Doc’s Talk 04-22-2012

Dr. Scaff talked about how to prevent overheating.

As Dr. Scaff has previously noted (04/01/12), you can think of your body like an internal combustion engine:  It has cylinders (legs), a carburetor that distributes the oxygen (lungs), it has a fuel system (heart and vessels), it burns fossil fuel (i.e. you eat animal fats and vegetative matter), it generates heat, and has a radiator (your chest).

If we don’t dissipate enough heat, we overheat and collapse.

Heat is a byproduct of work, and as you begin to exercise, your body temperature rises.  As body temperature rises, your body produces sweat in order to dissipate heat (the process of becoming cooler).

As mankind evolved, the human body developed features that enable us to run long distances, including unique factors that help us dissipate body heat.  For instance, man became hairless, a real radiation advantage, while retaining enough hair on our chest and other areas to wick sweat which is cooled by air circulation and further dissipates heat.  We also dissipate heat through our chest, in fact, the human chest is incapable of conserving heat (hence the creation of the Farmer John style wet suit for swimming, snorkeling, diving, and surfing).

There are 4 ways to exchange heat:

  1. Radiation:  Like the heat emitted by a light bulb.
  2. Convection:  Heat rises.  You can see convection at work when you see steam rising off of athletes playing winter sports.
  3. Conduction:  The direct transfer of heat.  When you sit on a cold bench, you are conducting heat from your body.
  4. Evaporation:  While running, air flows over your body promoting evaporation.

As you may recall from science class, it takes 1 calorie (a calorie is a measure of heat exchange) to raise 1 gram of water by 1 degree Centigrade (Celsius).

It takes 300 calories to evaporate 1 gram of water.

Evaporation is 500 times as effective as all other forms of heat exchange combined.

Thus, evaporation is the most effective way to cool down through heat exchange.

From this you can understand that every drop of sweat that hits the ground, instead of being held around your body where it can dissipate heat, is a drop of cooling bodily fluid that is wasted.

Running singlets help keep you cooler than if you run without a shirt on because as the singlet wicks and holds the moisture from the body, air is allowed to circulate through the holes in the material, promoting evaporation, which keeps you cooler.

Light colored clothing is better for keeping cool than dark colored clothing, which holds more heat.  Cotton shirts are not as good at exchanging heat as tech shirts (technical running shirts).  Feel a runner’s singlet as contrasted to a cotton t-shirt.  You will find that the cotton shirt is warm, while the singlet is cooler because it has the double advantage of trapping perspiration while allowing circulation.

Another important factor in preventing overheating is to drink enough liquid.
Forget the recommendations that say you have to drink 8 glasses of water per day.  You need to drink the amount that is sufficient for you.   How do you determine that?  You should drink an amount of fluids that enable you to:

1) Urinate within 4 hours of your run, and
2) Have colorless urine once per day.

Drinking water and eating pretzels will do a fine job of replenishing your electrolytes.


Dr. Scaff announced that his book will be featured at the 7th Annual Hawai‘i Book & Music Festival at the Civic Grounds at Honolulu Hale
in Downtown Honolulu, May 5 – 6, 2012,
10 a.m. – 5 p.m.  Everyone is welcome to attend this event.  For more information see:

If you are interested in acquiring a copy of the book, Your First Marathon – The Last Word In Long Distance Running, by Jack H. Scaff Jr., M.D., F.A.C.S.M., available for purchase at the Honolulu Marathon Clinic on Sundays and online at:


For some good reading on nutrition, Dr. Scaff recommends everyone check out the daily postings on Dr. Alan Titchenal’s “Got Nutrients?” web site:

Here is a recent posting:

April 16, 2012
More is not always better when it comes to athletic training. The best training programs balance the stress of exercise with adequate rest time for recovery from the workout stress. The body cannot adapt and strengthen without proper recovery.

Consumer Link
Nearly 30 Percent of All College Athlete Injuries a Result of ‘Overuse’

Research Link
Journal of Athletic Training, Vol. 47, Number 2, March/April 2012 , pp. 198-204(7)