By Douglas Holl, USAPHCJuly 18, 2019
ABERDEEN PROVING GROUND, Md. -- For many runners, slogging along in the hot sun is a quick way to shut down a good training run. Before heading to the shade, keep in mind that the best training involves running in conditions one may face in actual competition. Although some runners may be hoping for a cool and cloudy day for the Army 10-miler in October, acclimating to the summer heat can provide a competitive edge on race day.
"It is important to acclimatize your body to the heat," said Dr. Alexis Maule, a Defense Health Agency epidemiologist who works at the Army Public Health Center. "Start your training with short distance runs and slowly work your way to longer time and distance spent running in the heat. It can take several weeks for your body to adjust to training in the heat."
Maule recommends avoiding running in the middle of the day when the sun is at its peak.
"If possible, train early or late in the day to avoid the hottest times of the day or find a running route that has plenty of shade," said Maule. "You will get the same benefits of the aerobic exercise while avoiding unnecessary sun exposure."
Maule recommends runners use sunscreen and eyewear that blocks UV rays to provide protection from the sun.
"Sunburn is the most common sun exposure risk runners face during training and competition," said Maule. "Sunburn inhibits the skin's ability to release body heat, which increases the risk of heat illness. High heat and humidity are also environmental risks that runners face during training and competition. Repeated sun exposure can also lead to skin cancer."
Maule recommends runners balance the goals of comfort by having loose, breathable clothing, which is important for protecting them from environmental hazards such as sun exposure.
One of the dangers of running in the sun is heat illness, which refers to a range of conditions which includes heat cramps, heat exhaustion and heat stroke. Heat stroke is the most severe and requires immediate medical attention. Runners may develop symptoms including light-headedness, dizziness, fatigue and muscle cramps.
There is no specific time of onset for heat illness symptoms, said Maule. The timing of symptoms can depend on many factors, including the outside conditions (temperature, humidity, wind and direct sun exposure), the intensity of the workout, and the physical fitness of the runner as well as their intake of fluids, electrolytes and calories before, during and after a run. When enough of these factors combine, runners can lose the ability to regulate their own temperature. Immediate cooling are the two most important words to remember when heat illness is suspected.
"If you are on a training run, find a shady area to rest and remove extra layers of clothing," said Maule. "If water is accessible, take sips of cool water and splash water on your head, neck, arms and legs."
To avoid dehydration, runners might have to make themselves drink when they are not thirsty," said Joanna Reagan, registered dietitian at the Army Public Health Center.
"It doesn't take much water loss for your performance to suffer," said Reagan. "With only 5 percent body weight of water, your speed and concentration are reduced. It doesn't matter how fit you are, what your body composition is, or how old you are, you can easily become dehydrated. It can happen quickly when you are physically active, especially in extreme climates."
For longer runs, Reagan recommends runners try different systems to determine what works best for them, such as a handheld running bottle, a waist belt or a running hydration vest.
"It is a good idea to drink water or fluids every 20 minutes," said Reagan. "If you are out for less than hour, then water is the best choice. If you are running longer than an hour then you are losing electrolytes and if you lose too many electrolytes, your performance can suffer."
Reagan says the key for replacing electrolytes is sodium and potassium along with calcium and magnesium. The easiest way to do with is with an electrolyte replacement sport drink. There are also powders or tablets that can be mixed with water runners can carry with them on their route.
The first signs and symptoms for dehydration are a slight headache and dark colored urine, said Reagan. As dehydration worsens, symptom are thirst, muscle cramps, fatigue and decreased heart rate. Runners need to listen to the signs and symptoms of their bodies and slowly sip on a fluids to help re-hydrate.
"Water, sports drinks, diluted fruit juice, milk and milk alternatives are good choices," said Reagan. "Don't forget about food choices high in water content such as fruit, vegetables, soups and yogurt."
Drinking too much plain water or not eating enough sodium can result in hyponatremia (low sodium levels in your blood), said Reagan. This can be very serious, if not treated. Women can be at greater risk than men of developing exercise-associated hyponatremia. The signs and symptoms include headache, vomiting, swollen hands and feet, confusion and wheezy breathing.
"During exercise, limit fluids to four cups per hour or six cups in hot weather to avoid hyponatremia," said Reagan. "Do not drink more than 12 quarts per day."
The APHC Heat Illness Prevention and Sun Safety page has information and resources on prevention, detection and treatment of heat illness: https://phc.amedd.army.mil/topics/discond/hipss/Pages/default.aspx.
The Army Public Health Center focuses on promoting healthy people, communities, animals and workplaces through the prevention of disease, injury and disability of Soldiers, military retirees, their families, veterans, Army civilian employees, and animals through studies, surveys and technical consultations.