Running in the heat and humidity can challenge even the best runners, and Ontario in the summer is all that and more! It’s critical to not only understand the early signs of heat injury, but have a toolbox of strategies to prevent it from happening in the first place.

Whilst our ability to run in the heat is in part determined by genetics and body composition, most runners will naturally slow down once their core temperature gets to around 40 degrees Celsius. It is unclear why this protective mechanism works for most, but fails in others, resulting in heat exhaustion or heat stroke. Some signs of heat injury to watch out for include:

• Confusion

• Nausea and vomiting 

• Loss of appetite

• Rapid breathing

• Racing heart rate

• Headache

• Extreme thirst

It takes 7 to 14 days of heat exposure to plateau in terms of heat adaptation, with the greatest changes happening in the first 4 to 6 days of exposure. Early summer races, particularly shorter, faster efforts where the body’s engine is revving on high, can hit us the hardest: we are often not acclimated for the heat, leaving our lofty goals in a sweaty heap. The best and safest practice is to slow down and reset our expectations while we adjust to the heat and humidity, understanding that adaptations will occur with the right strategies.

How to acclimate to the heat:

• Expose yourself to heat during exercise. Early in the summer, consider changing the time of your run to hit the peak daytime heat.

• One or two weeks of exercising in the heat for about an hour at a time should be sufficient to acclimate.

• Saunas and hot tubs may help if the weather doesn’t co-operate, or embrace the post-run immersion bath. A twenty-minute hot bath right after finishing a run has been shown to be pretty effective for heat adaptation after just six baths.

• Hot yoga is another good option!

• Wearing extra layers when it is slightly cooler can result in heat adaptation by warming your body beyond what is comfortable.

What can you do to maximize your performance in the heat?

• Wear light and pale coloured, loose fitting clothing.

• A white visor is cooler and better than a cap in sunny conditions.

• Pre-cool with iced water, sports drinks or slushies. You can even do a full immersion ice bath or cold shower pre-run.

• Drink to thirst, but don’t over-drink: drinking copious amounts of fluid will not lower your core body temperature, and may risk hyponatraemia. 

• Keep your body wet for evaporative cooling. Grab water at the aid stations and pour over your head and on large body surface areas.

• Wear a buff and wet it regularly to cool your neck.

• Use sunscreen sparingly. Use enough to prevent burning in key areas, but avoid too much as it beads sweat and makes evaporative cooling less effective.

• Find the shade when you run, even if this means avoidingthe shortest tangents on corners.

• Shorten your warm-up in hot conditions so you don’t prematurely elevate your temperature before the start of a race. 

• Ditch the pace goals in the heat. Heart rate is a better judge of effort: if you normally average 140bpm and a 9 minute/mile pace for a long run, stick to 140bpm and just settle into whatever pace comes naturally. Perhaps invest in a good heart rate monitor for summer running.

• Set realistic goals that factor in the heat. Temperature is the most important variable in predicting performance, with around a 10% drop in performance in hot weather versus optimal conditions. No matter how acclimated or fit you are, your performance will decrease in warm and/or humid summer conditions. The key to performing well when it counts is understanding the things we have control over, and those we don’t – so respect the heat, manage the heat, and know when to back off and protect yourself.

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