Mens gym shorts may mean different things to different people. Depending on the style and use, the can be long or short, baggy or tight fitting. The definition can mean different things to different people. There does not seem to be a consensus on what these items actually are other than they are for men and they end somewhere above the knee.
To some, gym shorts mean those unflattering short pants that kids wore during PE in school. Usually they did not fit very well because they were generic and supposed to be all things to all people. The male version of these many times looked odd because they seemed to short. They were not something people kept after their school years and treasured.
Other versions of these resemble baggy boxer shorts. These come in longer versions with some having 11 inseams. These look pretty comfortable and close to what professional basketball players wear as to style and length. The come in a variety of fabrics ranging from polyester to mesh fleece. Some have elasticized waistbands with interior drawstrings. Men like to wear these for casual wear or on weekends with a favorite tee shirt. Some may have a sports team theme but most are more generic.
Some gym shorts for men are very short in length and favored by runners and others who get very hot when they work out. These may have as short as a 5 inseam and have a somewhat loose fit. Many of these have a small slit on the side seam as a design detail. Others who work out like the fleece fabric offerings that are longer in length. Some of these fit fairly close to the leg while others are a little more baggy. Some of these have zippered pockets. This detail is useful for wearing to the gym or the active man who is out and about.
Sometimes the general shape of gym or workout shorts comes from a particular sport. In addition to the looser basketball style, some shapes are reminiscent of actual boxer or martial art style clothing and more form fitting.
The detailing on this type of clothing varies from manufacturer to manufacturer. These items are available in many different fabrics but most are blends of some kind. One recent offering was 92% polyester and 8% spandex. This makes the pants more stretchable than some but also allows the bright colors to stay bright through many washings. Some have drawstrings that allow the waist to be adjusted. Sometimes the drawstrings have a mechanism that holds them in place so they do not move around and chafe skin. Pockets and their placement varies with some in front and others in back and sometimes having zippers or flaps. Mens gym shorts can also have top stitching, logos or other design details.