Heat Considerations for the Runner

There are a number of environmental considerations that will affect the effort and performance of the cross-country runner.  One of the physiological results of running at any speed is an increase in internal heat production which is due to an increase in the metabolism of the athlete.  If the environmental conditions are kind, the athlete is able to effectively rid themselves of this excess heat.  If however the environment is excessively hot, humid, or both, than the body struggles to dissipate this increased metabolic heat.  The main means for dissipating excess heat is through the linked chain of conduction-convection-evaporation in the human body.  Ideally, heat that is built up internally moves from the body’s core to the surface, heat is then transferred to the environment through convection and the evaporation of sweat.  Trouble could occur in any of the three links, but is most likely to occur when heat does not leave the surface.  This will ultimately cause a back-up in the chain and could result in heat stress to the athlete as core temperature continues to rise.

The goal of the athlete and coach is to create a situation where despite the environmental conditions, metabolic heat continues to transfer to the environment.  This goal can be addressed in many ways, and if conditions are severe enough it will have to be addressed in all of the ways.  The important points to consider:

• Keeping the body core cool needs to be addressed.  The best means for achieving this is to slow the pace down: in other words lower the metabolism.  Do not go for a fast run on a very hot day.
• Make sure conduction is at maximum.  The best means for achieving this is to make sure the blood volume is at maximum levels.  Keep the hydration high.  Go on long runs on very hot days only when you have the aerobic adaptations to do that.
• Maximize the body’s convection possibilities.  Wear loose fitting clothes on hot and humid days, or no shirt at all.  Wear modern quick-drying fabrics, and do not wear cotton.  Shade the face with a modern fabric cap.
• Keep evaporation occurring on the body’s surface areas.  The human body is nearly 70% water, and even a small water loss has drastic effects and will cause blood and sweat volume level problems as a first response.  In addition, the most effective sweat has an electrolyte composition to it that must be maintained during heat stress.

As heat stress occurs during exercise it could pass through several stages.  The early stages are mainly discomfort with later stages being very dangerous.  Physiologists have categorized the three stages as:

• Heat cramps: sodium and potassium loss and dehydration.  Treat by hydrating with water and feeding with electrolyte drinks.
• Heat exhaustion: body core temperature hovering near 103 degrees.  The treatment is stopping the activity, moving to the shade, elevating the feet and hydrating.  Seek medical aid.
• Heat stroke: core temperature at 105 degrees and climbing.  The treatment is the same as heat exhaustion, with the addition of packing in ice. Seek medical help immediately.

The coach needs to schedule the running workouts at a time of day that will be most effective.  In addition, if the athlete travels to compete in hotter weather, the coach needs to develop workouts to allow the athlete to acclimatize.  Below is a list of coaching cues for you to discuss with your team prior to summer running or the start of the fall cross country season.

• Make a note to discuss with your team the importance of hydration and the need for electrolytes before and after practice on all days, but especially the days with a higher heat index.
• Keep a list of treatments in your running or coaching log in case you have to react quickly to heat stress in your runners.
• Study the concept of acclimation.  Understand the time periods involved as your runners try to travel and compete in more tropical weather conditions than they are used to.