Reviews You Can Rely On

How We Tested Long Underwear for Women

Tuesday November 22, 2022

We spent months really pushing our limits while testing each pair of long underwear. We hiked, climbed, ran, slept, biked, and skied in each garment. We took them from the high mountains of Colorado and the Eastern Sierra to the cold oceans of the North Sea. Below we outline considerations that went into evaluating each metric.


We carefully observed and researched the fabric and makeup of each pair of long underwear, including fabric weight and gauge. In addition to simple observations, we braved the elements in these undies when it got cold. We tested extensively while living out of a truck in Yosemite Valley and Indian Creek. We even endured sub-zero temperatures and hiked uphill whenever we could see our breath. Ultimately we busted our buns to the point of sweat and then just sat around to see which pair of long underwear kept us the warmest while in motion or standing still.

long underwear womens - we explore the glaciers of alaska while sleeping in the snow to see...
We explore the glaciers of Alaska while sleeping in the snow to see how warm base layers truly are.
Credit: Amber King


We performed a few different tests in order to assess breathability. First up, we took each pair on a one-hour trail run to objectively measure which products successfully wicked moisture away from our skin and released the moisture through the fabric. If any fabric retained moisture, we noted the amount of time each layer required to dry, in addition to which layers were able to dry on the body. Finally, we evaluated the porosity of the material, recording which fabric allowed the wind to cut right through to provide ample evaporation.

long underwear womens - the stripped down design doesn't feature any venting for moisture to...
The stripped down design doesn't feature any venting for moisture to escape so we don't recommend the Inversion Leggings for the warmer months, however, the thick Merino fabric performed quite well when the temperatures dropped.
Credit: Trish Matheny

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. We slept in each pair of long johns, noting which garments were soft and cozy in comparison to some garments that caused irritation and itching.

long underwear womens - we look at the overall comforts here. we look to see how the fabric...
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.
Credit: Amber King

To look at fit, we had several different women of all shapes and sizes try on the different layers. We noted relative leg lengths and the elasticity of the hems around the calf and the waist. We also looked at the fabrics to see if they stretched or had enough structure to maintain their shape after several adventures between washes. We noted the effectiveness of the waistband and whether or not it provided structure without decreasing comfort. Finally, we noted which garments fit true or size and which ones felt necessary to size up or down. After performing these tests, we are able to provide accurate recommendations for comfort and fit.


To test durability, we evaluated the craftsmanship and construction of each piece, noting if there were any pilling or stitching flyaways 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 holes that developed during our testing period. Also, we indicate if any holes became 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 — it's designed to be used with another thicker, more durable overlayer. These tests just allowed us to see which fabrics were more fragile than others. Lastly, we noted which layers were odor free and which layers became smelly after minimal use.

long underwear womens - after use (both alone and with a layered system) we evaluate the...
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.
Credit: Edward Kemper

Ad-free. Influence-free. Powered by Testing.

GearLab is founded on the principle of honest, objective, reviews. Our experts test thousands of products each year using thoughtful test plans that bring out key performance differences between competing products. And, to assure complete independence, we buy all the products we test ourselves. No cherry-picked units sent by manufacturers. No sponsored content. No ads. Just real, honest, side-by-side testing and comparison.

Learn More