Taking a dip in a freezing lake or an ice bath is a growing trend, with practitioners claiming a variety of health benefits. So, what happens to your body—and your mind—when you’re immersed in cold water?
I’m standing on the lake edge in my swimming togs. The waves crash, and there are white caps further out. There’s the threat of rain, with heavy clouds obscuring the mountains. Goosebumps have popped up all over my exposed skin, and the hair on my arms is standing up—my skin mounting a pathetic attempt to keep me warm.
As I go, I test my footing on the slippery stones—in front of me are a couple of large, submerged rocks that I don’t want to stumble over. I have to walk out at least 50 metres before the lake is deep enough for me to duck down. My lungs instantly contract, then the hyperventilating starts. Violent, full-body blasts, like a blacksmith’s bellows. My heart races.
This is “cold shock”, my nervous system’s reaction to the 9°C water. I tell myself that it will pass after a minute or so. It doesn’t help. I can’t help remembering that around 20 per cent of people who fall into cold water die in the first two minutes. One involuntary gasp—it only takes a small amount of water to be inhaled into your lungs for you to drown. This is why I don’t go in any deeper than my shoulders.
I can hear the whooshing of my breath above the waves, some of which break over my head. That dreaded ice-cream headache. My heart races. All I want to do is flee. All my normal coping mechanisms have been overwhelmed—I’m on the verge of panicking. A brief surge of beta-endorphin hormones in my brain tries to reduce the pain from the needles of cold driving into my chest. I know that cortisol, the stress hormone, is being excreted in the middle of my tongue. My body is basically producing its own little medical lab, and I’m getting a mainlined hit. I wonder, not for the first time: Why do people do this on purpose?
There’s one reason I don’t bolt out of Lake Wakatipu right now: Laura Warren, who makes a living teaching people how to put up with cold water. She holds my shoulders and tells me to hold hers, and that’s all it takes to bring my breathing back into focus. That physical connection is what keeps me there.
The sensations change. After about a minute, my breathing is almost normal. I begin to feel calm, an overwhelming sense of well-being. For two more minutes, I breathe. I become part of nature—not an innocent bystander, always trying to insulate myself from it with heaters, puffer jackets, fire. I wish this euphoric feeling would stick around, but the moment has passed, and the cold is starting to seep in.
I start to shiver—my body’s last defence against the chill. The veins in my extremities have begun to constrict, so I’m losing the ability to control my hands and the muscles in my arms—it’s because they have a high surface-to-mass ratio. I know that if my core temperature drops only a couple of degrees from 37ºC, I’ll become mildly hypothermic. We get out of the lake long before that can happen.
I stand on the shore for a few minutes, savouring the calm. The wet stones at my feet glisten like jewels, the clouds look like they’ve been manipulated in Photoshop. I can see every contrasting grey. My back is hot, a strange sensation. Then the shivering begins in earnest, and I hurry to get dry. It’s hard to sip a hot chocolate with shaking hands.
All up, I spent three minutes in the lake. I know what took place within my body during that time. But what happens to it after I get out? How does this immersion therapy change me long term?
According to Warren, I’d have to make it a habit to find out.
“You can’t expect to feel the full benefits after only one or two attempts,” she says. “You need to commit.”
Cold-water immersion has long been a therapeutic practice in northern hemisphere countries such as Finland, Poland and Norway—one religious holiday in Russia even involves an ice bath. But, ever since the Dutch motivational speaker and extreme athlete Wim “The Iceman” Hof began to advocate cold therapy in the early 2010s, freezing the balls off a brass monkey has had a trendy new following. The Wim Hof Method advocates regularly practising cold exposure, as well as Hof’s breathing technique, and practitioners associate the method with a turnaround in their physical and mental health. Anecdotes abound from “Hoffers” who say the method helps with medical conditions as diverse as migraines, Parkinson’s, ulcerative colitis and multiple sclerosis. (Research hasn’t been conducted into the method’s benefits on these specific conditions.)
Tom Finden tells me that before he started the Wim Hof Method, he felt “stuck in a rut” and “was just going through the motions”. When I meet him at a cafe across the road from Lake Wānaka, he’s lightly clad while most people have jackets on. He wears a black beanie and shivers slightly. Over the winter of 2021, he ran an event called 10 Weeks Cold Cheeks in which he and around six others met for a series of early-morning midwinter dips in Lake Wānaka.
“Now I’ve got more energy through the day,” he says. “I pay more attention to how I’m feeling. After a session in the lake, my focus is razor sharp.”
Cold therapy is a way to practise tolerating the unpleasant parts of life, says Warren, who is a licensed instructor of the Wim Hof Method—a physical act that reinforces a mental one. Accept discomfort, she says, and it fades. “Cold is just an experience. It’s a felt sense. If you don’t label it, and just observe what’s going on without judgement, it will pass.”
Followers of the Wim Hof Method have given their leader guru status, often citing his 21 Guinness World Records in feats of thermoregulation. Hof nearly reached the summit of Mount Kilimanjaro in shorts, and attempted the same on Mount Everest—but shirtless, too. Mark Woodward, a New Zealand mountaineer and guide who has climbed Mount Everest ten times, remembers meeting Hof at around 7000 metres at the North Col in 2007.
“It was a nice, sunny, warm day, but I didn’t expect to come across a guy wearing shorts,” says Woodward. “He was all bare-chested, strutting around. He was wearing double-insulated mountaineering boots and his shorts were quite long and looked to be down-filled. I’d seen him at base camp and heard of his bold claim but just dismissed him as being another one of the wack-jobs that you get on Everest. We were passing on the fixed lines and stopped for a chat. I said to him, ‘So you want to be the first person to climb Everest in shorts?’ He replied ‘Yes, yes, no one has done it yet’.”
Woodward, in that cheeky give-someone-a-Kiwi-hard-time way, said to Hof, “Do you realise it’s already been done? Last year, in fact.”
“No, no, no, it hasn’t,” Hof replied.
“Yes, it has. I was the guide on the Mark Inglis expedition—the first double amputee to climb Everest—and because he didn’t need insulation on his lower legs, he had his insulated suit custom-made to end above the knees. They looked like shorts.”
Hof reached 7200 metres before turning back, 1600 metres short of the summit. His willpower isn’t in question. But do his health claims stack up?
Research into the benefits of cold-water immersion ranges from patchy to non-existent. Ice baths have long been used by athletes to reduce muscle inflammation, but studies conflict as to whether this improves athletic performance in the long run. One theory holds that inflammation is a helpful signal of body condition, and turning down its noise has ill effects. When ice baths are tested against other recovery treatments, some studies find that placebo therapies work for athletes as well as, or better than, cold immersion.
Some of Hof’s claims are solid, says Jim Cotter, an associate professor at the University of Otago who studies exercise and environmental physiology. Regular immersion in cold water does lead to physiological changes in the body, meaning that it’s possible to train your body to tolerate the cold better. Substantial cold exposure over two to four weeks, says Cotter, causes the body to convert one type of fat, white adipose tissue, to another type, brown adipose tissue, which helps with thermoregulation. Humans and animals with higher levels of brown adipose tissue take longer to start shivering. “This would probably be helpful if you were a university student studying in a cold Dunedin flat,” suggests Cotter.
An emerging body of research is looking into whether cold-water immersion has mental health benefits. A case report published in the British Medical Journal in 2018 followed a 24-year-old woman who had suffered major depression since she was 17 as she undertook regular cold-water swimming. Cold exposure, the study found, “led to an immediate improvement in mood following each swim and sustained and gradual reduction in symptoms of depression, and consequently a reduction in, and then cessation of, medication”. (A follow-up a year later found she was doing well.)
Cotter is quick to note that a one-person case report is an invitation to further research, not the final word on the matter. And that research is only just beginning. In the United Kingdom, environmental physiologist Mike Tipton, a professor at the University of Portsmouth, is looking at whether adjusting to the stress of cold shock helps people to adjust to broader life stressors.
A small study by Tipton’s colleague, senior lecturer Heather Massey, found that cold-adapted people were less physically stressed by a high-altitude environment than people who hadn’t practised cold immersion. Tipton wants to know: can that adaptation cross over to forms of psychological
AUT University professor of public health Grant Schofield is particularly interested in how cold-water immersion might help people to manage anxiety. Anxiety is an automatic nervous-system response to a perceived threat—just like cold shock.
“Can you get yourself in situations that allow you to learn how to control that nervous system?” asked Schofield in an interview with RNZ. “I think cold water, and breathing, is such a great way to do that because it does induce some anxiety, but it’s not dangerous, and it’s certainly a situation that you can gently learn to overcome.”
Cold-water immersion, in other words, is a way of practising being stressed—of finding mental techniques, such as slow breathing, to blunt the edges of a stress response.
When you feel like you don’t have any control over your life, pushing the boundaries of what you find comfortable lets you claw some of that control back. It’s “safe jeopardy”, says Laura Warren, the Wim Hof Method instructor. Extreme experiences give us a reference point in which to navigate difficult and stressful times. It’s a bit like having a life GPS with waypoints to follow. Ease your way into the cold, take small steps, frame it as something you want to do. Like other outdoor activities, cold exposure can become a metaphor for staying the course and overcoming difficulty.
Warren admits “the cold is not for everyone”, and for some people who get into cold water, it’s their first and last time.
That might include me. I’m not planning to make a habit of cold immersion, but I expect my experience with Warren has probably helped me with my fear of cold water. As a kid, I came close to drowning when a Lilo I was floating on in Lake Wānaka sprang a leak and cold shock caused me to inhale water. Faced with cold-water immersion by accident in the mountains, or falling out of a kayak in the lake, perhaps I’ll be better equipped to survive the shock.
On the other hand, Schofield is now a daily cold-water swimmer after trying it out over the first COVID-19 lockdown and reluctantly noticing its benefits. “I didn’t even want it to be true,” he says, “because I look at cold water and go, ‘Oh, my lord, are you kidding me?’”
One of the biggest issues with the Wim Hof Method, says Jim Cotter, is the way that Hof talks about it. Hof’s language and level of certainty have more in common with conspiracy theorists than scientists. Hof regularly references “proof” that following his method improves people’s immune systems, helps them to lose weight and reduces stress.
“Proof implies there is no room for error,” says Cotter. “Quite simply, that doesn’t exist in the real world. In science you don’t have proof. You just accumulate evidence towards something until new evidence comes along to make it implausible.”
Cotter is frustrated that dramatic, concrete, certain statements travel so much faster—and further—than the complexities of reality. “You want to say you’ve proven something beyond any doubt,” he says. The temptation is there. It sounds so much better. “It’s a real dilemma in today’s science.”
Still, Cotter thinks there’s much to be learned about the benefits—and risks—of breathwork and cold-water immersion. “It’s early days,” he says, “so watch this space.”