THERE ARE THINGS we runners can do to avoid the heat. The treadmill next to an air conditioner comes to mind. As does running in the wee hours of the morning or evening rather than at high noon. But what’s a runner to do when the mid-day run calls and the heat of the sun beats down?
Research has long searched for ways to improve time to exhaustion, lessen athlete’s internal temperature, and improve overall performance in the heat. For starters, I always recommend athletes arrive to the starting line well hydrated and you can do this by really honing in on fluid intake in the days and hours leading up to the big event. Clearly, you’ll want to avoid over-hydration or water intoxication – occurring when your intake of H2O overwhelms your intake of electrolytes. Avoid disaster by sipping on fluids when thirsty and consume fluid-filled fruits and veggies as you prepare for your run. According to the American College of Sports Medicine, aim for approximately 30mL of fluids per 4.5kg of body weight at least four hours prior to exercise. If you still feel thirsty two hours prior, 30mL per every 7-9kg of body weight should quench your thirst. If that doesn’t do it, the National Athletic Trainers Association adds that 200-300mL of fluid 10-20 minutes before exercise can help. Just make sure to leave time for a bathroom stop before heading out the door. One more thing; if you’re really hitting those fluids hard, opt for some sports drink or a beverage with some electrolytes rather than plain water as you’ll need the extra salt and potassium as the kilometers fly by.
But what if you’ve checked all the hydration boxes and are still falling victim to the heat? You might try pre-cooling. That’s right, you can cool down before you heat up and by doing so, you’ll start your run with a lower core temperature and improve your submaximal running time in the heat. There are a few ways to pre-cool; ice slurry ingestion and cold-water immersion are two of the most common (since not every running has access to a walk-in freezer). Luckily, ice slurry ingestion has been proven to be comparable to the inconvenient cold-water immersion. One study comparing the effects of cold water immersion, warm fluid ingestion, or ice slurry ingestion, found that runners who consumed the ice slurry prior to a hot run took longer to fatigue, had lower rates of perceived exertion, and were able to withstand a higher body temperature before they called it quits. Another study looked at the performance benefits of ice slurry ingestion compared to the effects of drinking a thermoneutral beverage (a control) or simply swirling the slushy and spitting it out. Compared to the control, drinking either the slushy or the mouthwash resulted in performance improvements. However, the greatest gains (lowered rate of perceived exertion, improved thermal comfort, and overall improved performance) were seen when the slushy was actually ingested versus swished and spit.
So, you might be wondering what’s the best way to consume such a slushy or slurry before heading out the door? Since it takes quite a while for a sports drink to freeze (thanks to the sodium content), you can easily make a quick slurry by pouring 180mL sports drink and 1 cup ice into a blender, mix it up, and consume it 10-20 minutes before running.