At the peak of the hottest and most humid season, it is crucial to recognize the signs and symptoms of heat-related illness. While some of our heaviest training and racing is in these conditions, it is imperative we are educated and take the preventive steps necessary to reduce our risk for heat-related illness.
Heat-related illness is most likely to occur in temperatures over 100 degrees Fahrenheit but other factors such as humidity, not being acclimated to exercise in the heat, dehydration, the type and amount of clothing you wear, and lack of air circulation (like riding a trainer in your garage without a fan) can increase risk.
Below are the signs and symptoms for heat exhaustion and heat stroke from the American Red Cross. Some of these symptoms are natural physiological responses to exercise, especially with increased distance and intensity in a single session or race, so it becomes increasingly important to know the other symptoms.
Signs and Symptoms of Heat Exhaustion
Signs and Symptoms of Heat Stroke
Heat illness may lead to heat cramps, which are uncomfortable muscle spasms resulting from dehydration and electrolyte loss due to sweating. While these cramps are typically more prevalent in hot and humid environments, they are not directly linked to an increase in body temperature. If you’re experiencing heat cramps, stop exercise, rest and drink a carbohydrate with electrolyte mix. Taking a salt tablet is not a good idea as this can encourage a loss of water (further dehydration). We need hydration plus electrolytes to rehydrate the body.
Exercising in the heat can feel extremely difficult, especially at first. However, once acclimated, the performance benefits really pay off. We can achieve complete heat acclimatization by exercising for 90 minutes a day over 10 consecutive days in a 30°C wet-bulb globe temperature.1 Once acclimated, continue with exercise sessions lasting 30–120 minutes every 4–5 days until the end of the season. Without regular exposure to exercise-heat stress, full heat acclimation will diminish within a month.1
Use good decision making with your training as you acclimate to the heat, for your safety and to ensure good training. Depending on how high the heat and humidity and how long this season lasts where you train, you may need to consider bringing some of your sessions indoors. With extremely high levels of heat and humidity, the paces and durations you can reach decline. The goal is to ensure you are hitting the intensity levels and durations needed in training.
On extremely hot and humid days, train indoors, train early or swap sessions so you’re hitting the pool instead of running or biking outside. Be sure to stay hydrated throughout the week and during training. Increase your electrolyte intake slightly before and during exercise. For example, drink a Gatorade an hour before your session and consider adding an electrolyte solution to your plain water bottle. We don’t want to excessively add electrolytes, but we need to ensure we are getting what we need.
Do not let yourself be defeated by training in the heat. You will acclimate and see results over time. Be wise in your judgment of when to train indoors versus out. Stay well hydrated, consume more electrolytes on the hottest and most humid days and ensure you are obtaining good recovery. Be cognizant of the signs and symptoms of heat illness for yourself and anyone you may be training with in the heat.
1Pryor JL, Johnson EC, Roberts WO, Pryor RR. Application of evidence-based recommendations for heat acclimation: Individual and team sport perspectives. Temperature (Austin). 2018 Oct 13;6(1):37-49. doi: 10.1080/23328940.2018.1516537. PMID: 30906810; PMCID: PMC6422510.