How to drink when running on hot days?

By David

Yesterday I set out on my favorite 16-kilometer off-road loop. The trail is quite easy; although it requires climbing a few hills along the way, the total elevation doesn’t exceed much more than 400 meters. In spring, autumn and winter, I run this course without water, getting home in less than two hours, and drink at home. Yesterday, however, it was hot, well over thirty degrees Celsius, so I took a small 1/4 liter soft flask filled with water, just in case. And it didn’t suffice! Approaching home, I ran my mouth dry, my tongue stuck to the palate, couldn’t even say hello to a neighbor.

I was quite surprised. Last year I was running in the Atacama Desert, which is said to be one of the driest places on the Earth. Back then, I read the story of Mauro Prosperi. He lost his way during a sand storm in the Marathon des Sables stage race in 1994, and yet he managed to survive for almost nine days with practically no water. So when I got into the desert, of course, I was wondering how long I could run without water. I managed to do just over three hours without any significant problems.

That’s why I was amazed yesterday when I couldn’t run for only two hours, and besides I cheated with the small soft flask. So I flipped through my favorite book Surviving the Extremes to find out. The average person’s body consists of approximately 50 liters of water. However, even the loss of a single liter can allegedly lead to some malfunctions of the body. When losing five liters, fatigue, exhaustion, and dizziness are setting up. With a 10-liter deficit, cramps and visual or hearing impairments can occur. Losing more than 15 liters is according to the book fatal to most people. Even without any activity, we can sweat up to five liters on a hot day. When adding excessive physical activity, we are losing an extra liter or two per hour by sweating.

Thanks to the book, I realized the first mistake I did yesterday. I started my run at around 2 pm, but until then I drank a half-liter of water barely. And two coffees. When intending to run in the afternoon or the evening, we should drink regularly during the day. If not, as in my case, we start the run with all-day liquids debt, which even increases during the activity. My second mistake was that I should have carried at least 3/4 liters of water. Although I probably sweat more, it’s ok to keep running slightly dehydrated and drink at home. And how about the best runners? It seems they drink quite a little. Recently, I read Kilian Jornet’s comment on Instagram on how he eats and what he drinks during races. Here are some interesting quotes from his rather lengthy post: “… I usually only drink water, sometimes I’m switching water and electrolytes. On shorter races (up to 5h) I drink much less, about 250cl per hour maximum, knowing that being a little dehydrated doesn’t affect the performance on short races…”

On long runs, Kilian, however, drinks even less: “… When it comes to long runs or climbs in the mountains where I need to carry everything, these ratios are not possible anymore, when doing a 20 or 40h trip I try to eat a gel (100-200kcal) every 4h and drink about 1l every 5-8h… “It seems almost impossible, but at the end of his post, Kilian explains the trick: “… Before the race I often drink a lot the day before, until I piss a lot and completely transparent, then before the race, I use to drink around 1L between waking up 3h before and the start of the race.…”And how about you and drinking on runs? Which of you has adopted a strategy similar to Kilian?