Enough for You?
Heat Related Illness and
Heat Injuries in Mountain Bikers
By Brian Fukushima, MD
NMBP Medical Advisor
You are riding on a difficult, exposed trail with a significant
elevation gain. It is the middle of the afternoon on a muggy
summer day. You come across two riders panting by the side of the
trail. One of the riders complains of nausea, dizziness, and
fatigue. On examination, he is breathing rapidly but without
difficulty, his heart rate is rapid, and his skin feels very warm.
He says he feels ok, but just needed to stop for a short rest.
What is your diagnois and what do you do next?
Heat related illnesses can be common injuries especially among
athletes engaged in strenuous activities of long duration. Heat
injuries are usually the result of a combination of factors
Increased environmental temperature and humidity: Ever try
riding Utah's White Rim Trail in the middle of summer, or
hiking the Kalalau Trail on Kauai during the middle of the
day? Direct exposure to sunlight, heat, or humidity can
increase the body's temperature.
Increased heat production: Intense physical activity can
increase the body's production of heat. Strenuous exercise can
increase the body's temperature 1 degree every 5 minutes (if
heat production cannot be dissipated).
Decreased heat dispersion: The body may lose its ability to
effectively get rid of excess heat. This is usually the result
of dehydration. Another important factor is clothing choice.
Most high-quality cycling apparel is designed to maximize
wicking and aid in heat dispersion, but novice riders will
often choose heavier cotton or other non-wicking materials
that impede the body's efforts to shed heat.
A sampling of heat injuries
There are two main types of heat injuries, ranging from mild heat
exhaustion to life-threatening heat stroke.
This common condition is usually the result of salt and water
(volume) depletion. The body's temperature is usually within a
range from normal (98 degrees) to 104 degrees Farenheit.
When you examine a rider suffering from heat exhaustion you may
rapid heart rate
increased body temperature
fainting or lighheadedness when standing from decreased blood
Rest. Remove the cyclist from direct heat or sun exposure
into shade or shelter.
Remove excessive clothing.
Use cool compresses or ice directly on the skin.
Provide fluid to the injured cyclist. Water is acceptable
but sports drinks contain fluid plus electrolytes.
Additionally, since sports drinks are flavored or sweetened
the cyclist may be willing to drink more.
As outdoor athletes, many of us have suffered from the symptoms
of heat exhaustion. These symptoms usually respond to rest,
cooling, and hydration. While not severe, if untreated the
symptoms can escalate into a serious condition known as heat
Heat stroke occurs when the body is no longer able to
effectively cool itself and begins to shut down. It should be
treated as a medial emergency with immediate evacuation and
treatment in a hospital setting.
A patient with heat stroke will have a temperature above 105
degrees Farenheit, nervous system degradation, and a lack of
Symptoms may include:
All the signs and symptoms of heat exhaustion
These symptoms demonstrate involvement of the central nervous
system (brain and spinal cord). Many of us ride with friends
with these symptoms (usually brought on by a certain beverage)
but in the setting of heat and sun exposure, suspect heat
Other signs of heat stroke may include:
Excessive body temperature
Dry skin and lack of ability to sweat
Abnormal body posturing
Cool down the body temperature!
The immediate (field) treatment for heat stoke is rapid cooling
to below 104 degrees Farenheit. Ice packs placed in the armpit
and groin and cool, moist compresses will help decrease the
cyclist's temperature. Fanning the patient or encouraging the
flow of air over the cyclist's body will also help decrease the
patient's temperature. Also remember the ABC's of first aid
(airway, breathing, circulation) especially when dealing with a
patient with nervous system problems. Finally, evacuation to the
hospital for more specialized treatment is essential.
Heat stroke is much more severe than heat exhaustion. It is a
life-threatening emergency. Heat exhaustion is far more common
on the trail and can vary in severity from a minor distraction
to debilitating weakness. Usually heat illnesses can be
prevented with proper hydration, clothing, preparedness and
knowledge of conditions.
For further information, contact:
Emergicare Medical Training