When you exercise, sweat evaporates off your skin, cools your body off, and regulates your body temperature. So it is important to dress appropriately. In summer you need to keep the body cool. In winter you need to dress warm enough, but also realize that your body will warm up as you run.
Cotton apparel: is absorbent, wicks moisture, but holds onto it. Dries very slowly. Gets heavy when wet. And is a rough fiber.
Coolmax (or other fibers like it): wick moisture away from skin to let it dry. And is a smoother fiber.
Running accessories are also available in coolmax: gloves, hats, headbands, socks. It is important to wear coolmax socks, especially on the long runs, to avoid blisters. Cotton socks hold on to moisture, rub and can cause blisters.
Chafing occurs when skin rubs against skin on a long run, or fabric against skin. This can occur on runs of 7 miles or so, and longer. Coolmax is a better fabric to wear as it is a smoother fiber and will minimize chafing. You can use Vaseline or even better, Body glide, on your next run on those areas to prevent further chafing. Men have a problem with chafing on nipples. They can try Vaseline, body glide or best of all nipguards (bandaids).
Rules of thumb to work with:
Above 45degrees: shorts and short sleeve shirt
Below 45: tights and long sleeve
In the winter, you should be chilly before you start running. If you are comfortable standing around in the parking lot, you are wearing too much. There is also the 20 degree rule: dress like it is 20 degrees warmer than it actually is to take into account how much your body is going to warm up.
When trying to gauge what to wear, think about how long you are going to be out. If it is 48 degrees at the start of the run, 2 hours later it could be in the upper 50s. On the other hand, if it is cold, don’t under dress. You will unconsciously run too fast.
You do want coolmax apparel to be fitted. When it is against your skin it does best at wicking the moisture away from you.
After you finish the run you will get cold as your body cools back down. Bring a change of clothes so that after the long run you can change into something dry.
Race Day: never wear anything new that you haven’t tried out on a long run before. For those in the group who are going to “race” it, wear less than you would on a slow long run. You will warm up since you are running a faster pace.