Running shorts are a specialized form of shorts worn by runners.
Running shorts are designed to facilitate comfort and free movement during exercise. Their materials are lightweight and hard-wearing. Many running shorts include an inner lining that acts as underwear, so you don't have to wear underwear with running shorts. Polyester is a common fabric in running shorts.
Many running shorts have a seam cut up the side of each leg to enable freer movement. Manufacturers define running shorts according to the length of the leg which is not cut. For example, a 3/4 seam means that 1/4 of the length is cut.
Longer shorts are not ideal for running. A runner's stride may pull up the fabric of his or her shorts, which can cause discomfort. Nonetheless, some runners prefer longer shorts because they cover a greater portion of their legs.
Some runners use athletic hot pants as running shorts. Like 1/2 split seam shorts, hot pants do not encumber leg movement.
Lycra running shorts are an alternative to conventional, polyester-based shorts. In most cases, lycra running shorts reach the mid-thigh area. They are skin-tight, so they allow for more flexible, unencumbered movement.