“There is a fine point where an athlete could freeze up, break down or thrive.” That is a tagline from Craft, a Swedish maker of clothing catered to runners, cross-country skiers and cyclists.

During activity or not, the average body functions best at about 98.6 degrees — no matter the temp outside. Skin temperature, sweat and moisture management affect performance. With its line of aerobic-minded apparel, including base layers, tights, and jackets, Craft touts “climate control” for a body in motion.

This winter, for running and skiing, I have been testing two Craft products. The proZERO Zip Mock Neck, $55, comes with high claims, including superior “ventilation, moisture transportation and drying time better than any other fabric technology on the market,” according to promotional text.

The secret to this base-layer top is in its fancy polyester fabric. To be precise, the company (www.craft-usa.com) refers to a “multi-channeled hollow polyester filament” that was invented to increase the release of warm body heat and moisture absorption.

I like the proZERO Zip Mock. It has a nice fit, a high collar, and a long back that tucks in and stays in place. On long runs in the cold, it wicks fine for a mile or two. But once my heart rate is high — as with every base layer I have ever tested — sweat simply soaks through the Craft fabric.

The proZERO top has a soft feel, almost like cotton. It is a little thicker than most base layers I wear. Overall, it is a quality piece, but far short of a miracle for “climate control” in cold weather.

The second Craft product, the Performance XC Storm Tights, cost about $120. They are a slick solution on extremely cold days. Wind-resistant panels and legs lined with a light fleece keep you toasty. Articulated knees and a svelte design make the tights amenable to running and cross-country skiing.

My main issue with the tights was that they were too warm. Unless it was below about 15 degrees F outdoors, my legs were hot. And this is with nothing but boxer shorts underneath.

You can use the XC Storm Tights in 10-degree weather and run fast. There are vents under origami-like folds on the knees. The front panel is wind resistant, but the back of the pant is thinner to help your legs breathe.

One day, when it was below zero in Minnesota, I ran for a few miles in the tights. A thin pair of wool long underwear and the tights provided all the warmth I needed when on the move.

On polar days when most everyone else stays inside, I pull on the Craft tights and lace some winter runners. I coax my dog out the door, his breath frosty spouts as we take off on a neighborhood run. Our legs stride together, warm enough, for a few miles on the snow.

—Stephen Regenold is founder and editor of www.gearjunkie.com.