If you want to learn a potentially life-saving action, you need to practice it. And if you need to learn if your clothing and other gear is capable of saving your life, you need to test it. This is how the Navy SEALs do just that for cold weather emergencies.
This article was originally written by Alex Tenenbaum for the Sitka Gear blog and is reprinted here with permission.
Go for a short walk, and you'll know if your gear fits. You might notice the stretch, the lightness, the breathability, the warmth. But you won't really know if it can keep you alive.
You could take your clothing maker's word for it. But if you're a Navy SEAL operating in frigid conditions where leaving early isn't an option, and holding your position is mission critical, you have to know exactly what your gear can handle. You have to test for yourself how it will perform in the worst possible conditions.
John Barklow photo; and top photo.
And that's why Sitka Big Game Product Manager John Barklow and his fellow Naval instructors came up with the Rewarming Drill.
John was 19 when he enlisted and formally trained as a Navy diver. He built up some experience climbing and mountaineering in his off time, and took stations in the Philippines, the southern U.S., and California. After 9/11 he ended up in Kodiak, Alaska, where he used his experience to teach SEALs how to survive like mountaineers.
For the better part of a decade, part of his job was to develop clothing systems and equipment. He tested every piece of cold weather gear available to consumers (along with a few pieces that were not) and "shook the box to see what rose to the top."
After that he consulted for a few mountaineering companies as they developed gear to keep US operators mobile, effective, and alive. And today he's here at Sitka, helping to build future generations of the Big Game line.
We knew SEALs were a different breed. A few of them have become good friends, guys we like to grab a beer with or charge hard with in sketchy terrain. But they're usually pretty quiet about their service. So when John told us about the training he put these guys through, in particular the Rewarming Drill, it was the first we'd heard of it. We just about fell out of our chairs.
"It was meant to mimic the scenarios you hope to never encounter," John says. "Maybe you fall in a river, or a rain storm catches you without your Gore-Tex, or you push too hard with the wrong layers and you sweat out -- however it happens, you get soaked to the bone. The deal is, if you spend enough time out there, you're going to get wet on a brutally cold day. And how are you going to keep warm? How are you going to get everything dry and keep going?"
The exercise went like this: After a three-hour patrol into Kodiak's interior, usually with a storm seething in off the Pacific, John would funnel the troops into a clearing. Only it wasn't a clearing. It was the surface of a half frozen lake.
"Alright!" John would say, his voice cutting through wind and freezing rain. "This is the Rewarming Drill!"
The troops would drop their packs on the shore and march ahead fully clothed until they were neck deep in frigid water. For 12 minutes they shivered until John gave the order. With their clothes sopping, violently shaking, they emerged from the cold lake into colder air.
Just hit pause for a second. Say you got soaked on a hunt. What would you do next? What steps would you take to get warm?
If you're like most of us, you'd probably build a fire, strip off your wet layers, and try to dry them out over the flames. Except remember that it's sleeting, and the wind is ripping. Even in good weather, you'd be riding that line between drying and burning your gear while exposing your skin to the elements.
"Getting immediately out of the elements and gaining control of the situation is imperative," John says.
So here's how John taught the SEALs to handle it: The soaking, shivering troops partnered up, stumbled to their packs, and pulled synthetic insulation layers over their drenched base layers and soft shells. One set up the tent while the other got out the stove to melt snow and heat water. Then both men crawled into their tents, into their synthetic sleeping bags, and lied there shivering, waiting for water to boil outside. As soon as they could, they'd sip hot drinks and scoop spoonfuls of rehydrated chilli into their quivering mouths, and then lie back down. There in the tent, the hot food stoked their metabolism, warmth crept slowly back into their extremities, and they were no longer shivering. After several hours, they were warm and completely comfortable, with dry base layers, slightly damp mid layers, and heavy frost collecting on the exposed sleeves of their puffy jackets -- proof that their clothing system was pushing moisture to the exterior.
It worked because the human body puts out a serious amount of heat, and because the operators were using a carefully chosen combination of moisture-wicking synthetic base layers, warm-when-wet insulation (not down), and warm-when-wet sleeping bags -- along with well ventilated tents. The humans themselves were the heat source that heated the moisture, converting liquid water to water vapour, and each piece worked together to push the expanding vapour out of the system.
"With a great clothing system there's no need to carry extra layers," John says. "It should be able to perform as a symbiotic system in the most uncompromising situations. Taking off your clothes and hanging them in your tent is ineffective at best, and requires you to carry more than is required."
It's important to note that a single wrong piece would have greatly reduced the system's effectiveness. Since cotton is hydrophilic, cotton boxers would have held moisture and slowed both the drying and rewarming times. Down also retains moisture, and fails to insulate when wet, so a down puffy or sleeping bag would have made for disastrous results.
"Most people don't believe it works at first," John says. "We did it with some industry folks once, and they didn't really believe it. These were the guys developing our military gear. They'd never heard of this before or done anything like it. And it's like, 'Well how do you know if your stuff even works?'"
But John didn't leave it there. Since troops wouldn't always have their tent, sleeping bag and stove with them, he drilled his operators without them -- and in colder weather. He called it the Dynamic Rewarming Drill.
Similar to the static version, the operators cut holes in thick Kodiak ice, treaded water for 12 minutes, climbed out, and pulled on their synthetic puffy layers. But now, instead of making camp John had them shoulder their packs and march, moving at a slow, easy pace -- fast enough to generate heat to cook their layers, but not so fast that they'd sweat and create more moisture. Within an hour of walking, their base and mid layers were dry. Two hours later, when they marched into camp, they pitched tents, unfurled their sleeping bags and crawled inside, heating water and rehydrating food to stoke their metabolism and complete the drying process.
"The point of these exercises is knowing what your systems are capable of and gaining experience and confidence in them. Knowing that these systems will work frees you to focus your attention on hunting." John says. "But don't take anybody else's word for it. Try it for yourself. And remember -- it doesn't have to be fun to be fun."
Every Rewarming Drill John ran had the benefit of trained medical observers, as well as fire extinguishers and other key safety equipment. So DO NOT cut a hole in the ice and jump in without taking the same precautions. If you want to test your gear at home, go with the ice bucket challenge. On a chilly day, soak your current system in a bucket of ice water, wring it out, and put it on. Then follow the rewarming steps above. You'll very quickly identify any weak points in your system, and you'll know whether your gear can handle it.