Hydrating properly is a huge issue for runners. Dehydration and heat stroke are just a couple of problems with being lax about your water intake during a run or other exercise. It’s pretty straight forward that you need more water when your running in the heat, but what about running in humidity. Maybe this is a no brainer for those who live in a humid climate.
For those of us who don’t (me), at first glance, it seems like maybe you don’t need as much since there is so much water in the air already. But, running in humidity actually requires more water than running in dry heat.
Our bodies cool themselves through sweating. In order to sweat we need water and electrolytes. The more we sweat, the more we need. Pretty simple. To complicate matters just a bit, intense exercise causes your body temperature to go up, which then requires more sweating. Remember the last time you had a fever? You didn’t even have to move to sweat.
When you are running (or sweating for any reason) in humidity, the sweat doesn’t evaporate, which is what allows your skin to cool. Because it doesn’t evaporate, it continues to produce more sweat to attempt to cool you down.
Prehydrating is important whenever you are going to run in the heat, but particularly when you combine heat and humidity.
Dehydration progressively decreases your pace by two to three percent for every one percent loss in body weight. Your blood volume decreases when you don’t have enough water. This makes it so your body cannot fuel your muscles properly and thus slows you down. Dehydration also slows recovery because your body cannot get rid of waste products it produces.
Overhydrating can also be dangerous. Hyponatremia (low sodium) is a serious condition, but it’s easily avoided. If you are exercising for over an hour, make sure you are ingesting some electrolytes. Most of the time, I use salt tablets. They are easy to carry and take during a run. I will also use Heed if I’m struggling to maintain that balance. Cravings for salty things, a decrease in pace, cramps, a foggy mind, and sloshing stomach are good indicators you’re electrolytes are out of balance.
Like with any aspect of running, everyone is different. Runner’s metabolisms process water at different rates. In order to determine how quickly your body loses water make sure you are hydrated before exercise, weigh yourself before you go out, and weigh yourself again when you return. Drink water over the next few hours until your body reaches the weight it was before you exercised. This will give you an idea of how quickly your body metabolizes water.