mccoy
#21
That’s a very good practice, intermittent cold exposure in air, I practice it in addition to cold water in the morning
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Thiago
#22
For me, it was a good practice, but I was having more vagal tone atrial fibrillation from it.
A good point is that the temperature range in the majority of scientific papers is between 10 to 15 degrees Celsius.
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KarlT
#23
Cold plunge should do the opposite.
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Thiago
#24
Actually not. The initial response is a sympathetic increase, but later is a massive parasympathetic tone increase.
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KarlT
#25
Do you have study to support A. Fib caused by cold exposure?
Thiago
#26
There are several like this one.
But also more about prolonged cold water exposure.
KarlT
#27
I don’t see anything about A. Fib. CWI should slow heart rate. Look up mammalian diving reflex. We use cold water to convert PSVT to normal rates especially in children.
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mccoy
#28
I’ve been keeping with the practice of the morning cold plunge. The body sure adapts to it. This morning outside temperature was at the freezing point, water temperature was 6 °C, the lowest measure so far in my pool. The body did not feel the cold. I stood still for about 6 minutes but I could have gone on, perhaps until numbness and eventually death from hypothermia occurred. No shivering. The shivering usually comes after I warm up inside the home, and I have difficulties in making and drinking hot coffee or cocoa, it spills over.
This adaptation may be at least partly caused by growth of brown fat, which acts as a heating plant, which uses up huge amounts of glucose as a fuel. Brown fat adaptation has been described in one of the latest physionics podcasts.
One trick I found very useful is to don socks, even thin cotton socks will prevent foot numbness, which can make it difficult to climb out the pool and can contribute to a precocious exit from the plunge.
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This is consistent with my understanding of the normal sequence in hypothermia. Once you stop shivering without getting warmer you are in the danger zone. Loss of physical coordination (spilling your cocoa) is also a sign of severe hypothermia.
This paper on adaptive homeostasis says the benefits to be obtained from pushing on the physiological boundaries do not require damage (hormesis)… it’s like in exercise where you want just a bit more than you are ready for…any more stress requires additional recovery with no added gains.
FYI, I just recorded a podcast with Dr Mike T Nelson on this subject….declining adaptive homeostasis as a marker of aging, and how to restore a more youthful homeostatic response (become younger?). Cold therapy is one of several way but should be paired with heat therapy (sauna, hot exercise).
Pat25
#30
I just keep my windows (and doors) open hours per day in autumn/wintertime - whenever air quality levels outdoors seem decent. Temperatures indoors will drop to around 12-14C that way. Not sure if it is enough, but whenever people touch/grab my hand they commonly react as if I’m about to die, so who knows.
In summertime I do nothing though 
I tried cold showers for a while, but I found it absolutely gruesome. It made me not want to shower as a result and I couldn’t get used to it, so I gave up on it altogether.
I posted this study a few years ago - rodent study but was still wondering what others thought of it, but no one responded to it at the time. https://www.nature.com/articles/srep37223
Abstract
In response to cold, brown adipose tissue (BAT) increases its metabolic rate and expands its mass to produce heat required for survival, a process known as BAT recruitment. The mechanistic target of rapamycin complex 1 (mTORC1) controls metabolism, cell growth and proliferation, but its role in regulating BAT recruitment in response to chronic cold stimulation is unknown. Here, we show that cold activates mTORC1 in BAT, an effect that depends on the sympathetic nervous system. Adipocyte-specific mTORC1 loss in mice completely blocks cold-induced BAT expansion and severely impairs mitochondrial biogenesis. Accordingly, mTORC1 loss reduces oxygen consumption and causes a severe defect in BAT oxidative metabolism upon cold exposure. Using in vivo metabolic imaging, metabolomics and transcriptomics, we show that mTORC1 deletion impairs glucose and lipid oxidation, an effect linked to a defect in tricarboxylic acid (TCA) cycle activity. These analyses also reveal a severe defect in nucleotide synthesis in the absence of mTORC1. Overall, these findings demonstrate an essential role for mTORC1 in the regulation of BAT recruitment and metabolism in response to cold.
Pat25
#31
I thought CT mentioned the brown fat thread on the CR Society’s forum, and that is indeed one of the most comprehensive sources I found years ago. I contains a wealth of information, mostly posted by D. Pomerleau. If I remember it well, at the time he used to wear a sort of vest with frozen blocks/packs (I believe he made it himself - not sure).
mccoy
#32
Yes, that thread on CE (cold exposure) was, according to Dan Pomerlau, the most extensive discussion on the subject to be found online. I think I remember that article on mice. I also remember I posted and article on the upstream mTOR signals responsible of the growth of BAT, mainly cold-induced norepinephrine and noradrenaline if I remember well.
I think it’s enough, depending on the amount of dress donned
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mccoy
#33
Joseph, I agree that the over-hormesis region should not be reached, but the optimization would need some study, I remember an article linked by Dr. Sehult, in the times of Covid, where people were immersed in cold water (and it was colder than 6°C) and the beneficial effects on the immune system were described. They stayed for a pretty long time that I remember but again, it would be interesting to find and re-read that article.
Some very generic considerations from the Gemini AI actually tend to be pessimistic about mere survival.
Survival times in 6-degree Celsius water are extremely limited, even for fit individuals.
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Rapid Heat Loss: Heat loss in water this cold is incredibly fast. Core body temperature can drop dangerously low within minutes.
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Risk of Drowning: Cold water shock can lead to gasping, rapid heart rate, and potential loss of breath control, significantly increasing the risk of drowning.
Important Note: This is a general estimate. Individual survival times can vary greatly depending on factors like:
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Physical Condition: Age, health, fitness level.
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Body Fat: Higher body fat provides some insulation.
I don’t know why in my case shivering happens after the exposure, maybe it takes time to lower the body core temperature below the safe limit and trigger this involuntary heating mechanism. That is: the core temperature keeps lowering even after the plunge and in warm environment, maybe. Or maybe something in the water inhibits shivering.
Cold shock is very easily avoided by entering cold water very slowly.
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mccoy
#34
These are more realistic data on survival, also coherent with my experiences and recounts from other people.
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@mccoy Dont get me wrong on this topic. It is impressive that you can do this. I know how hard it is to learn to tolerate the cold. I also know from personal experience that it becomes addicting (the torture and the dopamine rush afterwards). But of course be careful when you are alone in water doing physiologically stressful activities. A little too much might be the end. But this wasn’t my point.
My point was the benefits (becoming “younger”) to be gained from cold are also available from other modalities: heat, fuel usage extremes, pH stress extremes, co2 tolerance. The paper I linked previously speaks to the idea of adaptive homeostasis as a measure of aging, and that losing the ability to adapt is a marker of getting older, and that we can train the body to return to a more youthful adaptive response. So, my point is there is no need to push so hard on cold adaptation. In fact it might be better to train your body on multiple dimensions of stress.
I agree: I am sure it is a beneficial stress-test. Fortunately viking axes nor 130 metre dives are possible in my London borough. I’m sure I’d be gasping to do this otherwise. 
mccoy
#37
Ah, yes, I agree, you can rest assured that I’m not pushing hard, but since it’s the first season I practice cold plunges (previously it was cold showers) I’m just a little curious.
The internet is full of images of people plunging in freezing waters. I am just a wimp in comparison. This lady, relaxing in the iced water of lake Michigan, is 80.
Heat and other stressors: I also used to practice heat exposure under the sun for a few seasons, but I find I cannot tolerate UV radiation unless the exposure is very gradual. Also, last summer it was so hot here that I felt pretty fatigued and adding more heat felt almost a suicide. Heat is ideal after cold, since the two combine well together, the body craves heat after intense cold and vice versa.
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mccoy
#38
The body is adapting ever more to these cold plunges. This morning, with water at 6°C, if I stayed still I found I was missing the cold stressor and had to move around a little to feel the low temperature.
Immediate advantages I’m feeling: a powerful injection of natural norepinephrine and other neurotransmitters which really wake me up, especially so if the head is plunged (usually at the end). Another benefit is the strong impulse to do some cardio activity to warm up, it comes naturally and effortlessly.
Disadvantages: it takes time to warm up afterward. I’m limiting the plunging time to a few minutes so that I do not reach the shivering state afterward.
Long-time benefits: I hope a boost of the immune system. Some fat brown hypertrophy as well, although this would be dependent upon subsequent cold-air exposure, which I’m practicing as well but to a lesser extent this year.
mccoy
#39
This is an interesting review on the topic, which apparently is still subject to debate.
Actually, increase in T cells and other macrophages has been cited among the effects of cold water immersion. All in all, the cited effectsof CWI do seem to be beneficial.
Here is my episode with Dr Mike T Nelson on Adaptive Homeostasis…expanding your body’s ability to adapt to extreme internal and external environments to improve health, athletic performance, and how old you feel…
Update: See reference to Hallmarks of Health
Dr Mike presents a framework for intelligently using extremes to make your body more like it was when you were younger. Is that the same as being younger? No, but I’ll take it. I restarted my cold showers this morning to add to my regular sauna usage. I’m also re-starting my O2 deprivation training to my ongoing high CO2 tolerance training.
I hope you like it.
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