The clothing that you wear while running depends on the season and the climate in the area where you live. If the weather is very cold, you should wear either sweatpants or cotton pants in order to keep your legs warm. Also, you should wear a t-shirt with a sweatshirt over it. This way, if you get hot after running for a while, you can just take off your sweatshirt and tie it around your waist. If the weather is mild, wear a t-shirt and a pair of lightweight pants, such as nylon jogging pants. Consider bringing a long-sleeved t-shirt along if the weather is brisk. If the weather is hot, you should wear lightweight cotton-nylon blend shorts with a comfortable tank top of t-shirt.
avoid cotton.