Why shouldn't you wear tight fitting clothing while exercising?

It can be very uncomfortable to wear tight fitting clothing if it limits your range of motion during exercise. Also, many types of tight fitting clothing do not have very good ventilation, meaning that you could become very hot and sweaty during moderate exercise. Of course, this applies only to some types of clothing. A number of tight-fitting clothing styles such as Under-Armor stretch to allow for movement and do vent very well, making it a reasonable choice for exercise.