I strongly recommend Columbia’s Midweight Stretch Long Sleeve Tops because I have worn them from frigid South American mountain ranges to chilly New York suburbs and they always help with ideal temperature regulation. 

First things first, let’s get a bit of clarity here: yes, the garment we’re discussing here is technically a base layer, meaning it is worn underneath your puffer, shell, parka, or whatever other layers of technical apparel the conditions you’re facing may merit. But no, to be honest, I almost never wear my “base layer” shirts from Columbia that way. 

Why? Well, no fault of the shirt, to be sure.

They’re so warm on their own that layering up is often unnecessary for the neighborhood jogs or local hikes I do even in the depths of an east coast Mid-Atlantic winter.

Before writing this review, I went for a run wearing one of my Columbia base layer shirts, a pair of shorts, and socks and shoes. (And I’m being 100% honest here, I really did this about 45 minutes ago.) The temperature out, according to my weather app, was 52 degrees Fahrenheit when I stepped out of the house. And when I stepped out, that felt pretty cold, especially on my exposed legs.

Within a few minutes of jogging, however, I was starting to warm up. And within maybe five minutes at most, I was warm. Partially, of course, this was due to my own body’s internal mechanics as I burned calories and endothermic processes created heat. But it was also thanks to two aspects integral to my base layer. 

First, the polyester/elastane blend of fabric itself blocks some of the wind and chill and keeps in some of the heat a human body produces. But second is the Omni-Heat lining on the inside of the shirt.

You know those metallic-looking blankets marathon runners don after racing or accident victims are covered with after, well, accidents? Those space blanket things, right. They may be paper thin, but man are they effective at trapping in heat. (Or blocking it out, both of which are reasons NASA uses similar materials, thus the whole “space” in the blanket of it all.)

Omni-Heat is a proprietary technology developed by Columbia’s scientists (and yes, they are actual scientists – I have had dinner with one of them) that makes use of the thermal reflective properties of these thin metallic layers, but that employs them in a brilliant way.

Rather than a solid sheet of metallic material, which would trap in way too much heat and moisture, making you sweat bullets then freeze (potentially literally), the insulation is applied to the interior of the fabric in a matrix of dots.

The result is that about half of the shirt is reflecting your own body heat right back to you, while the other half is letting you release moisture (AKA sweat) and excess heat so you don’t overheat. That’s a comfort for neighborhood jogs, and a potential lifesaver when you’re far afield (say… Antarctic jaunt?) when sweat can turn to ice against your skin faster than you’d believe.

In terms of fit and feel, the Midweight Stretch Shirt is flexible and comfortable, in no way restricting motion. And I say that having worn one doing everything from running to rock climbing to kayaking to just kicking back and taking it easy in the evening.

And yes, these shirts are also a great choice for anyone who runs cold and wants to take their pajama game up a notch. Which could not apply to me less – I was kicking back fireside on an evening in the 45-dregree range – but may be good news for you if you find yourself chilly when hitting the couch at night.