The world record for immersion in ice cubes 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 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.
Are ice baths really dangerous?
Fortunately, the risks of prolonged cold water exposure have been catalogued in a paper called ‘Cold water immersion: Kill or Cure?’ (Tipton et al. 2017). There are principally three: 1) drowning, 2) hypothermia, and 3) cardiac arrest.
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 happens 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.”
In my case, 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.
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 (
What’s important to recognize is that the risk of autonomic conflict only exists when the subjects are attempting a breath hold. Partly for this reason,
The Morozko Method emphasizes structured, continuous breathing while immersed in the Forge.
There are four important safety precautions that mitigate the risks of whole body cold water immersion:
Only Forge sober, and supervise children.
Always enter the Forge feet first, keeping your head above the level of the water.
Allow yourself time to rewarm before driving or doing anything that requires your cognitive attention.
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