Perspiration Can Kill You

In an interesting experiment this past week, I put the power of perspiration to the test. My son, Ryan, and I went for a 9-mile hike through a Pacific Northwest rain forest just as it was proving how it got named that way. During our 4-hour trek (much of which was on a cedar plank walkway), it was like standing under a shower head, but fully clothed.

Speaking of clothing, Ryan was wearing a loose-fitting $1.79 plastic pocket poncho over some lightweight appropriate (meaning non-cotton) outdoor clothing. On his head, beneath the poncho hood, he word a wool cap. On his feet were leather hiking boots that had been treated with waterproofing a few years ago.

I was wearing cotton sweat pants beneath a pair of waterproof foul-weather pants, a cotton long-sleeved shirt under a high-dollar waterproof shell with a hood. No cap or hat. On my feet were cotton socks and lightweight trail shoes that were mostly mesh but had solid soles with aggressive tread pattern.

So, out through the forest we went, getting thoroughly dumped on all the while. Even under the forest canopy, water fell in giant drops. Every bush was drenched and anxious to share moisture with us as we brushed past. The ground was saturated and puddles flooded parts of the trail that were not on the cedar plank boardwalk.

Ryan is taller and has a longer stride than I do; plus he's half my age, so he hikes faster than I can comfortably keep pace. In the first hour, pushing myself to keep up with Ryan, I quickly overheated and  had to open my jacket and remove the hood to keep from overheating. There went the benefit of a waterproof shell.

Without a hat, my hair was immediately drenched. And even by aggressively trying to vent the heat out of my jacket, the fast pace and exertion caused me to sweat so much that my cotton clothes were soaked. The result was that the inside of my $150 waterproof jacket was as wet as the outside. The same was true of the inside of my waterproof pants; the cotton sweats were so wet that it made me think the outer shell had failed.

Actually, the only failure was in the choice of clothing. The foul-weather jacket and pants were doing their job. But by wearing cotton against my skin, and then by exerting myself with the pace of the hike, I was able to totally negate the benefits of proper outer clothing.

Ryan, on the other hand, wearing his loose-fitting (so it vented excess heat and humidity easily) cheap plastic poncho over clothing made of synthetic fabrics, was dry. His cap kept his hair dry. His boots kept his feet fairly dry. The pace for him was ideal, so he didn't work up a sweat. He came out of the rain forest 4 hours later almost as dry as when he went in.

So here's what we learn from all this:

• Do not wear cotton clothing during cold and/or rainy weather. Merino wool is best, and synthetics run a close second. 
• Wear loose-fitting waterproof shell clothing that will allow your body to ventilate easily, permitting moisture to escape to the atmosphere rather than being trapped in your clothing. 
• Even a cheap waterproof shell is adequate if it will protect you against moisture from penetrating to your clothing. The key is not building up moisture on the inside. 
• Do not allow yourself to perspire. If you do that, you might as well not wear a waterproof outer shell. 
• Slow your pace to a comfortable work load that will minimize sweating and overheating. Even if the slower pace is going to mean a longer period of time before you reach your destination, it is better to arrive dry and late rather than on time but wet and exhausted. 

This is exactly the stuff that survival story headlines are made of. Someone goes on a short day hike, gets wet, gets tired, becomes hypothermic, and ends up in serious trouble (or worse).