Cold Plunge Is Very Popular Right Now, But What Do Doctors and Physiologists Have to Say?

The cold plunge craze is sweeping the globe, promising a multitude of health benefits from boosted mood to pain relief. 

But what’s the real science behind the icy shock? Delve into the depths of this polarizing practice as we uncover the physiological responses, the potential advantages, and the hidden dangers. 

Are you ready to take the plunge and discover if this chilling trend is truly worth the hype?

Intro to Cold Plunges

Cold plunges have long-standing traditions and are now experiencing newfound enthusiasm. However, physiologists warn that the evidence supporting these health benefits is limited. 

Furthermore, the activity carries significant risks. Extreme temperature shifts and cardiovascular strain can trigger heart attacks or even death, according to François Haman, a physiologist at the University of Ottawa in Canada.

“It’s actually extremely dangerous, mainly because everything most people know is from social media. There’s very little knowledge around it,” Haman says. “It’s the biggest jolt a human can experience—like a bolt of lightning. That’s how dangerous it is. You can go into cardiac arrest.”

The Health Trend Emergence

Diving into cold water has a long history in Scandinavia, where people have touted the therapeutic benefits of these activities for centuries. Cold swimming really took off globally during the pandemic lockdowns of 2020.

“It was an activity that people could do relatively safely outdoors together, without having too much direct contact,” says James Mercer, a physiologist at the University of Tromsø in Norway. “For many people, it’s a social activity.”

On social media, many aficionados shared how the cold dips improved their mood and health, creating a global phenomenon. As people sought new ways to stay active and connected during lockdowns, cold plunges became a popular choice, blending physical challenge with social interaction.

Physiological Responses to Cold Water

When your body encounters cold water, it can be shocking—literally. Physiologists call this the “cold shock” response. Temperature receptors in your skin sense the frigid water, triggering the constriction of blood vessels in your extremities to preserve heat in the body’s core. 

This causes you to gasp for air and your heart rate to skyrocket.

“The first few moments after you enter the water, that’s probably the most dangerous part,” says Lee Hill, a former swim coach and exercise physiologist at McMaster University in Hamilton, Ontario. “If you’re not ready for the cold shock, it can be really, really dangerous.”

It’s a powerful response, agrees François Haman, who has worked with the military and special forces. He coaches participants to exhale as they hit the water to counteract the primitive gasping response.

The initial cold response leads to an increase in heart rate and blood pressure, but these changes reverse after several minutes. Known as the mammalian diving response, breathing and blood pressure begin to slow down to below normal levels. 

This ancient evolutionary response has been best studied in marine mammals that dive to astonishing depths. Physiologists believe this response helps conserve oxygen, crucial when holding your breath for long periods.

Evaluating the Health Benefits

Proponents claim cold plunges can improve blood pressure, insulin sensitivity, and decrease inflammation. They also suggest benefits for metabolism and arthritis pain relief. 

While there is some scientific research supporting these claims, Denis Blondin, a thermal physiologist at the University of Sherbrooke in Quebec, notes limitations in existing studies.

Many studies include only a small number of participants, often young men of European descent, which limits broader applicability. Additionally, variations in water temperature, immersion duration, and settings (lab vs. outdoor) make comparisons difficult.

“There’s a lot that we don’t know, and I would say most of the stuff we see in podcasts and such are not things that are definitive and set in stone. We find they tend to over-extrapolate things,” says Blondin.

Mental Health Benefits

Susan Ringwood says going for a swim helps her mentally wash away her worries.

“It’s joyous. It takes all my stresses and puts them in the water. I let it wash concerns into the sea,” Ringwood says.

François Haman agrees. He finds the experience meditative, as do the armed forces members he has trained. The cold water forces them to focus on their breathing and other sensations in the present moment, a habit psychologists call mindfulness.

Studies show that activities like polar plunges and cold showers may help reduce depression. Even a single cold dunk has mood-boosting properties. 

Haman attributes this benefit not only to mindfulness but also to increases in “feel-good” brain chemicals like dopamine produced during cold immersion. He says people also experience a post-polar reduction in the stress hormone cortisol.

Safety and Precautions

Experts emphasize the importance of safety when engaging in cold plunges. François Haman recommends beginners start slowly, getting used to colder water during the fall rather than jumping in during a deep freeze.

“Every human responds to cold differently,” he says. “Cold exposure is not one size fits all.”

Wearing appropriate gear is crucial. While cold plunge enthusiasts may forgo wetsuits, a warm hat, neoprene gloves, and keeping dry clothes and towels ready are essential. These precautions help maintain flexibility and warmth after the plunge.

Understanding your body’s limits is vital. Hands and feet can endure more cold than the trunk, due to the high oxygen and nutrient needs of vital organs. If the body’s core temperature starts dropping, it’s time to get out of the water quickly. 

Recognizing shivering is key: mild shivering generates heat, but intense shivering from central muscle groups indicates the need to warm up immediately.

“If you’ve stopped shivering, your ability to actually generate heat has now stopped,” Hill says. “A light bulb should go off that something is starting to go a little bit south.”


Cold plunges have garnered a following, with enthusiasts promoting a range of physical and mental health benefits. From improved blood pressure and insulin sensitivity to reduced depression and stress, the potential advantages are compelling. However, experts caution that the scientific evidence supporting these claims is limited and often based on small, non-diverse study groups.

The physiological response to cold water is intense and can be dangerous, particularly for those unprepared for the shock. Safety precautions, gradual exposure, and appropriate gear are essential to mitigate risks.

Ultimately, while cold plunges can be invigorating and offer moments of mindfulness, they require a careful approach to ensure safety. Balancing the allure of potential health benefits with the inherent risks is crucial for anyone considering this icy practice.


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