Updated: Aug 4
Three dangers associated with ice baths and cold plunging are: drowning, hypothermia, & heart attack.
To minimize these risks follow these safety protocols: 1) avoid contraindications, 2) plunge sober, 3) supervise children, 4) go feet first, 5) breathe, and 6) allow time to rewarm.
WARNING: Never combine hyperventilation with cold water swimming. Do not attempt breath holds while in the water.
Are ice baths dangerous?
Investigative journalist Scott Carney has documented more than a dozen deaths associated with (mal)practice of the Wim Hof Method (Carney 2023). Although Carney credits Hof's training for giving him "superhuman levels of endurance" and helping to "quiet a persistent autoimmune illness," Carney also cautions that combining Hof's hyperventilation techniques with cold water swimming can result in shallow water blackout -- a condition that causes underwater loss of consciousness and drowning.
Carney is careful to point out that neither hyperventilation nor cold water immersion are particularly dangerous when practiced separately. They only become dangers when they are combined.
Hyperventilation purges the body of carbon dioxide. Because it is accumulation of carbon dioxide in the bloodstream (not a deficit of oxygen) that creates the urge to breathe, swimmers who hyperventilate prior to their plunge may not feel the urge to breathe before they lose consciousness from lack of oxygen.
The drownings Carney has documented are preceded by passing out. To minimize the risks of the Wim Hof Method, both Carney and written instructions on the Wim Hof website caution practitioners that they should never practice hyperventilation or breath holds while in the water.
Dangers of Deliberate Cold Exposure
The deaths Carney has documented have not resulted from the cold exposure itself, but from loss of consciousness in the water. When most people think of the dangers of cold itself, the first thing that comes to mind is hypothermia.
In her book The Upside of Stress (2012, p186), Stanford Professor Kelly McGonigal claims that "Below five degrees, water becomes so painfully cold that it feels like it is burning your skin. If you were to immerse your whole body in water this cold, it would kill you in less than a minute."
The world record for whole-body cold immersion is 150 minutes. While Wim Hof is most famous for popularizing cold exposure, the record is now held by an Austrian man named Josef Koeberl.
Given McGonigal's claims, and the fact that Wikipedia claims that the shock of the cold water could lead to "sudden death," daredevils like Koeberl and Hof might cause us to question how they could survive such prolonged exposures.
For a long time, my personal best was 14 minutes in my Forge, and the effects were considerable. When I emerged, it felt like every muscle in my body was trembling. I had lost all fine motor control, which made using my mobile phone or driving my car impossible.
It took about ten minutes to rewarm enough so that I could drive myself to hot yoga, and even then it probably wasn't a good idea.
In 'Getting Started with Cold Therapy' I wrote about some of the risks, but even though I've stated in the past that "every cell in my body is trying to tell my brain that I'm going to die," the Wikipedia claims looks exaggerated and unsubstantiated to me.
The most dangerous thing about my 14 minute ice bath was probably the 20 minute drive I made afterwards.
Cold Water Risks
Fortunately, three of the risks of cold water exposure have been catalogued in a paper called 'Cold water immersion: Kill or Cure?' (Tipton et al. 2017): 1) drowning, 2) hypothermia, and 3) cardiac arrest. To them I will also add: 4) operating during rewarm,
Drowning occurs when water is inhaled into the lungs, suffocating the victim. I could not find a single study or documented case of drowning in an ice bath, although there is a phenomenon in Japan called 'Dead in Hot Bathtub' (Satoh et al. 2013). It might come as no surprise that drugs and alcohol are often contributing factors in bathtub drownings among adults (e.g., Peden et al. 2019, Okuda et al. 2015), but young children can also be at risk (e.g., Orlowski 1987). This suggests two things: 1) Forge sober, and 2) children should never be permitted in the Forge unsupervised.
But there is something particular about cold water immersion that is also worthy of mention, called the "gasp reflex" (Mekjavic et al. 1987). When our bodies enter cold water, we experience an involuntary urge to suck in our breath -- like author AJ Kay in the video posted at right.
If we are unable to control the gasp reflex while our mouth and nose is covered with water, we may accidentally inhale water and be at risk of drowning. For this reason:
Always Forge feet first.
Hypothermia is when core body temperature drops two-and-a-half or more degrees below normal (Jolly & Ghezi 1992). According to Tipton et al. 2017, the risk of hypothermia from cold water immersion progresses through four stages:
The first three minutes cool the skin,
Three to about thirty minutes results in superficial neuromuscular cooling,
Longer-term immersion (greater than thirty minutes) can pose a risk of hypothermia by inducing deep tissue cooling.
One of the amazing things about cold water immersion is that "cold can protect life as well as endanger it" (Harries 2003). Unlike hypothermia induced by frigid air, which can result in frostbite, liquid cold water is insufficient to freeze human cells. Thus, even victims of cold water drowning can survive prolonged periods without breathing or a pulse, when arriving at the emergency room in a hypothermic state. Weinberg 1993 cautions, "although the clinical presentation may be such that the victim appears dead, aggressive management may allow successful resuscitation in many instances."
Go cold enough to gasp, long enough to shiver.
Operating during rewarm refers to the impairment that is typically part of recovering from cold exposure. For example, driving a car is a dangerous activity that demands full command of the senses and extremities. A person should allow sufficient time for full rewarming before attempting to operate a motor vehicle, hand tools, or do anything else dangerous.
After my 14 minute ice bath, afterdrop was probably a more serious concern than hypothermia. During cold immersion, the human body will automatically employ vasoconstriction to limit blood flow to the extremities and conserve heat for the vital functions in the core. When emerging from the ice bath, blood returns to the cold limbs and begins rewarming the muscles. But the blood that goes through the extremities must eventually return to the heart. Afterdrop is a phenomenon in which the core body temperature continues to fall even while rewarming, because blood returning to the core is colder after having passed thru the frigid arms and legs (Romet 1988).
While it's unlikely that afterdrop poses a serious physiological risk, Seo et al. (2013) have investigated the psychological effects of afterdrop and suggested that subjects experience cognitive and attentive impairment as their core temperatures return to normal.
That's why it was a bad idea for me to drive so soon after an extended ice bath.
Rewarm before operating machines or tools.
The most complicated, and hypothetical, of all the dangers described in the 'Kill or Cure' paper is related to cardiac arrest.
When our faces are submerged in water, our bodies automatically slow down our heart rate and metabolism to conserve oxygen -- a phenomenon first documented in 1875 and now called "the dive reflex" (Wolf 1965). The heart rate response to breath is now well-documented. In the extreme, reductions in heart rate of 44% have been observed in elite, breath-hold free divers (Lamaitre et al. 2005).
However, Tipton et al. (2017) hypothesize that when cold water swimming, a conflict between the gasp reflex (from immersion in cold water) and the dive reflex (from holding our breath) emerges that confuses the signals that control heart rate. They write, "Perhaps one of the most powerful and reproducible ways of inducing autonomic conflict is by rapid submersion in cold water (<15°C) with attempted breath holding. This activates two powerful autonomic responses: (i) the cold shock response (i.e., gasp reflex), and (ii) the diving response." According to their hypothesis, autonomic conflict can lead to an irregular heart beat or a fatal cardiac arrest that would be undetectable in an autopsy.
What's important to recognize is that the risk of autonomic conflict only exists when the subjects are attempting a breath hold.
The Morozko Method emphasizes structured, continuous breathing while practicing whole-body cold water immersion.
Shallow water blackout
Investigative journalist Scott Carney has documented more than a dozen cases of drowning during practice of the Wim Hof Method that can be attributed to loss of consciousness while in the water. Because the Method involves hyperventilation prior to cold water immersion, practitioners who attempt breath holds under water may lose what is called the "urge to breathe" and deplete their oxygen stores.
This tragic phenomenon is all too common among free divers (diving without the use of underwater breathing apparatus).
Inexperienced or untrained divers frequently hyperventilate before diving to increase their blood oxygen levels. This method is dangerous as hyperventilation causes them to expel large volumes of carbon dioxide, lowering their pre-dive carbon dioxide levels. They, therefore, experience the "urge to breathe" much later in the dive, which may lead to an underwater blackout. This mostly happens because the diver has depleted their oxygen stores before reaching the blood pH threshold to trigger the "urge to breathe", which would have alerted them to return to the surface. - Allen & Allen (2022)
To mitigate the danger of shallow water blackout, never, ever combine hyperventilation with underwater breath holds. To obtain the benefits of the ice bath, and minimize the risks, it is essential to breathe during the experience.
Never combine hyperventilation with water immersion.
Ice bath safety
There are several precautionary protocols that mitigate the risks of whole body cold water immersion:
Avoid cold water immersion when contraindicated or contravened by advice of your physician. As I wrote in Contraindications to Cold Plunge, hypertension, heart arrhythmia, anorexia, cold urticaria, anti-depressants, are examples of contraindications.
Ice bath sober. Never enter the water while intoxicated, inebriated, hyperventilated, feeling faint, or under the influence of drugs.
Supervise children. Drowning is the leasing cause of death among American children aged 1-4, and the second leading cause for children 5-14 (CDC 2022). Young children must always be attended by a capable adult when bathing.
Enter the ice bath feet first to allow yourself to experience the gasp reflex, and to give your body time to structure your breathing and strengthen your parasympathetic response.
Breathe continuously, in a steady, structured rhythm. Never combine hyperventilation with immersion in the water and do not attempt breath holds in the ice bath. For example, when dunking your head, exhale slowly to maintain your breath.
Go cold enough to gasp, long enough to shiver. The benefits of the ice bath come in the first few minutes, while the risk of hypothermia increases later. Especially for beginning plungers, there’s no reason to immerse any longer than it takes to induce a shiver response.
Allow time to rewarm before operating tools, machinery, a vehicle, or any other equipment.
For more information on taking charge of your own physical & mental health, visit the Self-Actual Engineering newsletter at https://seagertp.substack.com/.
For personal stories about journeying through the cold, listen to The Morozko Method podcast https://anchor.fm/adrienne68.