WEBVTT - How Can Your Body Learn to Tolerate Cold? 0:00:01.840 --> 0:00:08.320 Welcome to Brainstuff, a production of iHeartRadio. Hey Brainstuff. Lauren Vogelbaum. 0:00:08.440 --> 0:00:13.080 Here picture a brisk morning at the sandy shore of 0:00:13.119 --> 0:00:17.960 San Francisco Bay. Tony Gilbert is not a former Olympian swimmer. 0:00:18.320 --> 0:00:20.919 He's not part of a super athlete team, though he 0:00:21.079 --> 0:00:24.599 knows swimmers like that, and he's not wearing a wetsuit. 0:00:25.640 --> 0:00:28.920 In his usual swim trunk, swim cap, earplugs and goggles, 0:00:29.160 --> 0:00:32.800 Gilbert wades into the forty six degree fahrenheit water that's 0:00:32.880 --> 0:00:37.520 seven degrees celsius, and swims out into the murky Bay. 0:00:37.680 --> 0:00:41.240 Gilbert is a hobby cold water swimmer. He's been doing 0:00:41.240 --> 0:00:44.120 it for over a decade. He returns to shore some 0:00:44.159 --> 0:00:49.120 forty minutes later, exhilarated for the article. This episode is 0:00:49.120 --> 0:00:51.440 based on haws toff Work spoke with Gilbert back in 0:00:51.440 --> 0:00:55.840 twenty twenty two. He said, it's really cold, but we 0:00:55.880 --> 0:00:59.040 wouldn't do it if it wasn't fun. It's invigorating. Really. 0:00:59.400 --> 0:01:01.840 The first few minutes are still the worst. Then you 0:01:01.920 --> 0:01:04.920 get going, the endorphins kick in and you love it. 0:01:07.160 --> 0:01:09.280 Gilbert is one of the members of the South End 0:01:09.360 --> 0:01:13.560 Rowing Club, founded in eighteen seventy three. Who regularly take 0:01:13.600 --> 0:01:18.000 dips in the frigid bay for fun. Gilbert's swims usually 0:01:18.120 --> 0:01:20.600 range from twenty to forty minutes, but he's gone as 0:01:20.600 --> 0:01:24.880 long as ninety minutes. The curious onlookers might wonder how 0:01:24.880 --> 0:01:29.320 he doesn't experience hypothermia or why he actually enjoys swimming 0:01:29.400 --> 0:01:33.800 in such cold waters. It turns out that the human 0:01:33.840 --> 0:01:37.120 body has evolved some pretty helpful tools to acclimate two 0:01:37.200 --> 0:01:42.280 different kinds of cold stress when necessary, depending on the frequency, duration, 0:01:42.520 --> 0:01:47.480 and severity of the cold experienced. Basically, when we need 0:01:47.520 --> 0:01:51.320 to move around and be comfortable in non life threatening 0:01:51.400 --> 0:01:56.400 chili conditions, our bodies can habituate to the cold. When 0:01:56.400 --> 0:01:58.840 the cold gets a little more serious, we can go 0:01:58.920 --> 0:02:04.160 through more intense adaptations. To talk about all this, first, 0:02:04.280 --> 0:02:06.640 let's go over how your body tries to protect you 0:02:06.800 --> 0:02:12.399 when you experience cold. Okay, human beings are warm blooded mammals, 0:02:12.639 --> 0:02:16.440 which means that we thermoregulate to keep a stable internal 0:02:16.440 --> 0:02:20.280 body temperature, usually a little warmer than our environment at 0:02:20.280 --> 0:02:24.680 which our organs and systems function well. For most humans, 0:02:24.800 --> 0:02:28.600 that internal or core body temperature is right around ninety 0:02:28.600 --> 0:02:31.679 seven to ninety nine degrees fahrenheit, which is thirty six 0:02:31.720 --> 0:02:36.040 point one to thirty seven point two celsius. We are 0:02:36.120 --> 0:02:39.760 able to stay right at that temperature because well, a 0:02:40.040 --> 0:02:44.320 we've invented things like clothes, but b our digestive system 0:02:44.400 --> 0:02:48.040 and cells break down the food we eat and metabolize 0:02:48.040 --> 0:02:50.560 the glucose in it into a compound that our cells 0:02:50.639 --> 0:02:54.880 can use for energy called adenisine triphosphate or ATP, and 0:02:55.000 --> 0:02:59.520 heat is a byproduct. When you get too cold, like 0:02:59.560 --> 0:03:03.200 your body temperature drops below ninety five degrees fahrenheit or 0:03:03.240 --> 0:03:07.000 thirty five celsius, your organs can't function and begin to 0:03:07.000 --> 0:03:12.239 shut down, which is bad. This is the aforementioned hypothermia, 0:03:12.520 --> 0:03:16.280 and it can kill you. So when your body detects 0:03:16.280 --> 0:03:19.160 a drop in temperature, it has a few defensive measures 0:03:19.200 --> 0:03:23.960 it'll take to keep your core warm. You might start shivering. 0:03:24.680 --> 0:03:28.160 This is an involuntary type of muscle contractions that start 0:03:28.160 --> 0:03:32.040 in the torso and move to the limbs. What's happening 0:03:32.080 --> 0:03:35.480 here is your body is attempting to create more internal heat. 0:03:36.720 --> 0:03:40.040 Your muscles produce some heat whenever they contract through a 0:03:40.280 --> 0:03:44.040 complicated biomechanical process that I don't understand very well. But 0:03:44.480 --> 0:03:47.080 this is why moving around can help you warm up. 0:03:48.280 --> 0:03:53.000 But more importantly for shivering, those repeated and rapid contractions 0:03:53.240 --> 0:03:57.600 use up ATP real fast, prompting your cells to metabolize 0:03:57.600 --> 0:04:02.200 more glucose into ATP plus heat. Of course, your skin 0:04:02.280 --> 0:04:04.400 is one of the first line systems that your body 0:04:04.440 --> 0:04:06.680 has to sense the cold, and it has a couple 0:04:06.680 --> 0:04:10.480 of tricks to pull too. It might go over in goosebumps, 0:04:10.640 --> 0:04:14.320 which is another type of involuntary muscle contraction, but instead 0:04:14.360 --> 0:04:17.880 of big muscles giving you big shivers, these are tiny 0:04:17.960 --> 0:04:20.640 muscles contracting in your skin to generate a bit of 0:04:20.680 --> 0:04:24.000 heat and raise up your hair follicles, thus trapping a 0:04:24.000 --> 0:04:26.280 bit of air near the skin and thus holding on 0:04:26.360 --> 0:04:29.800 to a little bit of body heat. This might have 0:04:29.839 --> 0:04:32.479 a negligible effect in humans and work out better for 0:04:32.520 --> 0:04:36.560 our furrier cousins. But your skin can also perform another 0:04:36.600 --> 0:04:43.080 involuntary function called cutaneous vasoconstriction. That means vascular constriction in 0:04:43.120 --> 0:04:47.120 your skin. That is, your blood vessels contract, letting less 0:04:47.160 --> 0:04:51.000 blood flow through them at your skin level. You shed 0:04:51.040 --> 0:04:53.880 heat through your skin, and especially via blood flowing close 0:04:53.920 --> 0:04:58.560 to skin level, so cutaneous vaso constriction keeps that blood 0:04:58.720 --> 0:05:01.760 and thus that heat closer into your core to keep 0:05:01.800 --> 0:05:05.839 your inner organs warm. This is why your extremities your 0:05:05.920 --> 0:05:09.280 hands and feet get cold the fastest in chili conditions. 0:05:09.640 --> 0:05:12.080 Your body is trying to keep its heat towards your core. 0:05:13.920 --> 0:05:16.960 In these our modern times, we tend to moderate the 0:05:17.000 --> 0:05:19.800 amount of cold that we're exposed to by bundling up 0:05:20.000 --> 0:05:24.200 and spending more time in heated indoor areas. But even 0:05:24.240 --> 0:05:27.400 when we only dip into cold temperatures briefly, even with 0:05:27.480 --> 0:05:31.400 a minimum of skin exposed, our bodies can habituate to it. 0:05:32.480 --> 0:05:35.960 We experience habituation, for example, over the course of several 0:05:36.040 --> 0:05:39.400 cold mornings during ten minute dashes out for coffee or 0:05:39.480 --> 0:05:45.280 to walk the dog. Habituations are like physical memory. Instead 0:05:45.320 --> 0:05:48.760 of wasting valuable bodily energy sending up red flags to 0:05:48.800 --> 0:05:51.480 your central nervous system. Every time your body is exposed 0:05:51.560 --> 0:05:55.239 to a cold event, your body remembers it and responds less. 0:05:55.360 --> 0:05:59.640 Over time, you won't shiver as much, and your skin 0:05:59.680 --> 0:06:03.000 and extras will stay warmer for longer because your body 0:06:03.040 --> 0:06:08.599 won't immediately draw blood inward to protect those vital organs. Basically, 0:06:08.760 --> 0:06:11.840 your body realizes that the cold isn't going to seriously 0:06:11.920 --> 0:06:15.240 damage you and that's also not going away, so it 0:06:15.279 --> 0:06:18.000 adjusts to let you function better in the midst of it. 0:06:19.160 --> 0:06:21.320 And it's a lot easier to function when you're not 0:06:21.400 --> 0:06:25.919 shivering and your fingers aren't numb. This is how cold 0:06:25.960 --> 0:06:30.040 water swimmers can tolerate near freezing water. They habituate to it, 0:06:31.240 --> 0:06:33.960 but a swimmer can't adjust to swimming long lengths and 0:06:34.040 --> 0:06:38.599 cold waters on their first trip. Gilbert said, you have 0:06:38.680 --> 0:06:42.240 to be regular, consistent with cold water swimming to stay acclimated. 0:06:42.720 --> 0:06:44.400 You have to swim two to three days a week 0:06:44.440 --> 0:06:47.160 to stay acclimated, and the few times I did have 0:06:47.200 --> 0:06:49.520 a break or fall off schedule, I would start back 0:06:49.560 --> 0:06:52.279 at square one. Start with a short ten minute swim 0:06:52.320 --> 0:06:55.479 one day, and then the next day try fifteen twenty, 0:06:55.720 --> 0:07:00.679 and then back to thirty or forty five minutes. Even 0:07:00.839 --> 0:07:03.880 the best, most adjusted swimmers get too cold and have 0:07:04.000 --> 0:07:07.479 to stop when their body tells them it's time. Gilbert said, 0:07:07.880 --> 0:07:10.800 your body keeps warm at the core, so your extremities 0:07:10.840 --> 0:07:15.160 can get cold, especially your fingers are toes. On longer swims, 0:07:15.240 --> 0:07:17.680 you'll even see some people get a claw hand or 0:07:17.800 --> 0:07:19.760 some people get numb in the lips for a few 0:07:19.800 --> 0:07:21.880 minutes and slur their words when they get out of 0:07:21.920 --> 0:07:26.480 the water. This, by the way, is part of why 0:07:26.520 --> 0:07:29.760 cold water swimmers swim with buddies of form clubs and 0:07:29.880 --> 0:07:33.520 enlist more experienced swimmers to help teach new hobbyists how 0:07:33.520 --> 0:07:37.600 to stay safe. If you're interested, definitely look into organizations 0:07:37.640 --> 0:07:42.440 in your area. Anyway, Over the past couple of decades, 0:07:42.560 --> 0:07:45.520 researchers have been looking into another way that our bodies 0:07:45.560 --> 0:07:49.240 protect us from the cold. It turns out that shivering 0:07:49.360 --> 0:07:51.840 is not the only cold induced way that our bodies 0:07:51.920 --> 0:07:58.360 have of producing heat to warm us up. Enter brown fat. Now, 0:07:58.720 --> 0:08:01.640 body fat in general is a good insulator and can 0:08:01.680 --> 0:08:04.720 help your core stay warm, but there are different kinds 0:08:04.720 --> 0:08:09.720 of body fat, white, brown, and beige. A white fat 0:08:09.760 --> 0:08:12.120 is the kind you probably think of when you think 0:08:12.160 --> 0:08:14.880 of body fat. It's made up of cells that store 0:08:14.920 --> 0:08:18.320 lipids to cushion and insulate our innerds and to save 0:08:18.360 --> 0:08:22.400 potential energy for a rainy day. It's creamy white in 0:08:22.520 --> 0:08:26.280 color because each cell is basically just an envelope of lipids, 0:08:26.400 --> 0:08:30.520 with the cells operative equipment the nucleus and mitochondria squished 0:08:30.520 --> 0:08:34.120 out to the sides. Brown and beige fat are so 0:08:34.240 --> 0:08:37.760 named because they contain a lot more rusty colored, iron 0:08:37.840 --> 0:08:41.600 rich mitochondria at giving the cells a brown or beige color. 0:08:42.840 --> 0:08:47.079 When you regularly experience cold, your body starts to activate 0:08:47.160 --> 0:08:50.440 brown and beige fat cells to basically burn their lipid 0:08:50.480 --> 0:08:55.320 stores in order to produce heat. For the article, this 0:08:55.360 --> 0:08:57.760 episode is based on how stuff Works. Spoke with Te 0:08:57.840 --> 0:09:01.480 Chung Lin, a PhD and Associate professor of biomedical research 0:09:01.520 --> 0:09:06.319 at the Masonic Medical Research Institute. He said brown fat 0:09:06.400 --> 0:09:09.240 serves as a fireplace in our body to keep us warm. 0:09:09.720 --> 0:09:13.880 Individuals regularly exposed to cold, such as winter swimmers, have 0:09:14.040 --> 0:09:21.200 higher heat generation efficiency than normal healthy individuals. Some scientists 0:09:21.320 --> 0:09:24.240 argue that brown fat evolved early on in mammals and 0:09:24.360 --> 0:09:28.079 helped give us a leg up from other species. Human 0:09:28.120 --> 0:09:30.400 babies are born with a lot of brown fat to 0:09:30.480 --> 0:09:34.280 protect them from cold at birth. Adults tend to retain 0:09:34.400 --> 0:09:37.520 a little brown fat stored mostly between our shoulder blades. 0:09:38.720 --> 0:09:42.800 Beige fat cells, meanwhile, seem to arise within populations of 0:09:42.840 --> 0:09:46.640 white fat cells due to things like cold stress, and 0:09:46.920 --> 0:09:50.080 then go about burning off their stored energy to help 0:09:50.160 --> 0:09:54.520 keep the body warm. Researchers are still looking into how 0:09:54.600 --> 0:09:57.640 brown and beige fat work and how they might be 0:09:57.679 --> 0:10:00.800 connected to health factors like blood press usure and blood 0:10:00.840 --> 0:10:05.560 sugar regulation. There's a hope that if we could figure 0:10:05.600 --> 0:10:08.280 out how to boost the action of these fats, it 0:10:08.440 --> 0:10:13.560 might help keep people healthier. So maybe those coldwater swimmers 0:10:13.600 --> 0:10:18.400 are onto something. Gilbert said, coldwater swimming feels like you're 0:10:18.440 --> 0:10:21.680 taking a bite out of life. There's nothing else like it. 0:10:26.520 --> 0:10:29.560 Today's episode is based on the article can our Bodies 0:10:29.679 --> 0:10:32.880 Learn to withstand frigid Temperatures? On how stuff works dot com, 0:10:32.920 --> 0:10:36.360 written by Alison Troutner. Brain Stuff is production of iHeartRadio 0:10:36.440 --> 0:10:38.480 in partnership with how Stuffworks dot Com, and it is 0:10:38.520 --> 0:10:41.600 produced by Tyler Klin. Four more podcasts from my heart 0:10:41.679 --> 0:10:45.400 Radio visit the iHeartRadio app, Apple Podcasts, or wherever you 0:10:45.400 --> 0:10:57.240 listen to your favorite shows.