Loose, airy shirts can be a dream in hot, dry weather, they flap and promote air circulation. A sheer, close-to-the-skin shirt can wick moisture away from your skin better, helping to regulate temperature differently. However, with a skin-tight shirt, you’ll have more contact points and friction, which can increase your risk of punctures (ouch).
For some, the fit of the shirt is too good; some people find a cropped or loose shirt more flattering. Although there are slight functional differences, comfort should be your top priority when it comes to fitting – whether that means how the fabric feels against your skin or whether you feel comfortable with the style of the shirt.
When choosing a shirt, you may see “slim fit,” “regular fit,” or occasionally, you’ll unfortunately see the word “athletic fit.” When this term is used, it may refer to a larger cut at the shoulders, with more cuts coming down from the waist. This fit is the opposite of a straight, symmetrical cut from the shoulders to the waist, such as a regular or slim fit. We cannot understand how the word ‘athletic’ refers to fitness more than physical form. It’s an imprecise term in terms of what constitutes an athletic look because athleticism comes in all shapes and sizes.
Our reviewer’s choice is a running shirt that’s baggy and long enough to fit comfortably in his running belt or a pair of low-waisted shorts over an undergarment. One might describe this as “track performance parity” in the world of road and track or old-school track looks.
Range of motion
You don’t want a shirt that restricts the natural motion of your run. For more slim fit shirts, to get a good range of motion, brands may incorporate stretchy fabrics like spandex and even add more nylon, which is usually more stretchy than polyester and holds its shape better when not stretched. The range of motion is accurate, so if it doesn’t feel right when you try it on, get another shirt. We recommend going with a broker with Easy returns like REI or free shipping on returns like Zappos.
Flatlock seams
Flatlock seams—or low-profile, chafe-friendly seams—are found in most polyester and nylon running shirts, and to a lesser extent, in merino wool running shirts.
If you look at the construction of the inner sides of one of your normal everyday cotton shirts, it probably has an unlocked seam. You will see a flap where two pieces of fabric are layered on top of each other; when sewn, this results in a flap, or seam allowance, of approximately 1cm.
In contrast, the flatlock stitch avoids that opening by joining two pieces of fabric without overlapping. The flatlock stitch is more complicated to sew and is made with different machines, but it is very comfortable for jogging or active wear.
With merino wool, if the shirt does not have a flatlock seam, there is probably no need to worry. Merino wool is generally softer than nylon and polyester and doesn’t cause as many puncture problems. Also, it is unlikely that a merino shirt or any full merino wool garment will fit because it is not the lightest material and usually does not hold its shape well when stretched.
Flatlock seams are especially useful if you’re wearing a running hydration pack or running belt, which can bounce or rub to create more friction.