The weather has finally turned warmer in Maine. We've skipped spring this year and plunged right into summer, with some brutal heat and humidity already so early in the season. Every year, I need to acclimate to the warmer temperatures on my runs and the means, in part, looking at my hydration strategies.
The consequences for getting it wrong in the summer are quick and severe: GI problems hit me hard and fast in heat and humidity. Over the years I've found some relationships between the weather, my rate of exertion and the amount of time I'm spending on my feet that help me to plan my hydration. While fluid volume is certainly a part of my strategy, I take a much closer look at whether I need water, carbs or electrolytes, and whether I need to combine or separate my consumption of those three.
Water. I'll just drink plain water if I'm looking at a hot 5-10k effort or a less intense run of an hour or two in moderately warm temperatures. If you are generally eating and hydrating well during the rest of your day, there's generally no need to drink anything more fancy than water for these efforts. Longer or more intense efforts can require some mid-run calories to keep up your intensity: I generally prefer some easy-to-digest real foods or even a gel in these circumstances, whatever my stomach can tolerate that day. I won't generally even take in nutrition in a run of less than an hour, drinking just to satisfy thirst or, in a hot 5k, to help stay a little cooler.
Carbs. In longer efforts, especially when it's hot and sticky, it can be nice to drink your calories. You're going to drink plenty anyway, so it keeps your nutrition in line with your hydration. During longer, hotter efforts, I feel incredibly weighed down by solid foods, even my beloved Swedish Fish. I will carry flask of Tailwind or Skratch from the outset, or add stick packs to a bladder or flask if I have started with water and food but my stomach sours mid-run and I need more calories in order to persist. If I am not particularly concerned about my electrolytes, I'll indulge in Coke or ginger ale at an aid station. Think you don't love the flavor of warm, off-brand cola? You've just never been in the woods long enough to see the light.
Electrolytes. Sometimes I am not running far enough to justify the calorie intake of of a sports drink, but my sweat rate in the heat will deplete my salt and potassium. Sometimes I have been out long enough in the heat, carefully balancing my water and nutrition but I still get that prickly feeling on the back of my neck that starts when my electrolytes are out of whack. In either case, it's time to add electrolytes to my water intake without consuming additional calories. A product like Nuun will pace your electrolyte consumption with your hydration, which is easy on short, hot runs. An S!Cap will offer a quick, radical change to my electrolyte levels, which must be carefully matched with water consumption: too much, and I don't benefit enough from the electrolytes to begin taking in food again, but not enough, and I wind up with another version of the GI cramping I was trying to avoid.
This takes some trial and error. I've sagged in hot races when I didn't carry water to hydrate between aid stations. I've taken too much water, drinking to stay cool, and learned about hyponatremia during an incredibly close call; conversely, I've not had enough to drink after an S!Cap and paid that price. I've used sports drinks that were too rich in carbs that just made my GI tract revolt, which makes my dehydration worse. Everyone has a learning curve, separating out water, carbs and electrolytes, but with every mistake you learn more about your body and how to manage the situation better next time. I still don't expect to manage them perfectly every time, but I have a better array of strategies, and I find that now I worry about my hot, sticky runs far less than I used to.