The Warmest, Most Durable Fabric for Long Underwear? Power Stretch.

December 6, 2016

Nearly 20 years. That’s how long I’ve had the Power Stretch top that I still routinely wear on cold-weather bike commutes. In my experience, there is simply no other fabric that performs as well, as warmly, or as durably for my base layer needs.

Men's Arcteryx Rho AR Zip Neck Power Stretch Top.
Men’s Arcteryx Rho AR Zip Neck Power Stretch Top.

As the name implies, Power Stretch fabric features a distinctive four-way stretch, which allows it to fit snugly against your body (a crucial element of warmth) while simultaneously allowing full and unrestricted motion. (Most other fabrics feature two-way stretch; they’ll flex in one direction but not the other.)

Power Stretch is also soft and fleecy on the inside—it feels great against the skin—but smooth on the outside, which provides a largely friction-free surface to layer over top of. The smooth surface also resists pilling, the annoying tendency of fleece to form tiny balls on the surface over time.

The stuff is extremely durable. While my long-lived Power Stretch top has thinned some over the years and lost some of its warmth, the fabric itself is essentially intact with no loose threads or unraveling to speak of.

Power Stretch isn’t cheap—expect to pay roughly $75 to $125 for a quarter-zip top or pair of bottoms—but in my experience it is money well spent, especially when you think about the cost being spread out over many, many years of use.

Like any long underwear, a Power Stretch top or bottom should fit snugly, with no loose or large air pockets, and not restrict motion in any way. For Power Stretch tops, I recommend quarter-zip versions, which give you the chance to vent if and when you start to overheat. Full-length zips are available in some models, but you’re increasing the risk of the zipper failing over time (especially at the bottom of the zipper—a common point of failure).

As you shop for warmth this coming winter season, it can be surprisingly hard to find Power Stretch garments. Here are a few of this year’s offerings that caught my eye.

Stay warm!

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Matt Heid

Equipped blogger Matt Heid is AMC's gear guru: He loves gear and he loves using it in the field. While researching several guidebooks, including AMC's Best Backpacking in New England, he has hiked thousands of miles across New England, California, and Alaska, among other wilderness destinations. He also cycles, climbs, and surfs.