Stop shivering and get cold! (especially for Naiad)

[trux]

From the American Physiologic Society:

Seals Shiver In The Cold Air But Not During An Icy Dive

Physiological adaptation conserves oxygen, protects brain

Virginia Beach, Va (October 10, 2006) – Seals shiver when exposed to cold air but not when diving in chilly water, a finding that researchers believe allows the diving seal to conserve oxygen and minimize brain damage that could result from long dives.

The research provides insight into how seals allow their bodies to cool (become hypothermic) during a dive, presumably to better cope with a lack of oxygen (hypoxia). Research into hypothermia and hypoxia is important because they are problems that affect people under a variety of circumstances. Doctors often are called upon to treat people who have suffered accidental hypothermia, for example, as a result of falling into the ocean or becoming lost during the winter. In addition, several hundred thousand people die or are irreversibly injured each year following cardiac arrest, stroke or respiratory disorders which cause inadequate oxygen supply to the brain, Folkow explained.

Folkow will present a second study on hypoxia, involving diving birds, at the conference. The study “Neuronal hypoxic tolerance in diving birds and mammals,” examines how diving birds and seals preserve brain cell function in the face of oxygen deficits. The study is by Folkow, Stian Ludvigsen and Blix, of the University of Tromsш and Jan-Marino Ramirez of the University of Chicago.

Shivers produce warmth
Shivering is an involuntary response that consists of muscle contractions which produce warmth. Mammals and birds are physiologically programmed to shiver when body temperature drops below a certain “set-point.”
While breathing air, seals shiver just like other animals. But when they dive below the surface in frigid water, shivering is switched off, the study found.

By shutting down the shivering response, a seal allows its body temperature to drop and achieves the benefits of hypothermia: a slower metabolism and lowered oxygen requirements which extends the dive time, Folkow said.

Taking the plunge
The seal experiment took place in a tank in which the seals took a series of experimental dives into cold water of 2-3° C. The researchers recorded shivering, heart rate, brain temperature and rectal temperature while the seals were on the surface and while they were diving.

The seals shivered on the surface but stopped or nearly stopped shivering when they dove, even though their bodies continued to cool. Their heart rates and temperatures dropped while they dove, but when they returned to the surface they restarted their shivering nearly immediately.

Seals have a remarkable capacity to store oxygen in their blood and muscles – four times as much as humans – to which they add this oxygen-conserving step of not shivering, Folkow said. By allowing body temperatures to drop, they slow metabolism and reduce oxygen demand. In addition, since shivering itself requires oxygen, there is an oxygen-conserving advantage to not shivering when diving.

In addition to slowing metabolism and generally reducing the need for oxygen, the researchers found that the seal’s brain may cool about 3° C during the dives. The cooler brain requires less energy and oxygen and reduces the chance of damage caused by hypoxia, Folkow explained.

Achieved while remaining active
Seals have this physiological adaptation available just in case. This study found the seals can dive to more than 1,000 meters and for more than an hour. However, they usually take dives much shorter than their maximum capacity, and only occasionally perform very long dives. By limiting dive duration, seals maintain aerobic metabolism, avoid lactate buildup that occurs in the face of insufficient oxygen and require little time to recover, Folkow explained. Seals often spend 80-90% of their time at sea underwater, he said.

Seals in the wild occasionally dive for so long that they use nearly all their oxygen, but they can recover with these special adaptations. Humans cannot tolerate oxygen levels nearly so low as a seal can.
“Somehow they tolerate hypoxia better, we don’t know why,” Folkow said. The study of how seals handle this lack of oxygen may someday give us knowledge that is useful in treating people who have suffered severe hypoxia, although those advances are likely years in the future, he added.

[Waterenthusiast]

That's very interesting, but to transpose this statement on our diving methods is not that easy, at least not for me. I start shivering quite fast, which might be related to my very low BMI and quite non existent Bioprene. Although i can postpone the start of shivering by concentration, once it started i's quite impossible for me to stop shaking around. But with some practice i think a slight adaptation will occur.
Now is the winter season, time for some cold lake diving

Christophe

[TRITON]

I've noticed something interesting....when training or at the competition I sometimes get cold and eventually start to shiver...but when I start my dive the shivering decreases substantially or even stops completely , and starts again when I start to breath.

[Erik]

This is noticeable to many cold-water divers too. Even holding your breath at the surface will stop shivering if you're in cold water and have started shivering. Eventually I get to the point where I'll shiver underwater too and then it's definitely time to stop.
Eric Fattah showed me how to stop shivering at the surface: hold your breath to 10 contractions.

[naiad]

Trux, thanks for thinking of me.
I do stop shivering at the start of apnea, even if I was shivering before I started. The problem is that if the apnea lasts more than about 2 minutes, the shivering starts again. Also, eventually the shivering at the surface can get so bad that it causes lactic acid buildup, so it is impossible to start a dynamic in a good state.

Maybe there are two problems. One is that I don't have much of a dive reflex, so the shivering does happen during apnea. The other is that any activity, including shivering, causes an unusual amount of muscle fatigue.

There may be many factors involved. When I did some 'freediving' in water of 10-12c, with normal clothes and no suit, I did not get huge spasms of shivering. This could be because the air temperature was warm and it was a sunny day. Getting into a much warmer pool of 25-26c can cause much more shivering if the surrounding air is cold.

[BennyB]

Interesting. In cold water (13-14 deg) I tend not to shiver on my dives, actually I don't really shiver on the surface either, but if I do it stops in the dive. When i'm cold and shivering I tense up, and if I kind of relax it seems to release that cold tension and stops the shivering.

Yet in the pool for statics (and sometimes dynamic) I will shiver if I feel cold, though relatively we're talking 23-25 deg which is a lot warmer than the quarry. In my static at the Worlds this year the pool was a little colder than I was used to. My warm up statics were ok but in my comp static I started shivering after about 3 minutes (contractions at around 3-3:30), which continued right up until the end, so assumably through my dive response.

Cheers,
Ben

[m2b]

I have seen the same thing as the seals this year, and it only makes sense that everyone should see it, if they look for it.

When I'm on the surface I will get to the point that I practically give in and call it a day and head for shore, quite quickly, almost after the first dive. Bad equipment doesn't help. I breathe up for the second dive and my mind tries to tell me that I can't do it. Once I submerge and start diving down I noticed that it seems like I actually do warmup. Once I get back to the top it usually only takes a matter of 15-30 seconds before I start noticing myself get cold again.

Granted this should be expected. The nature of remaining "motionless" on the surface allows both air and water to pass over the body and it helps to cool the body down. When you submerge yourself, you are "exercising" and this creates heat within the body. It only makes sense that it happens in the seals and that I notice it as well.

Now the weird thing that I have noticed this fall has been that as I get colder I seem to have a harder time getting the same quality of breath as I do when its warmer. I get in the water for the first dive and I have no trouble with the breathe up at full. I can get a nice full breathe without even working at it. It's like it's happening naturally. As I try to breathe up for the second dive I'm already getting cold, not shivering but getting cold. This time I notice that I do have an almost impossible time getting a decent breath. I've seen this happen more than once and I tend to think that it is just the body reacting to the cold environment that I have placed it in.

Next year...hopefully I won't wait as always until late August before I get in the water...I'll try some decent experimenting with the idea and see what happens. Right now I just need some warm air and water temps to work with. Guess I'll just have to wait.

Ryan

[trux]

Originally Posted by m2b

... Granted this should be expected. The nature of remaining "motionless" on the surface allows both air and water to pass over the body and it helps to cool the body down. When you submerge yourself, you are "exercising" and this creates heat within the body. ...

The article actually does not tell the seals stop shivering because they get warmer when diving. Quite oppositely - it tells they stop shivering on purpose to cool down the body temperature, hence slowing down also the metabolism and the oxygen consumption.

[Erik]

Originally Posted by trux

The article actually does not tell the seals stop shivering because they get warmer when diving. Quite oppositely - it tells they stop shivering on purpose to cool down the body temperature, hence slowing down also the metabolism and the oxygen consumption.

Yes I agree, and our perception of feeling warmer during the dive is not necessarily because we are warmer... quite the opposite I'd think. It probably goes hand-in-hand with the body's mechanism of 'cancelling' shivering while submerged.

[efattah]

In humans, CO2 build-up tends to inhibit shivering. For this reason, if you are on the edge of shivering, and you breathe-up for several minutes, you tend to 'get colder' and shiver more near the end of the breathe-up, due to lower CO2 levels.

One way around that (for hardcore cold water divers), is to do your recovery between dives in a high CO2 state (1-2 breaths per minute), then purge like crazy for 20 seconds before going down. I'd consider that a more advanced technique since the fast purging can be dangerous if you don't know yourself well.

I recently have been experimenting with certain foods & supplement combinations that are highly thermogenic, and cause your liver to really generate heat. This can allow a higher 'thermal gradient', meaning colder arms and legs with a core that is still warm.

[harbour seal]

Originally Posted by efattah

In humans, CO2 build-up tends to inhibit shivering. For this reason, if you are on the edge of shivering, and you breathe-up for several minutes, you tend to 'get colder' and shiver more near the end of the breathe-up, due to lower CO2 levels.

One way around that (for hardcore cold water divers), is to do your recovery between dives in a high CO2 state (1-2 breaths per minute), then purge like crazy for 20 seconds before going down. I'd consider that a more advanced technique since the fast purging can be dangerous if you don't know yourself well.

I recently have been experimenting with certain foods & supplement combinations that are highly thermogenic, and cause your liver to really generate heat. This can allow a higher 'thermal gradient', meaning colder arms and legs with a core that is still warm.

eric,

interesting post---thanks for the info.

could you be more specific regarding the highly thermogenic food & supplement combinations?

for cold water diving i have been using high quality fats in my diet in the preceding days. my favourite sources at the moment are flax seed (ground), avocados and hemp oil. recently i got ahold of some MCT oil, which i take 2 hours prior to diving (thanks to a previous post of yours). other suggestions would be most excellent.

cheers,
sean
vancouver, canada

[naiad]

High CO2 does reduce shivering for me, but being cold reduces my CO2 tolerance and increases the rate of CO2 production, so I soon end up with a combination of shivering and contractions.

[apneaboy]

My shivering stops on the breath up if i relax enough too, when relaxed cold feels different. Its just a sensation and my body can ignore it. Eventually i can't ignore it and i have to get out but it can be ages after i first start shivering i can stop it.

I think if you dive regularly in the cold it gets easier.

The biggest thing for me is looking after yourself on the way to the dive site (temperature of the car, what you have eaten), and at the dive site before you get in (wooley hats, lots of layers and stay out of the wind). Some days i forget all the little tricks, especially at the beginning of winter and i'm cold before i start but if you consider everything you can be ready for the cold.

[wet]

great thread! Just want to mention this non-specific stuff:

Seals lost the pili muscles, which lift the hairs in furry land mammals for warmth, and make goose pimples on humans in cold. This is different than shivering muscles.

Also, furry land mammals have subcutaneous twitching muscles under the fur, this protects against biting/stinging/sucking insects. I think these are also different than shivering muscles, but the same type as those around the eyes which can close the eyelids instantly. (Maybe this is the origin of the Fast Twitch muscle fibers that lack myoglobin?) The eye region seems to have been the source of many uniquely mammalian physical traits, like fur coats derived from from eyelashes, eccrine sweat glands from saltwater processing tear glands, oil and apocrine skin glands from eyelid anti-dehydration glands.

I think seals, dolphins, sea otters and humans all lack twitching muscles. But I don't know if our primate relatives also lost them, I don't think so. Seems to me that a hairless ape in a jungle or savanna would be in big trouble without either a fly swatting tail and/or twitching muscles, but a seashore dweller living on tropical pocket beaches in warm seawater, sunny beaches and cool caves might be alright. Sand fleas might be a problem, but lemon grass apparently keeps them away. Also, Ochre mixed with wax/oil/fat was widely used as body paint, it may have protected against UV, insects, chill, sweating before clothing was first made.

AFAICT, prehistorically, shivering would typically only occur upon surfacing and breathe-up accompanied by brief all-over sweating while backfloating in the sunlit surface water, when laying on the beach sun drying off, like in seals, and perhaps at night during sleep on cool evenings.

During the actual dives, the water surface was warm, while at depth beneath the surface thermocline, the cooler water triggered a stronger (hypothermic) MDR instead of shivering(?). I guess that shivering can't happen when in MDR acidosis and/or muscles are lactic. Not sure about this though, need to test. When I dove a bit months ago, I was shivering and shaking everywhere, thanks to the damn winds that picked up once I got in the cold water. Made for a mighty short dive, but at least I got wet.

[m2b]

I would have to agree that I have noticed a difference depending on what I do before I get into the water/to the lake. The "warmest" dive I had all season long was toward the end of the season, late last month. I had eaten about 1-1.5 hours before diving. I did drink hot water before getting into the lake. Also, I took the long way to get to the lake with the heater on full bore in the car and I was sweating a little as I got to the lake. I did notice that the cold water didn't seem as cold as I got in. I didn't notice it anywhere near as much as I normally always did otherwise. Eric F.'s tips that he mentioned on my post from earlier this fall about cold water diving are pretty much right on the money. I'm also kinda curious what kinds of foods he has trying out. Granted I'll have to wait until next fall to try them out. I decided to call it quits after the October full moon. It just doesn't sound fun diving and then getting out when the air temperature is around 40-50 degrees. Admittedly the only time I would get a chance anymore thanks to time change is on the weekends. Its dark/even colder before I ever get home from work.

Ryan