Updated: Jun 19, 2020
With summer upon us, things are heating up on the trail! One of the safety concerns for hikers is heat stress. The body moves under loaded conditions. There are external loads, such as the weight of your pack and the incline of the climb. Then there are internal loads that are harder to quantify. The amount of internal load depends on many psychophysiological factors, such as the amount of sleep you’ve had, your mood, and underlying health conditions. Another issue that contributes to internal load is the environmental temperature. Heat stress can significantly increase your internal load, and lead to heat exhaustion and heatstroke.
How to recognize heat stress
I’ve grown up on the Gulf Coast, and we used to have all-day fourth of July events with parades and carnivals into the evening. As fun as it was, people would drop like flies from the heat and humidity. The medic tent saw almost as many people as the cakewalk booth. So in my family, if someone says it’s fourth of July hot, you know not to walk on the sidewalk in bare feet.
One of the problems with those all day fourth of July events was that there wasn’t a break from the heat. People suffered from the cumulative effects of the heat as the day went on if they stayed out all day. In a humid climate like the Gulf Coast, sweating isn’t an effective means of cooling the body. Under ideal conditions, sweat evaporates, and it’s the evaporative action that cools you off. Evaporation is an endothermic reaction. As the liquid sweat changes to a gas, it absorbs heat from your body and makes you feel cooler. Sweat isn’t able to evaporate in air that contains more than 60% relative humidity. Therefore, in this environment the sweat drips off rather than evaporates, leaving you hot and wet.
Forests can be humid environments, and while cooler because of the shade, the added humidity means your body won’t dissipate heat as rapidly. Though not humid, desert and arid climates can be quite hot. Thus, spending all day in the heat of a desert hike means your sweat mechanism works well. However, you may sweat more profusely than you realize because it evaporates so quickly, you may never feel sweaty. Thus it’s easy to become dehydrated and stop sweating in this environment. Without your natural cooling mechanism, the cumulative effects of heat stress can become dangerous.
Heat stress can lead to heat exhaustion. The signs of heat exhaustion include:
· Cool, clammy skin or shivering in the heat
· Profuse sweating or lack of sweating
· Feeling dizzy, faint, or confused
· Fatigue or extreme lack of energy
· A weak, rapid pulse
· Muscle or stomach cramps
· Nausea, vomiting, or diarrhea
· Brown or dark urine (a sign of dehydration)
Treatment for heat exhaustion
The first strategy for someone who’s overheated is to get out of the heat. If able, move indoors where it is air-conditioned. If you’re on the trail, get into the shade where it is cooler. If you're thirsty, you may be dehydrated, so drink fluids only until your thirst is satisfied. Sports drinks or water with electrolyte tabs are helpful to replace salt and minerals lost with profuse sweating. Remove any unnecessary clothing and place a bandana or buff soaked in cool water on the skin. If you’re near a stream, put your feet in the water to help cool down your body. At this point, it’s likely not safe to continue your hike. Alert someone that you’re in distress and find the shortest way back to a trailhead, preferably with a buddy. Heat exhaustion can quickly progress to a heat stroke; therefore, watch for the warning signs and try to address them before your situation becomes critical.
Heatstroke occurs when your body’s temperature rises to 104°F or more. Heatstroke is a medical emergency. Should you, or someone you’re hiking with, lose consciousness, continue vomiting, or have signs of heat exhaustion that don’t resolve after 30 to 60 minutes of treatment, call for immediate help.
Who’s at risk?
· Adults over the age of 65 and children under the age of 4 have difficulty regulating their body temperature. Thus, these populations are more at risk for heat stress.
· Some medications affect the body’s ability to dissipate heat or stay hydrated. Such drugs are those used in the treatment of high blood pressure, allergies, and psychiatric issues. Anyone taking these medications may struggle with the effects of the heat more. Of course, illegal drugs and alcohol also contribute to dehydration and internal load.
· Obese persons carry a heavier external load, which makes them more susceptible to heat stress.
· Those unacclimated to the environment. If you’re traveling to a climate that is significantly different from the one you’re used to, spend a couple of days acclimating before you venture off on your hike. This strategy is especially helpful if the climate is arid, as you’ll need to spend those days hydrating more than usual.
· Persons in environments with a high heat index. The heat index is the combination of the heat and humidity into a ‘feels like’ temperature. A high heat index means you should limit time spent outdoors.
Wearing loose-fitting and moisture-wicking clothes will help you stay cool. Long-sleeved shirts and pants protect your skin from the sun and sunburn. Sunburn, like any burn, impacts the body’s ability to regulate its temperature, so try to avoid it as much as possible.
Proper hydration is also paramount when exercising and hiking in the heat. For every hour spent hiking in the heat, carry approximately one liter of water. Also, consider setting a watch alarm for 15-minute increments to remind you to take a sip. Water is only helpful if you’re drinking it. Slip an electrolyte tab into one of your water bottles so that you can replace needed salts and minerals as well.
Hike in the cooler parts of the day. Get an early start and take a nap mid-day in the shade. Then venture off again in the cool of the evening. This strategy is necessary for desert climates.
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