Training in Heat & Humidity

As training continues into late summer and school sport two-a-days begin, there is one element that we must not overlook: the heat. Sword Performance Co-Founder and Sports Medicine physician, Dr. Black lends some insight on how temperature affects our bodies, our training, and how we can stay safe while getting the most out of our summer.


What makes training in extreme heat & humidity dangerous?

Anytime we do physical work (bike, run, play sports, labor jobs) our muscles produce a lot of heat.  That heat raises our body temperature.  In order for the body to lose heat, we need a temperature gradient between our body and the environment.  The larger the temperature difference, the easier it is for our body to lose heat (think about jumping in cold water).  On a really hot day, we don't have a temperature gradient with the environment so we have a harder time losing the heat our muscles are producing.  In addition, the most IMPORTANT way we lose heat is through sweating.  However, people need to understand that for sweating to reduce our body temperature, THE SWEAT MUST EVAPORATE.  In humid conditions, the sweat doesn't evaporate so we lose our most important cooling mechanism.  People can overheat in moderate temperatures that have high humidity.

What are the risks of heat stroke, and what are the signs I should look for?

Heat stroke is a very dangerous condition that is often fatal if not recognized and managed promptly.  Two things make the diagnosis:  1) Elevated body temperature (almost always above 104); and 2) Altered central nervous system function...confusion, delirium, loss of consciousness, seizures, etc.  Anytime someone at risk of heat stroke seems confused, that is a medical emergency.  The only effective treatment is rapid whole body active cooling.  Simply putting someone in the shade will not fix the problem.  You have to set-up a big temperature gradient and get the body to dump the excess heat.  Whole body immersion in cold water is the preferred treatment.  Hydration will not fix heat stroke.

How should I stay hydrated in extreme heat & humidity?

Maintaining hydration helps the body maintain fluid volume which can help with cooling, but the main preventative for heat stroke is reducing the intensity of physical activity.  The harder we work, the more heat we produce.  So, we have to SLOW DOWN in the heat.  That being said, trying to stay properly hydrated is important.  Sweat rates vary by person, exercise intensity, and environmental conditions, so it is difficult to make a one-recommendation-fits-all statement.  The best process is to have plenty of SWORD and water available.  Keep it COLD.  Give players free access to it so they can drink whenever they want and take scheduled rest breaks for them to cool off and encourage them to drink at that time.  Have the players listen to their thirst.  If they're thirsty...drink.

What is over-hydrating?

Over-hydrating can occur in one of two settings: 1) Someone is either forced or forces them self to consume too much fluid...drinking way beyond thirst; or 2) In some longer-distance events, the stress of the event can produce a syndrome called inappropriate anti-diuretic hormone secretion.  If that occurs, the body retains too much fluid and does not regulate its plasma osmolality and sodium concentration appropriately.  In this case, the person is again drinking beyond body needs, and likely way beyond thirst.

Are there myths about heat stroke or training in extreme heat?

Yes. The most common myth is that a person with heat stroke is not sweating or has cool skin. That is completely wrong. A person with heat stroke has mental status changes (CNS changes) in an environment in which heat stroke is likely. That person could be hot or cool to the touch with skin that could be wet or dry. The key is that their core body temperature is elevated and they have central nervous system abnormalities.

What else can I do to ensure my safety when training in the heat?

Humans are well-adapted to exercise in the heat and humidity and in fact we do it all the time.  An extreme example is an ultramarathon called Badwater 135 which runs straight through Death Valley in July. Now that is HOT. In general, the key for us this time of year is to SLOW DOWN. Maintaining proper hydration during the day and regularly consuming COLD liquids during exercise is very important. Lastly, we cannot underestimate early signs of heat exhaustion or heat stroke. If you sense someone might be having trouble handling the heat and humid environment, get help, immediately. Athletic trainers, coaching staff, and other qualified sports medicine professionals are trained to recognize the symptoms and act quickly. Unfortunately injuries related to heat and humidity in sport are far too common, and the combination of heavy exertion and high environmental heat stress (heat and humidity) is deadly.


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