Challenging your body in crisp temperatures has become routine for the health-conscious – but there are risks. Photo / 123RF
A plunge into freezing water is often billed as a boost for mental and physical health. But the dangers can far outweigh any benefits.
Ice baths, cold showers, winter swims: challenging your body in crisp temperatures has become routine for the health-conscious.
The trend has fuelled sales of dry robes and created a whole industry of wellness retreats that promise to improve your mood, mind, circulation and immune system.
Dutch guru Wim Hof is widely credited with carrying the idea from the fringes of bohemia into the medical mainstream. His ideas have seeped into social media, where the likes of Joe Wicks lie in their own personal ice baths. Everyone from Oprah Winfrey to the Princess of Wales seems to love chilling out.
So popular has the trend become that you’re more likely to worry that you’re a wimp for not doing it, rather than someone with their critical faculties in place.
However, the inquest this week into the tragic death of Kellie Poole has highlighted the fact that cold-water swimming, while invigorating for many, may be hazardous for certain individuals.
The 39-year-old died of an undiagnosed heart condition triggered by the water, a coroner ruled. Her family have called for the regulation of cold water therapy after she collapsed while taking part in a cold-water immersion session in the River Goyt in Derbyshire in April 2022; the water temperature on the day was recorded as 10.7C. Her death was one of a number around the world which have been linked to cold water therapies.
For Mike Tipton, Professor of Human and Applied Physiology at Portsmouth University, the tragedies were sadly all too foreseeable. He has been studying the hazardous responses to cold-water immersion for 40 years, originally working with the RNLI and the Royal Navy who were interested in sea survival. Because of his work, with a team of researchers, we now know about the dangers of cold water shock.
Entering cold water triggers involuntary gasping, rapid breathing or hyperventilating due to the “shock” of sudden immersion, which causes a sudden spike in heart rate and blood pressure. Sixty per cent of those who die going into cold water die from the effects of this cold shock response.
In evolutionary terms, “We’re a tropical animal, we want to be naked in air at about 28 degrees Celsius: if you take a person and plunge them into cold water you’ll get a significant physiological response,” states Tipton.
Research in the aftermath of the sinking of the Titanic led to a widespread understanding of the dangers of cold-water immersion with regard to hypothermia. Now it is understood that the first minute of immersion represents the most significant danger. “That moment where you gasp and have uncontrollable ventilation, there’s a high workload put on your heart,” says Tipton.
The sudden cooling of the skin leads to a cooling of the superficial nerves and muscles which can leave you physically incapacitated within 10 to 20 minutes. “And all of this has occurred before you become hypothermic. There’s absolutely no doubt that going into cold water is amongst the greatest stresses to which you can expose the human body.”
While you can habituate to the cold-water shock response, which will make the experience safer and less likely to result in cardiac problems or drowning, Tipton says: “Going into cold water as a precursor for drowning or cardiac problems is well established with definitive research.”
The benefits meanwhile, are mostly anecdotal. “The definitive studies are yet to be done. There are hypotheses, speculation and anecdotes,” he adds. “But research just hasn’t been done. No one has isolated cold from all the other things that happen when you go into the water like exercise, socialising and being in nature.”
And yet humans have long evangelised the benefits of a chilled plunge. There’s nothing particularly new about Hof and his followers; from the Romans through to Thomas Jefferson and Charles Darwin, cold exposure has had its enthusiasts.
The best explanation for that euphoric rush one feels after cold-water immersion is that the cold shock response releases hormones that are alerting and arousing as part of the fight or flight response. “It’s no surprise that people who do it say it makes them alert and sets them up for the day. It’s the stress response,” says Tipton.
It is a sensation I experienced last Saturday. On a sunny September morning, I jumped (or rather eased myself) into a swimming pond in the Wiltshire countryside. The water was a brisk but not too spine-shattering 15 degrees. I swam two lengths, and then I got out, feeling intensely, almost viscerally alert. Shortly afterwards, I did two more lengths, and posed for a photo with my friends.
Afterwards at lunch, wearing dry clothes and a fluffy jumper, I started to feel not quite myself. Withdrawn, quiet and, most of all, cold. I felt silly compared to my hardier friends who’d stayed in longer; but as soon as I spoke up, they bundled me in extra layers and plied me with hot drinks.
I wondered whether the reason was not only because I am a relative cold-water novice, but also because of my lack of body fat.
When I tell Tipton about my experience, he isn’t surprised by my reaction.
While fat doesn’t protect from the initial responses, because the cold receptors that initiate that response are just 0.18mm below the surface of the skin and lay over the top of subcutaneous fat, that subcutaneous fat does start to help with the cooling of the deeper tissues.
“It has the same thermal character as cork. So it’s quite a good insulator.”
What I experienced was a phenomenon called “afterdrop”, whereby even after you leave the water, the cold front keeps moving into the body and deep body temperature starts to fall.
“It’s why people can be at their coldest 15 minutes after they leave the water,” explains Tipton. “If you don’t institute pretty aggressive rewarming procedures, you can be cold for a long while.”
It’s not the first time I’ve failed to warm to cold-water swimming. Personally, I have found that after the initial rush comes a price not worth paying. A cold-water therapy trip two years ago left me with a two-week cold.
“The evidence shows that if you get too cold it actually diminishes your immune system,” says Tipton.
And yet – full disclosure – I have interviewed the cold water guru Wim Hof in the past and found some of what he said sensible. UK homes are kept 4C warmer than in 1970. Modern, cosy lives mean that our thermoregulation, metabolism and cardiovascular systems have become sluggish. That we’ve become sedentary and thermostatic is also a point Tipton agrees with.
“I do have some sympathy with Wim Hof in that respect, but I have less sympathy with him shouting into a camera that everyone should be going into the water and anyone can do this. Because not everyone can.”
For people with pre-existing conditions and comorbidities, cold-water immersion is a dangerous thing. Guidance from the Association of Chartered Physiotherapists in Cardiac Rehabilitation suggests that water temperatures between 26-33C are safest for people with heart conditions.
In the UK, the water temperatures in natural environments are roughly between 10 and 28C in the summer, falling to between 0 and 7C in the winter. So swimming in a heated pool is likely to be a safer option.
People expect Kate Rew, as the founder of the Outdoor Swimming Society, to be a cold water enthusiast. Somewhat surprisingly, she is not.
“I have never enjoyed winter swimming,” Rew admits. “I’m really rubbish with the cold, so I have full sympathy with people who’ve not got on board with this trend.”
Her worry is that cold-water immersion has been sold as a one-size-fits-all activity, when really there is a huge range of individual variation, from body mass through to pre-existing conditions.
“It’s been quite frustrating watching the dominant narrative of the last couple of years be that cold water is good for your mental health.
“There have been lots of very bold wellness statements that aren’t backed up by science. The truth is we’re not all the same in how we respond to cold. But it’s a narrative that makes people think they should be doing it and it should be good for them.”
Experience has taught her that her sweet spot is about one to two minutes – immediately followed by a sauna.
“When I do it that way, I have a lovely time. But I’ve spent too long trying to become a winter swimmer and sludging up and down wondering why I’m still suffering, hours later.”
Her main piece of advice is that people should follow what feels right to them.
“If people get a buzz from sitting in cold water, that’s great. But I do wonder why we keep turning to gurus to tell us what to do. That’s where people lose track of how it really feels for them.”
In the tragic case of Kellie Poole, her cardiac condition was undiagnosed. This is why Prof Tipton recommends that people should undertake a health check to make sure they are medically fit and healthy before taking part in cold-water swimming.
“This is a significant challenge to human physiology. If you’re going to undertake it, you don’t undertake it lightly.”
He adds: “I’ve got no problem with people wanting to do it but it does need to be done in a safe way with experienced people, preferably in a lifeguarded situation.”
And even if all the right precautions have been taken, Prof Tipton thinks that staying in the water any longer than two minutes is unnecessary. “Most of the benefits people report come from the first two minutes.
“The more you overstay your welcome, the more dangerous it becomes.”
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