Physiology of Cold

Sandy beach run in San Francisco — almost like real training

Today I headed out to Stanford University to give a video interview about physiological responses in cold-weather endurance events. Beat and I were both recruited to give some experiential insight for an online class called "Your Body and the World: Adapting to your next big adventure." My kind of class! The instructor, Dr. Anne Friedlander, has been conducting all kinds of research into exercise physiology in extreme conditions — dunking her TAs in an ice bath, having them exercise in heated rooms. Like I said, my kind of class. 

Dr. Friedlander also is interested in having me be a guinea pig for her scientific research, toting a core temperature reader and heart rate monitor in the Iditarod Invitational. I really want to do this; I hope it works out. I've long hoped that more scientific research would focus directly on ultra-endurance sports — it's fantastic that Stanford is involved, and I'd love to be involved as well. Beat was unable to attend the interview so I had to hold down the fort. I was really nervous, so I made a few notes based on some practice questions she sent me. The interview went well I think, and my notes provide a bit of an intro into something people often question me about — "Why do you like cold-weather racing so much?"

1. It sounds like you didn’t even ride a bike until your early 20s; how did you get into ultra-endurance bike adventures? 

I started hiking as a teenager, and did quite a bit of hiking and backpacking as a youth. Around age 22 I picked up cycling because I wanted to try touring, or traveling by bicycle, and found that I loved the simplicity and ease of movement on a bike. When I was 26 I moved to Homer, Alaska, to work for a newspaper. We moved there in September and I realized that if I didn't pick up a cold-weather outdoor hobby, I was probably going to go crazy during the long, dark winter. I considered skiing, but then I discovered that some cyclists up in Alaska rode throughout the winter, on snow-covered trails. Shortly after that, I learned about the Susitna 100, a 100-mile endurance race on the Iditarod Trail. At the time I wasn't really an athlete; I didn't train and had never competed in a race of any sort. But for reasons still unknown to me, the Susitna 100 captured my imagination. Everyone who knew me thought I was nuts to jump into an event like that off the couch, but suddenly I had this wonderful excuse to go out for bike rides at night, in blizzards, at 10 below. Every day was a new adventure. I loved it. The race itself was unbelievably difficult. Trails were soft, and then it rained, which turned everything to slush, and I couldn't ride my bike at all. I was walking, I was soaking wet, and it was still 33 degrees outside, not warm. I was borderline hypothermic for hours, pushing and shivering, wavering between wanting to hit a panic button and just sitting in the snow and giving up on life. But I made it. I finished in 25 hours. It was the worst thing I had ever done to myself, and at the finish line I announced "never again." But I was smiling. And, of course, I was hooked.

2. Why are you so drawn to races in the cold?

This probably sounds insincere from someone who chooses to live in one of the friendliest climates in the United States, but cold weather is my favorite weather. There's something magical about the subzero range; the air is often so clear that far horizons become visible, details appear sharper, the low angle of the winter sun casts the world in golden light, and snow sparkles like a sea of shattered glass. When there's no wind, a deep quiet settles over the land, and any sound becomes crystal clear. Sometimes in subzero temperatures, I can stop on a wide-open plain and hear footsteps from an animal that I can't see — something that's probably a half mile away, but sounds like it's walking beside me. Also below zero, ice crystals in the air make a tingling sound, like tiny bells. It's such a beautiful, surreal setting. There's also a life-affirming value to extreme cold — it's a death-like environment, and yet I am very much alive, moving freely in my own self-contained bubble of warmth and life. 

3.  What are the primary things you need to consider when racing in the cold as opposed to “normal” ultra-endurance racing?

Your primary consideration is regulating core temperature. You of course don't want to let your body temperature drop into hypothermic ranges, but you have to avoid overheating as well. During strenuous exercise you output a lot of heat, even in extreme cold, but at the same time you have to wear insulating clothing to keep your skin and extremities from cooling too much. The result is that you're going to sweat, and if you don't vent the moisture, it will collect in your clothing and freeze, diminishing the insulating properties and turning your body into a human snow-making machine. Having a system that's too well ventilated, or too light in insulation, can be dangerous as well, as you will burn up a lot of energy making heat while increasing your risk of frostbite. Finding that balance is extremely difficult, especially over extended periods of time. I've played with a lot of different gear set-ups and found that, at the end of a long day, my base layers end up soaked no matter what I try. So I opt for a "warm when damp and windproof" system of synthetic layers and Gortex, and carry a big down parka for instances when I need to stop moving for more than a minute or two. 

4.  What do you notice about your performance and physiology when racing in the cold?

The first thing I notice is how directly temperature affects my speed — the colder it is, the slower I move even when I feel like I'm expending the same effort. I suspect this happens because muscles never fully warm up — like an old car engine sputtering down the street on a frosty morning. Subzero temperatures definitely diminish my performance no matter how good my gear is. But at the same time, this adds to the challenge and thus the intrigue. 

5. What are some of the scariest situations you’ve been in during these cold adventures?

During the 2009 Iditarod Invitational, while crossing a frozen lake just 25 miles in, I punched through some thin ice and dunked my right leg almost to my hip joint. At the time it was about zero degrees with a strong wind, and the temperature was plummeting. I opted to get off the lake and into tree shelter to deal with my wet boot, but by the time I got there, my whole leg was encased in ice. So I made a second poor decision to continue onto the first checkpoint, which was still 30 miles away. The snow was soft and travel was slow. I would ride 10 minutes and run for 2 or 3 in an effort to keep my feet warm, but temperatures dropped down to 35 or 40 below according to others who were out there. When I reached the checkpoint, all of the ice in my boot was frozen solid with my foot inside. By the time enough ice finally melted to get my foot out, my right foot was chalk white. Rewarming my foot was one of the most painful experiences I've ever endured, and afterward blisters and black spots formed on all of my toes. I had to drop from the race, and it took several months to recover from frostbite. I still have nerve damage from that, five years later. 

There were times that I bivied in the snow, when I was so tired and the air was so cold that I felt deep and terrifying anxiety that I would fall asleep and never wake up. But the single scariest moment was perhaps during the 2011 Susitna 100, which Beat and I ran together, on foot. Temperatures had been cold all day, probably never warmer than 5 below, but we were running fairly hard and were dressed very light. When the sun set, temperatures plummeted and the wind really started cranking. We turned onto the Susitna River to face a full blast of wind and a chill that later was estimated at 50 below. I went from feeling comfortable to desperately cold in a matter of minutes, and still I waited just a few minutes too long before I finally stopped to dig my down coat out of my sled. Those few stalled minutes were enough to send my core temperature into a nose dive. I'd removed my mittens to grab my coat, and my hands froze almost immediately. They were rigid, like a claw, and useless. I got my coat on, but couldn't zip it up. I felt very cold and I was nearing panic. Beat was there and helped me zip up my coat. If I had been alone, things would have probably gotten worse before they got better. It was an important reminder about how quickly one's condition can change out there. You really have to stay on top of every little thing. 

6. What drives you to keep pushing your limits and putting yourself at risk in these ways?

I relish in the experience of being alive, and nothing makes me feel more intensely alive than seeking the edge of livability and peering out into the void. Pushing my body to its limits in a cold environment, a place where there is no margin for error, has an intensity of experience that makes it seem as though I've lived a lifetime in a matter of days. When I emerge on the other side, it feels like years have passed and I've changed and grown as a person. At the same time, I relish in the simplicity that endurance racing evokes. Like anyone, I have my petty worries, my irrational fears, my pessimistic world views and my existential despair. A hard endurance effort strips all of that excess away, exposing the basic core of who I am. By necessity, I have to let the abstract thoughts go and focus on the immediate. What will I eat? Where will I sleep? How will I get through this storm? I revert to a basic animal state, which is not only liberating, but also casts a brighter light on the parts of life that are truly important to me. 

7. What adventures or races do you have planned for the future?  Or what’s on your bucket list for that matter?

Well, of course the 350-mile Iditarod Trail Invitational in February, which I plan to race with or near Beat on foot. And beyond that — I'd love to do some winter bike touring in remote locations. Greenland, Iceland, Finland, and Baffin Island are all on my wish list. I'd love to visit Antarctica. I don't need to bike there or go to the South Pole — I'm not sure I would enjoy an expedition of that length — but just experiencing Antarctica would be a dream. And then, of course, the 1,000-mile ride to Nome. Beat thinks I should go this year, but I'm not ready. I need to gain more fresh experience first. I haven't lived in Alaska for three years, and I'm definitely getting rusty on the whole cold-weather endurance thing.