https://youtu.be/VmC3-KRXDIwThere are many videos like this, I also have seen his interviews with Joe Rogan and the rest, so I'll save you the research first with a summary.
Wim goes in ice water all day for records and climbed the Himalayas with no shirt on in shorts. He has a training camp and lots of science to show we can all be cold proof. More interestingly, you connect more with your neo-cortex. My research on the subject showed Gallic warriors would have specialized fanatic divisions that would fight completely naked other than a loin cloth on frozen terrain in battles that cold be quite long, and march like that as well. This helps you to be fearless in battle and less susceptible to conscience pangs in battle, because you are completely tapped into what Jews would call the nefesh ha bahamit, the animal soul. The Nazis showed what complete dominance of this results in by trapping fathers and sons in cages for a month and then throwing in a scrap of bread, and they were incapable of resisting the urge to kill their sons for the bread. Also may the Nazis all stay in hell forever.
His blah time goes he went through a bunch of religions, and laughably connecting to his animal soul was like the apex of what he found in all the rest of them. As someone who went through the same thing it's hilarious because he's completely right, that's all I found and ice water is better. Too bad we don't have good Noachide marketing. Anyways he decided now that it's a great idea to worship cold, and his eyes betrayed him during the Joe interview that it's real idolatry and other speeches where he calls the cold his mater. This would not normally be an actual threat because it's obvious that heat can dominate cold and he clearly isn't able to relax the other way and understand the benefit of it, so his ideology and its benefits are clearly limited and there's jokes you can make to explain it. Unfortunately, he's the only one who doesn't care that he gets laughed at since his wife already left him, so he's muscling through. So they can say "well maybe it's good to worship cold since he does and he's the only one [laughable] that can sit in ice all day". There are many people even dumber than that. Also he doesn't understand that his immodesty is what causes people to laugh at him because poor bud doesn't have Torah, and if for instance he wore a thin white cloth sheet thing that was modest then the world would have to give him respectful attention.
Anyways, if you have Torah you know in your head is right but you just can't get your animal side to get it, go sit in ice water for ten minutes and explain it to him, you're connected when he's fighting, and then go in a hot sauna then bath and it's good for all kinds of things in your health. If you do it longer you get better at immune system control. For completeness' sake, to withstand heat I have no idea to teach people older than 11 years old or maybe 12 if they're special, but you start by feeling the skin under your fingernails with your focus, and the throbbing you feel and don't judge and you can feel all the blood rushing through your body, then you feel the middle bend of your middle finger, or which ever one you want, don't worry if you feel pain in the bone, that goes away when you feel it calmly because micro tears in the muscles and cracks in the bones are being healed with simple focus, and then you can feel all the bones in your hand from there and then go up your body. Then you train feeling all your blood rushing and bones for a bit. Then feel your muscles, usually people spend a while with that so no tricks needed, and get better at feeling them all with all that before. Then feel how your shirt feels against your skin, and you can feel all your exterior. When you can feel all those at once, you can ignore their constant messaging and feel the energy that isn't any of those and is the key part of you. The more you relax that the more heat will pass through you. Wim has a breathing method for cold and it's good, for heat you have to do the opposite of making everything in you fight for survival, make everything in you relax into everything around and connect to it by trying to look for where in you, you can feel the things outside of you, the more you practice the more you can feel at once. So you focus on any stress or feeling of less than serenity, push it out while breathing, and then focus on the energy that is you, and breathe that in. Constant controlled breathing does nothing, but most people's focus improves and their minds can kick in to relax their bodies so the excess energy (heat) passes through you.
Anyways it obviously needs to be said that the military applications are endless and inspiring. Soldiers that don't fear cold [and heat] are more useful in harsh environments, and it costs less in medical bills if they can regulate their immune systems with their minds. I would mention that experimenting on yourself can cause an immunocompromised-immunocompetant mixture that if the person has type one herpes will allow it to enter the brain and cause encephalitis, which is extremely annoying, so focusing on the cold resistance first so the person excels at making his immune system resist everything is critical before the heat resistance where he can open everything up. Also once as you train a person for extreme heat resistance he can't stop until he leaves, because you get a layer of skin that is the most itchy thing in history when your hands and everything peels because your body doesn't use it anymore, and I really hated that.
Anyways there's not much more to say on Wim but move around in ice water with breathing techniques designed to keep your mind fighting, and as a daily practice you should spend a bit breathing in deeply and only releasing the air that pushes out naturally with no effort, and keep intaking more air than you release, and then hold your breath as long as you can. This daily training besides increased lung capacity brings improved ability to withstand cold.
To put it with what I know, start by slapping water so it makes a nice noise but doesn't displace much water over and over all day, eventually you can hit wood forever, then stone then metal. This is for open handed hinds and pounds or karate chops. For for fist, punch sand not so much at first because the sand will penetrate skin, and after a week it doesn't, if that's too hard start with grassy earth or alot on the water. Then move up with softer to harder woods as you gain strength and then stone and metal. For the knuckles, slow gradual is much more critical as your bones can become arthritic and damaged G-d forbid, as observed with many soldiers.
Every farmboy and renovation part-timer knows little cuts on your skin are good because then you are more resistant to little cuts. This is possible without bleeding and alot of equipment, tons of cuts are made into the skin all over the body and then again and again as they heal, and the skin develops a more leathery quality that resists tearing.
As observed with Shaolin monks that withstand a dozen men ramming their abdomen with a wooden battering ram, you can improve your shock resistance. It should be said that for the case I mentioned, the person must be excellent at balancing himself as well. It really as simple as getting wacked with things, but it must be on certain parts of the muscle, wacking the bones damages them, so this shouldn't be done without monitoring.
So heat-cold resistance, along with skin tear and core shock resistance topped off with the ability to control your immune system when mastered, and you've got a nice soldier or easier life. I do recommend his training camp, you will find chochma (wisdom) but no Torah (in this case, I mean answers kinda but the real answers). I always saw beating people with sticks randomly in the middle of the night until they can beat them off as the best way to get people to activate their nefesh ha bahamit and accompanying survival instincts in an instant, but the cold is much better. Perhaps dropping hundreds of gallons of ice water into a sealed room with a sleeping soldier and making him fight off several before he can escape would be the ultimate training in that regard, and should be tested.
8888888+--To get to the next level you need visualization. I remember watching Wim win the world record for being submerged in ice on TV, and at a certain point, his body temperature decided it would go ahead and raise. The reported asked him after, and he said that he imagines his body made of logs burning on fire. It's the technique I decided I'd use over the years, and to advance there, it's not about how pretty and detailed you can imagine the log and fire, you keep the image but it's about how much you can truly believe that you are currently a burning log that will determine how much you can raise it. Sophrology can help improve these skills.