How To Identify The Warning Signs of Heat-Illness While Training In Summer Weather

Guest Blogger: Aaron Vaughan, M.D.
MAHEC Family Medicine Physician, Sports Medicine Director
MAHEC Primary Care Sports Medicine Fellowship Director

Our steamy summer months are upon us and it is important for athletes to understand how the environment affects exercise and to identify the warning signs of heat-illness.

Environmental heat stressors include both the air temperature as well as relative humidity. The combination of these two elements is termed the “heat index,” or the “apparent temperature” that our bodies experience. When exercising in humid conditions the body tends to sweat less leading to an inability to cool efficiently and ultimately leading to decreased exercise tolerance and poor performance.


Training In The HeatThe “Wet Bulb Globe Temperature” is an index that takes into account the heat (dry bulb), humidity (wet bulb), and the ambient temperature (black bulb which factors in additional variables such as reflected heat and wind). The American College of Sports Medicine has issued the following guidelines for exercise and sports in the following conditions:

  • WBGT >82° F (>28° C) Black Flag: Cancel or recommend voluntary withdrawal. (Races that are always held in these conditions should acknowledge the extreme heat risk to the poorly acclimated and non-resident competitors in the pre-race literature and the pre-race announcements).
  • WBGT 73° F – 82° F (23° C – 28° C) Red Flag: Recommend participants at increased risk for heat collapse withdraw from race and others slow pace to match conditions.
  • WBGT 65° F – 72° F (18° C – 22° C) Yellow Flag: Recommend participants at increased risk for heat collapse slow pace. Warn entrants of increased risk of heat collapse.
  • WBGT <65° F (<18° C) Green Flag: Collapse can still occur. Decreased risk of hyperthermic and hypothermic collapse.
  • WBGT <50° F (<10° C) White Flag: Increased risk of hypothermic collapse.

WBGT is most easily calculated through various online calculators (e.g. and can be utilized to modify exercise, optimize performance, and promote safety.


If exercise or activity overwhelms our body’s cooling mechanisms, heat illness can occur. Heat-related illness can be considered a spectrum condition that can start with mild symptoms but can lead to serious long-term complications and even death if left untreated.


  • Heat cramps: Painful muscle contractions and spasms that occur with


  • Feelings of lightheadedness or fainting. This more commonly occurs immediately after stopping exercise.
  • Heat exhaustion: Suspected in an athlete whose performance rapidly declines and inhibits the ability to continue exercising. Athletes may experience extreme thirst, dizziness, headache, profuse sweating, weak and rapid pulse, as well as gray, cool, clammy skin. Body temperature can rise as high as 104°F.


  • Heat stroke: Body temperatures rise to above 104°F with symptoms of confusion, disorientation, profuse sweating, hot, red skin, hyperventilation, loss of balance and possible loss of consciousness.


If you develop any of these symptoms, it is important to modify your activity and
lower your body temperature.

Mild symptoms:

  • Fluid intake, rest in a cool area, massage and stretching of cramping muscles, and elevate swollen limbs.


  • Seek immediate medical attention.
  • Whole body immersion in cold water.
  • This the fastest and most efficient way to rapidly cool the body
  • Beware of rebound hyperthermia (rise in body temperatures following removal from cold immersion).
  • Do not administer fever-reducing medication.

If you suffer from a heat-related illness, you should be seen by a physician prior to returning to exercise. Plan for a gradual return to your full level of activity taking into account intensity, duration, and heat exposure.


To prevent heat related illness, it is important to consider the following:

  • Acclimate: Exercise and train in environments similar to those expected on competition days; ~ 10-14 days.
  • Apparel: Clothing should be lightly colored, lightweight, moisture wicking, and protective against the sun.
  • Hydration: Sports drinks and electrolyte tablets can be beneficial for endurance athletes. Drink plenty of fluids and electrolytes before, during, and after exercise. Caution items that are carbonated or contain caffeine.
  • Appropriate activity modification: Exercise and compete based on heat, humidity, and prior history of injury and toleration as well as level of training.

About Glory Hound Events

Glory Hound Events was started in 2006, initially managing the historic Bele Chere 5K. Shortly after that first year the Lake Logan Triathlon was introduced and eventually became a part of the Lake Logan Multisport Festival. Glory Hound Events is now the largest endurance event management company in the Western North Carolina region, producing an average of twelve events annually. In addition to producing its own events and those for a variety of clients, Glory Hound Events offers consulting services for events outside of Western North Carolina looking to take theirs to the next level.