There are few things that kill a runner's high faster than the moment when hot and sweaty turns to cold and clammy.
On too many occasions, I've assumed that the T-shirt I wear in warmer weather or on the treadmill will get me through a winter weekend jog. Big mistake.
So I stepped into the Running Room recently in search of a better base layer and the salesperson directed me toward Mizuno's Breath Thermo range. Apparently, the fabric warms up when exposed to moisture. She anticipated my skepticism and pulled out a little package containing a sample of the fibre and a doll-sized squeeze bottle filled with water. Sure enough, the moistened material heated up in seconds.
But a cool demo is not the same as a real-life run. Mostly, I wondered whether the long-sleeve top would leave me warm and wet, only marginally better than shivery cold.
I tried a crew neck top that features alternating panels of thick and thin Breath Thermo fabric, strategically placed under the arms and along the side body, across the shoulder blades and toward the forearms.
It occurred to me as I shifted from jog to walk that that the warming sensation wasn't nearly as pronounced in the wearable material as the store demo.
Barbara Mitchell, the marketing manager for Mizuno in Canada, explained that the sample is 100-per-cent Breath Thermo whereas the garments contain anywhere from 7- to 13-per-cent of the fibre. This is a good thing, as anything more and I'd probably melt.
She helped me understand that the technology exists within the fabric, not as a coating or treatment. First developed in Japan decades ago (and introduced to Canada during the Vancouver Olympics last year), it works by trapping the body's moisture, which in turn activates the fibre's molecules. As they rub together, they give off heat, warming the surface to a maximum two or three degrees Celsius.
Unlike other wicking materials, this poly-blend doesn't get smelly (it's deodorizing). But it doesn't eliminate moisture entirely. You'll still feel dampness, as I did when testing the cap and gloves. It's a less uncomfortable dampness, though.
Ms. Mitchell says that all the alternating fabric weights are designed to support the muscles and ligaments. That's good to know but would not be my primary reason for choosing Breath Thermo (the line ranges from $15.99 to $139.99).
I like that the heat feature won't fade over time and that it generally makes for a more temperature-controlled experience. I'm looking forward to warmer weather but until then, at least I have my warming shirt.