Many years ago, runners and other athletes put on heavy cotton sweat suits when warming up or running outdoors. Then football players and runners discovered compression clothing, lightweight, tight-fitting garments which clung tightly to the body. While each garment has its advantages and disadvantages, especially in cold winter weather, they give runners options for both warmth and style.
Sweats Are Warm, Versatile
Sweat pants will keep your legs warm on a cold day, especially if they are the style with elastic around the ankles to seal in body heat. Sweat pants are also versatile, so one standard size may fit many runners. They come in different weights of cotton, so you can choose lightweight ones for mild days, heavier ones for colder days. They are long-lasting and easy to wash. Just toss them in the washer and dryer and don't worry.
The big disadvantages to sweat pants is that they don't block the wind and do retain moisture. Moisture retention can lead to chafing around the knees, ankles and other areas. The failure to block wind can be a serious problem on a long run when a lot of sweat builds up and the wind makes it cold. Sweat pants will even freeze in extremely bitter conditions.
Compression tights are just that -- pants which compress the body. That helps keep muscles warm and also helps prevent mild strains and pulls. Compression tights also avoid chafing problems, because the spandex fabric fits tightly against the skin and doesn't chafe as you run. Tights offer less wind resistance when moving, but the tighter weave of the material blocks wind from penetrating to the skin.
Tights Offer Options
Running tights come in a variety of options. Most fit tightly on the legs from hips to ankles, but knee-length and mid-calf capri styles also are common. Some have varied areas of compression to stress support for muscles most likely to be strained. All compression tight materials wick away moisture, so sweat or water buildup is not a problem. Some have special mesh openings behind the knees or in other areas prone to sweat.