Early every Sunday as day breaks over the ocean, 50 or so people gather in the park behind Sydney's Bronte Beach to breathe together before plunging into ice.
One by one they lower themselves into the freezing tubs, while someone next to them sets a timer for two minutes. As the seconds slowly tick over, they focus and breathe, until they climb out with relief.
Ice Baths Sydney is run by Deb Sarah, who became an advocate for cold water therapy after breaking her spine in a car accident at the age of 21.
"I transitioned from an active high achiever to someone struggling with chronic pain and anxiety," she told SBS News.
In analysing her lifestyle and searching for ways to numb her pain and relieve her stress, she discovered cold exposure.
"It's an incredible way to build resilience in the mind as well as the body. When you see someone thinking that they cannot do it, to sitting in an ice bath, sitting in the pain for two minutes, the transformation that can have in the rest of their lives is quite impactful."
Sarah says cold exposure helps her to manage her daily emotions.
"When I get very stressed or overwhelmed, the ice bath brings me back into my body and feelings and reconnects me with myself."
Deb Sarah, who runs Ice Baths Sydney, says her Sunday morning sessions are about "connection, building resilience and reducing stress". Source: Supplied
"I like to do it for mental clarity and stability. I like the challenge of it," he told SBS News. "I like being able to sit in the discomfort and feel my heart rate completely slow down."
When he misses a day, he doesn't feel quite the same.
"I just feel kind of scattered, a bit all over the place. It's part of my daily mental and spiritual practice and I like how I feel afterwards. It's become pretty important."
Dallas Renshaw takes a daily ice bath to maintain his mental health and to reduce muscle inflammation post-exercise. Source: Supplied
Study shows some benefits of cold therapy, but results are inconclusive
The popularity of ice baths, cold showers and blue swims has exploded across the world in recent years, mainly as a result of the Wim Hof Method (WHM), devised by Dutch motivational speaker Wim Hof.
The method is based around a system of intentional breathing followed by cold therapy such as an ice bath or cold shower on a regular basis.
Hof claims his method unlocks a range of benefits, including increased energy, better sleep, reduced stress levels, heightened focus and determination, increased willpower and a stronger immune system.
While various studies have found evidence of the benefits of cold exposure, a new UK study is the first to support the scientific benefits of the WHM specifically, notably that it increases adrenaline as well as anti-inflammatory chemicals called cytokines.
"The findings suggest that the WHM may reduce inflammation in healthy and non-healthy participants as it increases epinephrine levels, causing an increase in interleukin-10 and a decrease in pro-inflammatory cytokines," says the study, named 'Does the Wim Hof Method have a beneficial impact on physiological and psychological outcomes in healthy and non-healthy participants? A systematic review', which reviewed data in eight published trials on the WHM.
But while there were positive findings, the data was also inconclusive.
"Despite the statistical significance observed in some studies, it must be noted that the quality of the studies is very low, meaning that all the results must be interpreted with caution," said authors Omar Almahayni and Lucy Hammond from the University of Warwick.
They added that more research was needed to analyse the method's impact on stress, inflammation, exercise and overall health.
'Leaves us feeling calmer'
Psychologist Emanuella Noble says while she can't comment on ice baths specifically, the link between cold and stress relief is clear.
"When we are stressed, our sympathetic nervous system is activated — the fight-flight-freeze response — more so than our parasympathetic nervous system, which relaxes the body. We need a balance between these two systems to feel calm," she told SBS News.
"An important part of the parasympathetic nervous system is the vagus nerve. What the research has found is when we expose our bodies to cold, the vagus nerve is stimulated and as our body adjusts to the cold, it can reduce the flight-flight-freeze response and increase the parasympathetic nervous system activity,"
Dr James Ibrahim at the Royal Australian College of General Practitioners says while this UK study may be the first to look at the WHM, others have already linked cold therapy to physical and mental health benefits.
These include improved delayed onset muscle soreness, especially after high-intensity exercise, and increased levels of norepinephrine (an organic chemical in the brain and body that helps to mobilise the brain and body for action) and dopamine (an organic chemical that acts on areas of the brain to give you feelings of pleasure, satisfaction and motivation), he said.
Studies have shown that cold exposure can increase levels of certain chemicals in the brain, such as dopamine. Source: Supplied
"I wouldn't use it as an intervention for someone with severe or high-risk depression or mental health issues. But if someone's got very mild to moderate depression and there's an element of behavioural activation that they're lacking, then cold water treatment is definitely a useful adjunct to their treatment plan," he told SBS News.
"And I clinically suggest it almost on a daily basis in consultations with people who for various reasons have issues with their sleep ... Cold showers are a great way to start the day."
He adds that people with musculoskeletal or connective tissue issues may also find "quite significant symptom relief with cold therapy", though he cautions there are limitations.
"I'd be very wary to tout it as a potential treatment for undiagnosed or poorly differentiated symptoms, which may suggest underlying disorders or things that have not been properly diagnosed.
"Cold therapy is not going to be a panacea, but with inflammatory conditions it can really make a profound impact on people's quality of life among other lifestyle changes."
But Ibrahim warns there are risks to the breath work associated with the WHM, particularly if performed unsupervised.
"Anytime you are trying to regulate your own breathing without leaving your autonomic nervous system to do the job, you are at risk of changing the way that your body manages its oxygenation and carbon dioxide levels. You can actually end up in a state of hypoxia, which is an absence of enough oxygen, and your body doesn't get the urge to breathe."
Wim Hof, the Guinness World Record holder for his ability to withstand extreme coldness, immerses himself in ice water during a performance to raise public awareness of global warming in Hong Kong in 2010. Source: AAP / Kin Cheung / AP
How cold and for how long?
When people ask how often they should expose themselves to the cold to reap the benefits, it's not easy to give them an answer, Ibrahim says. This is because it depends on how much body fat they have (the less fat, the faster the body will cool), and how long they plan to immerse themselves.
"If they're looking to induce a peak in their norepinephrine levels and dopamine levels, I always say cold showers are a great, or if you can't tolerate that, a splash of cold water on the face and chest," he said.
"But if you're looking for musculoskeletal benefits such as delayed onset muscle soreness, I think you really need a cold plunge or immersion of some sort, and the more of your body that's in the water, the better."
Common advice suggests water below 15C is optimal, which is the approximate temperature of cold tap water. While cold water used for sports performance-related therapy is typically five to 10C, Ibrahim says.
Noble adds that people don't need to rush out and buy an ice bath, which can cost anything between $50 and $8,000.
"We know holding ice in our hands for a short period, running our hands or wrists under cold water, splashing water on our face, or having a cold shower for 10 seconds can sometimes do the trick," she said.
Sarah says her Sunday morning sessions are primarily about "connection and building resilience and reducing stress".
"To sit there in the ice bath and watch the sunrise and do the breath work, and be in the present moment with the people ... it's really quite beautiful."
Medical experts advise that cold water can cause cold water shock and hypothermia, and can impact people of all ages and fitness, including even the most capable swimmers.
