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Can people warm or cool their bodies using only their thoughts? Wency Leung investigates the physiological effects of meditation and breathing techniques in extreme environments

Wim Hof of the Netherlands, known as the Iceman, prepares for a performance in a tank of ice for German Television, in Inzell, Germany.

Vitina Blumenthal rolled out her yoga mat on the back patio of the Nicaragua hotel, where she was recently leading a wellness retreat. Seeking relief from the 35-degree Celsius heat, she sat down, cross-legged, with her hands in her lap.

The Toronto mindfulness coach straightened her spine, closed her eyes and took three deep breaths. Then, curling up the sides of her tongue and sticking it out, she slowly inhaled through the tunnel she had formed, and exhaled.

After repeating this several times, she could feel herself becoming calmer, lighter and less bothered by the oppressive heat.

"I get really overwhelmed sometimes when I'm super-heated and I can feel frustrated," says Blumenthal, founder of the luxury wellness travel company WanderfulSoul. "That breath is a nice way to kind of trick the mind that you're now cool."

Blumenthal, who has been practising yoga for more than a decade, explains she learned the meditative breathing technique, called sitali, while living in an ashram in India. Whenever she feels unbearably hot, she uses the technique to make herself feel cooler, whether she's travelling abroad or riding out a humid Toronto heat wave.

Meditative techniques for regulating body temperature are part of ancient spiritual practices.

Yoga practitioners, for instance, refer to sitali and the similar sitkara, which involves positioning the tongue just behind the teeth, as breathing exercises that lower one's body temperature.

Other yoga breathing exercises such as kapalbhati, which involves forceful breaths using the diaphragm, are meant to increase body heat. Tibetan Buddhist monks and nuns are known to practice tummo meditation, which is believed to create "inner fire," allowing them to withstand frigid temperatures.

Similarly, Wim Hof, a daredevil from the Netherlands, is renowned for incredible feats such as submerging himself in ice for more than an hour at a time and climbing Mount Everest clothed in only a pair of shorts.

He attributes his seemingly superhuman resilience to his eponymous method of breathing and meditation exercises.

Such phenomena have prompted researchers to investigate the physiological effects of meditation on body temperature. Can people actually think their way to becoming hotter or cooler?

Tibetan Buddhist monks and nuns are known to practice tummo meditation, which is believed to create “inner fire,” allowing them to withstand frigid temperatures.

Inner fire

One of the first Western scientists to examine this type of meditative practice is Dr. Herbert Benson, a mind body professor of medicine at Harvard Medical School and now director emeritus of the Benson-Henry Institute for Mind Body Medicine at Massachusetts General Hospital. In February, 1981, Benson and his team travelled to the Himalayan town of Upper Dharamsala in India to study monks as they practised tummo meditation.

As they reported in a 1982 paper published in the journal Nature, the only descriptions of this esoteric practice that existed previously were unscientific eye-witness accounts. These depicted novice monks sitting naked and cross-legged on the ground, then wrapping themselves with sheets dipped in icy water. The men were then said to have dried the sheets with their body heat.

Benson says he observed seasoned monks practising tummo meditation in temperatures of 4 C to 10 C. He noticed they first entered what he calls a "relaxation response" state, which he describes as the opposite of the "fight or flight" stress response, slowing their breaths and settling into a deep rest. Then, they visualized their bodies being heated by fire, which they explained comes from "the scattered consciousness," he says.

"The purpose of that is to burn away the harmful effects of stress," Benson says, noting that at such low environmental temperatures, "You and I would go into uncontrollable shivering. [But] here, they were able to actually have the sheets steam on their bodies. That was for them, a sign of successful meditation."

Benson and his team took a number of measurements of three monks, aged 46 to 59, including temperatures of various parts of their body. They recorded no change in their rectal temperature, but found the monks were able to increase the temperature of their fingers and toes by as much as 8.3 C.

"This was fascinating," Benson says. He noted the monks were able to keep their peripheral body temperature raised for as long as they were visualizing heat generated in the body.

The question, though, is how? Benson never found the answer. After the study was complete, he didn't end up researching tummo further. The financial costs of returning to India were too high, he says, and instead, he turned his attention to examining the impact of meditation on health issues such as high blood pressure.

Mental imagery

Dr. Maria Kozhevnikov has since picked up where Benson and his team left off.

Kozhevnikov, an associate professor of psychology at the National University of Singapore, has studied the physiological effects of Vajrayana techniques (Vajrayana is another name for Tantric Buddhism), including tummo meditation, on practitioners in Nepal, the Chinese province of Qinghai (also known as eastern Tibet) and Bhutan. Unlike mindfulness practices that induce relaxation, Vajrayana techniques elicit an arousal response controlled by the sympathetic nervous system, she explains.

Practitioners "use stress to go to a higher state of consciousness, not a relaxed state of mind," she says. So contrary to what Benson believed he observed, practitioners of tummo and other Vajrayana techniques don't dial down the stress response during meditation; they actively crank it up, she found.

Kozhevnikov, who is also a visiting associate professor of radiology at Harvard Medical School and specializes in the neural mechanisms of visual imagery, believes the answer to how tummo practitioners raise their body temperature consists of two parts: breathing and intense visualization.

The breathing, which in tummo practice is forceful and involves abdominal and pelvic muscle contractions, "is not that interesting," she says. Rather, it's just one of a few mundane techniques, such as engaging in physical exercise, that allow people to increase their core body temperature to a certain point. Typically, once they hit 37 C, the body's cooling mechanisms automatically kick in. They start to sweat, their blood vessels dilate and they're unable to raise their body temperature any further.

This is where she believes intense visualization comes in. In tummo meditation, practitioners conjure mental images, such as flames, and imagine sensations of intense heat. Kozhevnikov suggests this visualization allows practitioners to override the body's automatic cooling response, allowing them to push past their typical threshold.

"By using the visualization, apparently, the body doesn't understand what's happening and they can go on and on and on, and higher … than 37" degrees, she says.

Kozhevnikov says she's still trying to figure out how visualization may produce this overriding effect. This summer, she has been recording the brain activity of nuns in Bhutan using electroencephalography as part of her efforts to understand the mechanisms at work.

Wim Hof immerses in ice water during a performance to arouse the public awareness of global warming in Hong Kong.

Acclimatization training

Some scientists are skeptical that this kind of body-temperature regulation can be explained by the powers of the mind. Dr. Maria Hopman, professor of integrative physiology at Radboud University in the Netherlands, thinks the answers are likely more physical than mental.

Hopman has performed several highly publicized experiments on Hof, also known as "The Iceman," whose training method has gained followers around the world.

One of her most "amazing" findings, she says, was Hof's ability to maintain his core body temperature at close to 37 C, even after an hour and a half of being submerged in ice water, while his skin temperature plummeted. Hopman believes the main factor behind his resilience appears to be his vasoconstriction ability, or his ability to reduce blood flow to the skin in response to cold, so that he doesn't lose too much heat. She suggests he has acquired this ability over many years of training.

Even though Hof's method involves meditation and breathing exercises and is described as similar to tummo and yogic breathing, Hopman says she has witnessed him perform stunts in extreme cold without much time to meditate in preparation.

"I don't know that the meditation is so important," she says. "I think the most important thing is the training and the adjustment of the body."

If you were to take daily minute-long cold showers, for instance, and gradually increase the length of your showers over time, you'd likely be able to withstand a 15-minute cold shower by the end of a year, Hopman says. "I really think it's an adaptation of the body as you exposure yourself to it regularly."

Hopman notes Hof's extraordinary abilities do not extend to tolerating heat. One of her colleagues once studied him as he ran a marathon in the heat of a desert in Namibia, she says, noting, "He was not extremely good at it. He really was not any better than anyone else with some strength and a fit body."

Cooling down

If these hypotheses provide possible explanations for how one might keep warm in cold temperatures, what could be behind yoga and meditation techniques that are meant to cool you down?

Indeed, it's possible to improve your tolerance to heat through similar repeated exposure. For instance, Bikram yoga, which is practised in a heated room, can be considered a form of heat training, says Dr. Jessica Mee, a lecturer and researcher in the school of sport, health and exercise sciences at Bangor University in Wales. Typically, after 15 sessions over four weeks, people start to experience certain physical adaptations that allow them to better cope in heat, such as an increase in sweating, more dilute sweat, and lower cardiovascular strain, she says. These adaptations may, over time, help you feel less uncomfortable in heat and become more efficient at cooling yourself down.

The acute effects of specific cooling postures and breathing techniques, however, such as the sitali breathing that Blumenthal practices, are not well studied. While they're widely recognized and practised in yoga, there's a lack of scientific literature on the effects of these techniques on body temperature, Mee says.

But ultimately, Mee explains, our body temperature is dictated by our heat storage, which is determined by our heat production, or metabolic rate, and our ability to lose heat, which is typically through the evaporation of sweat. She suggests certain meditation and breathing techniques may help relax the body, reducing one's metabolic rate to resting levels.

"So when we're rested or calm and in a meditative state, you would likely expect a lower heat production," she says, noting this is likely achieved through multiple responses including a lower heart rate, a lower respiratory rate and less skeletal muscle activity.

Bikram yoga, which is practised in a heated room, can be considered a form of heat training, says Dr. Jessica Mee.

Psychological resilience

None of these practices for consciously controlling one's body temperature are particularly mystical, says Dr. Norman Farb, an assistant professor of psychology at the University of Toronto Mississauga.

But he suggests our bodies may be capable of more than we think. How we interpret our state of being hot or cold can contribute to how well we tolerate extreme temperatures, he says. For example, he explains, if we feel as though the summer heat is unbearable, the stress of that discomfort can itself affect our physiology, such as causing our heart rates to increase and our metabolism to speed up, thus making us even hotter and making the situation feel worse.

"That's going to create a vicious cycle, like, 'Oh, it's too hot, and now I'm getting stressed about getting too hot and so I feel even hotter and I get more stressed,'" Farb says, noting many meditation practices are aimed at helping people distinguish between the primary sensation of what they're experiencing and the interpretive layer they add on top.

"If you can stay with the primary sensation, it lends itself to psychological resilience because the things that often make people quit or or panic or fail are appraisals that they can't cope," he says.

Blumenthal, the Toronto mindfulness coach, believes this is what sitali enables her to do. While it may not actually change her body temperature, it calms her nerves and relieves her frustration over the heat, allowing her to better deal with the sweltering weather, she says.

Farb warns, however, that the body still has its physical limits. People who are good at breaking away from their concerns about the heat or cold may actually put themselves at risk of becoming overheated or making themselves vulnerable to hypothermia.

"It isn't always just mind over matter," he says. "You could get to the point where you still freeze to death or overheat. And in fact, this is a practice that would let you get to that place."