Water Loss and Dehydration
Dr. Matt Hermes

As a skilled basketball player like Sue Bird runs down the court in a crowded arena, she converts body mass -- carbohydrates, fats, and proteins -- to energy. Some of this energy is obvious. It appears on the court as work: graceful bounce passes, astonishing shots, and tenacious defense. This is the work of muscle and a finely tuned cardiovascular system.

The rest of the energy appears as heat. Sue's body produces heat in the muscles and cardiovascular system, but her body temperature must remain relatively stable. Perspiration evaporating from her skin provides the cooling she needs.

Sue Bird of the Seattle Storm in WNBA action

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We would find that Sue also loses some weight during the game.  As she runs the court, she converts the fuels to carbon dioxide and water and loses these oxidation products through exhalation.  She replenishes lost fluids by drinking throughout the game.

How does chemistry explain the fluid balance when we exercise?  Let us look at the processes taking place when we exert ourselves and how the limitations of those processes restrict our exertions. We might think of the exercising person as a system; a vessel in which chemical reactions take place. Let us consider a number of processes that occur:

  • We expel carbon dioxide produced in oxidation through respiration.
  • We eliminate urea through urination.
  • We lose water by urination, by perspiration, and as a component of expelled gases through respiration.
  • The sweat passing through the membrane of the skin contains salts from the body and deposits them on the surface of the skin.
  • Heat buildup is controlled by evaporation of water from the surface of the skin and by the expiration of water vapor through breathing.

Fact:  Fluid and salt loss and body heating retard physical performance. Prof. Coyle of the University of Texas writes, "Even a slight amount of dehydration causes physiological consequences. For example, every liter (2.2 lbs) of water lost will cause heart rate to be elevated by about eight beats per minute, cardiac output to decline by 1 L/min, and core temperature to rise by 0.3o C when an individual participates in prolonged exercise in the heat."

Like Sue Bird, the Florida football team that practiced on a humid summer afternoon in 1965 was also working hard. Their body chemistry converts the carbohydrates, fats, and proteins to energy, heat, water, carbon dioxide, and urea. Lots of energy. Lots of heat. Plenty of water. As they breathe, the water and carbon dioxide they exhale helps to cool them. With every breath the athlete depletes the water in the body. Their exhalations contain water vapor in equilibrium with their body temperature. They exhale not just the water produced with the energy, but the normal balance of fluid in our living system. This process is called dehydration.

Sweat drips from their skin. In the hot and humid environment, little of the perspiration evaporates so little cooling occurs. The athletes begin to heat up. This is called hyperthermia.

Within our cells, in the vascular system and in the extracellular spaces, are solutions containing salts. Water and small molecules like salts can pass through semipermeable membranes such as the skin. These membrane properties of the skin cause another difficulty for our football players. As they perspire, the water carries some salt away, but the water depletion far outstrips the transfer of salt through the skin. At its extreme, depletion of the body's water in the extracellular plasma causes radical changes. As the water concentration of the plasma drops, a difference in salt concentration between the extracellular fluid and the body's cells is established. By the process called osmosis, this difference in concentration causes water to flow from the cells into the fluid in an attempt to equalize the salt concentration between fluid and cells. The blood cells will shrink, the volume of blood decreases, blood pressure drops. In extreme cases, the combination of low blood pressure and low blood volume and can lead to catastrophic heat stroke.

In the years before Dr. Dana Shires brought the sports beverage he and Dr. Robert Cade had developed to Florida's football team, dehydration and hyperthermia were responsible for the deaths of dozens of athletes and military trainees. The development of Gatorade® depended upon an understanding of chemical reactions, thermochemistry, colligative properties and the acid-base properties.

We will see how Dr. Cade and his associate researchers used these simple chemical concepts to invent and develop Gatorade and we will use these principles ourselves to evaluate and decide on issues of testing and ownership of Gatorade

Chemical Concepts
Here are some concepts of solution chemistry that the inventors of Gatorade used in developing the sports drink:

5. Water Evaporation is Endothermic
cools its Source
6. Particles in Solution change solution Boiling Point
Freezing Point
Osmotic Pressure
7. Osmotic Pressure is a result of Force Moving Solvent through a Membrane from Less Concentrated to More Concentrated Solution
8. Isotonic Solutions are Solutions Containing the Same Concentration of Particles
Essential in Human Sysytems to Prevent Cell Crenation (Shriveling) or Hemolysis (Swelling)
Difficult to Maintain in the Exercising Athlete




©2003 Kennesaw State University
Principal Investigator Laurence Peterson
Project Director Matthew Hermes