Men's Running Shorts (Activewear)

A running short is defined by its hem, not its length. The outer side seam is either split open for the last two inches or notched into a curve, so the fabric never catches the top of your thigh as the leg swings forward. Inseams sit between 3 and 7 inches. A liner, meaning a brief or a short boxer sewn permanently inside, comes as part of the short rather than as an option.

Weight explains the rest. Shells use thin woven nylon or polyester at the light end of what a mill can make, because wet fabric weighs more and holds heat against you. Seams are flatlocked, meaning stitched so the join lies level instead of forming a ridge, since a ridge at the inner thigh turns into a raw patch over ten miles. Waistbands run wide and soft with an internal drawcord, spreading pressure across your stomach while you breathe hard.

Against training shorts, the difference is purpose. Those run 7 to 9 inches in a heavier stretch knit with no liner, built for squats and lateral work. They hold sweat once you push past a few miles. Athletic shorts sit between the two and lean casual. Joggers cover the whole leg for warm-ups rather than the run itself. Deep zip pockets and a knit hand are the giveaway that a short was made for the gym floor, not the road.

Runners logging real distance in warm weather get the most from these. Racing suits the 3 to 5 inch range, where the leg is completely free. Bare thigh puts some people off, and the fix is a 2-in-1, which layers a compression short under the shell and adds a couple of ounces. Lifters should shop elsewhere, because the fabric is too thin to sit on a bench and the pockets hold nothing bigger than a key.

Judge the liner first, since it decides whether you finish comfortable. Pull it inside out and feel for a soft bound edge rather than exposed elastic at the leg. Test the waistband by tugging the cord: it should gather evenly instead of bunching at the front. Wash cold, hang dry, and skip softener, which coats the fibers and stops them shedding sweat.