Gatorade
Water Loss and Dehydration
Dr. Matt Hermes

Sports Science

Rehydration

Energy  Replacement

Quiz

Problems

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 0.3^o C when an individual participates in prolonged exercise in the heat."

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.

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