeping the deeper ones warm, an ability also seen in the Ama divers.

Pugh does have one skill that has so far defied scientific explanation: when swimming he can stop himself shivering. Normally, shivering is an involuntary response to cold that kicks in once core body temperature drops below 36.6 °C or when skin temperature falls below 28 °C. This is ususally beneficial, as the muscle contractions generate heat, but in cold water it only serves to increase the rate at which the body cools, Noakes says. That's because the increased blood flow transfers more heat from the core to the body's extremities. Somehow Pugh manages to avoid shivering even when his core temperature is below 36.6 °C and his skin temperature is around 5 °C.

Feats of endurance

Close to disaster

Even Pugh has his limits, though. He came close to disaster during a swim across Whaler's Bay off Deception Island in Antarctica. Thirty minutes into the swim, his core temperature started to drop rapidly. By the time he left the water a few minutes later it had plunged to a dangerous 33.6 °C. "If he swam for another 2 or 3 minutes his temperature would have dropped much further and he would have probably lost consciousness," Noakes says.

Undeterred Pugh went on to complete several more ice swims. In 2007 he swam 1 kilometre in the coldest water yet - a glacial -1.7 °C - at the geographic North Pole.

"When I went below 0 °C the cells in my fingers started to freeze. It took another four months before I could feel my hands again," he says. After reaching his goal of swimming both in the Arctic and in Antarctica, Pugh has for now hung up his towel.

The cells in my fingers started to freeze. It was four months before I could feel my hands again

Duncan Graham-Rowe is a freelance writer based in Brighton, UK