Beat the Heat!

Recognition, prevention, and treatment of exertion heat illness


It’s that time of year again…. it’s 98 degrees in North Carolina today.  The “low” was 75, so there’s no such thing as a “cool morning run”, and my dog is now refusing to walk for longer than ten minutes.

See where I’m going with this? If you’re training outdoors this summer, you’re at risk for exertional heat illness.  Even the dog knows it J. Most people refer to heat illness as “heat stroke”, but there are actually three types of heat illness, each a different severity.

Heat Exhaustion:is simply defined as an inability to exercise effectively in the heat.  High temperatures, and the body’s subsequent increase in heat dissipation needs, leads to increased heart rate and decreased blood pressure as the heart works overtime trying to pump enough blood to the body’s surface for heat dissipation. This leads to feelings of fatigue and an inability to perform, as well as heavy sweating and dehydration.  While heat exhaustion is not a medical emergency it can quickly progress, so it’s best to stop exercise if experiencing these symptoms.Symptoms:Muscle fatigue, cognitive fatigue, collapse, cognitive changes, dizziness, weakness, vomiting

Heat Syncope:“Syncope” is essentially the fancy medical term for “passing out”.  This is also due to the body’s increased need for heat dissipation, which results in an increased heart rate and decreased blood pressure – poor cardiac performance or cardiac insufficiency.  This leads to dizziness and can even lead to momentary loss of consciousness. It most often occurs in unfit people and is usually due to standing in the heat for long periods of time, as opposed to exercise. Symptoms:  dizziness, fainting, tunnel vision, pale skin

Heat Stroke:The most severe type of heat illness, which usually results from body temperatures over 40.5 degrees Celsius/105 degrees farenheight.  Heat stroke is characterized by central nervous system dysfunction – people experiencing heat stroke may present with confusion, altered speech, or altered levels of consciousness. Heat stroke is always a medical emergency. Symptoms: Core body temperature over 105 degrees Fahrenheit, cognitive changes, confusion, dizziness, unusual behavior, loss of balance, difficulty walking

Who’s at risk? In general, everyone exercising outside in the summer.  Specifically, in temps over 82 degrees Fahrenheit. Children, older adults, and obese persons are at greater risk of heat illness compared to others, as they have difficulty dissipating body heat.

So…how do you prevent heat illness? Right off the bat – if you can move your workout to dawn or dusk, you’’ll cut your risk by a lot.  I don’t enjoy waking up early on Saturdays (I swear I’m a normal person deep down…), but it’s worth it to get my run in and not have to be on the dreadmill. If you MUST exercise during the heat of the day, take it indoors.

Is exercise in the heat unavoidable?  Then you can start by making sure you’re appropriately ACCLIMATED to the heat.  Generally, this takes about two weeks of gradually increasing duration and intensity of exercise until you reach your typical workload, or slightly less. Runners, expect to feel slow and out of shape for the first few weeks of summer running. It’s okay – you’re not out of shape, you’re just not acclimated yet.  As bad as it feels to be slow, resist the temptation to push the pace here – you’re putting yourself at risk.

Every state has slightly different rules – check yours for the temperatures and humidity levels at which games and practices must be called off.  In North Carolina, it’s 92.1 degrees F. This is a good general guideline for when to call off your run or take it indoors.  If you’re cycling, you can generally push the temperature a bit as you’re moving fast above ground – more of a breeze (same reason that temps which are too cold for cycling are just fine for running).

If you’re training in the heat, even when you’re acclimated, pay attention to your heart rate, find as much shade as you possibly can, take frequent rest breaks during longer workouts (60min and over), and make sure you are always in reach of hydration – not just water, but also electrolytes.

But what if it’s too late? What if you notice your running buddy or your teammate starting to show some of the signs and symptoms of heat illness listed above?


-Stop exercising (that should be obvious…)

-Find some shade, or find a place with air conditioning

-Take their temperature if you can.  The gold standard is rectal temperature (yes…that means what you think it means), so if you happen to have a thermometer on you, stick it where it counts. No thermometer?  Call EMS.

-If the person’s condition is worsening and/or you can’t find shade and/or can’t access water or a way of cooling them, and/or if you don’t have access to a thermometer, I would STRONGLY consider calling EMS.

-For heat stroke, a person will often need to be immersed in an ice bath for core temperature cooling. No access to an ice bath? Call EMS.

-…. when in doubt, call EMS.

Once the immediate illness is resolved, what next?  First, and I think this should go without saying, but there are some die-hards out there so I probably need to say it – your run/race/workout is done for the day. Go home.  Don’t try again for AT LEAST another 24 hours.  This is one of those rare instances in which I will tell a person to refrain from exercising at all. Depending on the severity of the heat illness, you may need to take up to 2-4 weeks off from sport, after which you will need to RE-ACCLIMATE to the heat while progressively working back up to your prior level of training.

Summers are only going to get hotter in the US – I hope the information in this article empowers you to continue your training while minimizing your risk of heat illness.

Happy Running!

One Comment Add yours

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s