The world's most in-depth and scientific reviews of outdoor gear

How We Tested Long Underwear for Women

By Amber King ⋅ Senior Review Editor
Tuesday November 20, 2018

Testing Process


We spent the last few months really pushing the limits of each base layer bottom. We hiked, climbed, ran, slept, and skied in each piece. We took them from the high mountains of Colorado to the cold oceans of the North Sea. Below we outline what we specifically did to evaluate each metric.

Testing Metrics


Testing Warmth

We carefully observed and researched the fabric thickness and makeup of each pair of long underwear bottoms. In addition to simple observations, we put ourselves outside when it got cold. We tested throughout the Fall season, setting up camp outside as much as possible. We endured sub-zero temperatures and hiked uphill whenever we could see our breath. Also, we busted our buns to the point of perspiration and then just sat to see which pair of long underwear kept us warm. Both when in motion and when standing still.

We explore the glaciers of Alaska while sleeping in the snow to see how warm base layers truly are.
We explore the glaciers of Alaska while sleeping in the snow to see how warm base layers truly are.

Testing Comfort and Fit

To look at comfort we observed the comparative fabric softness and thickness of each product. We touched them, wore them against our skin for numerous days on end, and noted which felt the most comfortable, when dry and wet. In addition, we determined which just felt the most comfortable to wear all day.

We look at the overall comforts here. We look to see how the fabric stretches and conforms to the body  as well as how comfortable it is to sleep in. Here we sleep out in the canyons surrounding Las Vegas.
We look at the overall comforts here. We look to see how the fabric stretches and conforms to the body, as well as how comfortable it is to sleep in. Here we sleep out in the canyons surrounding Las Vegas.

To look at fit, we had several different women of all shapes and sizes try on the different pieces. We noted relative leg lengths, the elasticity of the hems around the calf and around the waist. We also looked at the fabrics to see if it stretched after running around in the woods for a few hours…or if it retained its shape. Using these tests we are able to provide good recommendations for fit.

Since fit is so subjective, we evaluated and rated comfort in this metric. It's here that we provide fit advice.

Testing Breathability and Drying Speed

To test breathability and drying speed, we performed a few tests. First, we ran and hiked in every article, both with and without additional layers. This provided us with excellent data on which products wicked and allowed water to move through the fabric. Second, we looked at the porosity of the material to determine which allowed wind to cut right through, providing great evaporation of moisture. Lastly, we performed an in-lab dryer test. In this test, we weighed the dry weight (oz) of each product. Then we dunked each underwater for one minute to simulate the pieces getting drenched in a downpour. This allowed us to see how much each absorbed. After that, we put each article in the dryer for 10-minute increments, weighing each along the way. We stopped the test when the product got back to its dry weight. This allowed us to calculate the rate at which each piece dries…providing an objective metric.

Here we set up for our breathability  water resistance  and drying tests.
Here we set up for our breathability, water resistance, and drying tests.

Testing Durability

To test durability we evaluated the craftsmanship and construction of each piece, noting if there was any pilling to stitching fly-aways throughout the testing period. Also, to go above and beyond, we wore each piece on its own and under several layers. We noted if there was an area of high abrasion or even holes that developed in our testing period. Also, we indicate if any holes became namely apparent in the fabric after just a minor snag. To that point, we must note that long underwear is not designed to be worn on its own, but with another thicker, more durable overlayer. These tests just allowed us to see which fabrics were more fragile than others.

After use (both alone and with a layered system) we evaluate the relative durability of all fabrics. While long underwear is not meant to be worn on its own  some bottoms are more durable than others. Here we see a hole as a result of crack climbing in Indian Creek on fall afternoon.
After use (both alone and with a layered system) we evaluate the relative durability of all fabrics. While long underwear is not meant to be worn on its own, some bottoms are more durable than others. Here we see a hole as a result of crack climbing in Indian Creek on fall afternoon.