As runners, we all know that we need to be hydrated, but what does that really mean, and what happens if we fall short?
In this article, I’m going to dive into exactly what happens — both internally and externally — when we’re dehydrated. In addition, I’m going to examine the best ways to spot dehydration, and, most importantly, how to stay hydrated so that you don’t have to worry about getting dehydrated in the first place.
What Is Dehydration?
Dehydration occurs when our bodies lose vital electrolytes through sweating, which is essentially the body’s built-in cooling mechanism.
The American Chemical Society describes electrolytes as salts, ingested mainly through food, that dissolve into positive or negative charges. And in the scope of athletic performance, the most crucial electrolytes are potassium, sodium, calcium and magnesium.
So why are electrolytes so important for runners? Electrolytes control water movement in the body’s cells, as well as your body’s nerve impulses. This means these salts play crucial roles in brain function, muscle firing and even the beating of your heart.
During a training session, the following things happen when we lose these electrolytes:
- Muscle fatigue sets in earlier
- Heart rate increases
- Performance decreases
- Mental clarity suffers
In addition, dehydration impacts recovery long after the run or training session. Because it impedes your muscles’ recovery process, dehydration during just one workout can actually hinder your workouts for the few days after that. Since your muscles will not have fully recovered, performance may continue to suffer.
Signals of Dehydration for Runners
The most well known indicator of dehydration is thirst. As a general rule, if you’re thirsty, you are likely already dehydrated. In addition, dry mouth, dry eyes and even dry skin can also serve as signals. Look out for headaches and nausea as well!
Other, lesser known signals include mental fatigue, a lack of motivation and increased heart rate while at a normal run pace.
Additionally, over-sweating and under-sweating can both indicate dehydration. Over-sweating is your body’s way of warning you that you are expending energy and losing electrolytes that need to be replaced.
Under-sweating is a bit more complicated of a signal. Absent sweating in conditions you would normally sweat in, also known as hypohidrosis, often indicates heat exhaustion, which can be partially, or fully, caused by dehydration. (1)
Heat exhaustion refers to any sort of mild heat-related illness. Nausea, vomiting and weakness are all symptoms of heat exhaustion that occur when your body fails to cool itself through sweating. Extreme heat exhaustion is called heat stroke and indicates your body’s total failure to regulate its temperature. Symptoms of heat stroke include high fever, rapid heart rate and loss of consciousness.
While dehydration is not always the cause of under-sweating, it is likely a factor if you are under-sweating during a training session.
Because of this, be sure to take note of your mid-training sweat levels. Hydrate often to replenish electrolytes if you are over-sweating and find a way to externally cool down your body’s temperature if you are under-sweating.
Dehydration looks different on everyone, so you likely won’t have all of the symptoms mentioned above if you do, in fact, get dehydrated. As a result, it’s important to know your own body and find out what your body’s response is to the loss of those vital electrolytes.
Hydration Tips for Runners: How to Avoid Dehydration
Daily hydration is the easiest way to avoid all of the above symptoms and signals.
Experts recommend drinking 8–10 glasses of water per day, every day, while also incorporating foods with high water content into your diet. Cucumbers, watermelon, spinach, iceberg lettuce, cauliflower, broccoli, radishes, tomatoes and green peppers are all great options to help you stay hydrated.
In addition, you should find a good hydration product that you can use before, during and after your training sessions to replenish any electrolytes your body loses.
A hydration product provides key electrolytes (sodium, potassium, calcium and magnesium), as well as crucial minerals, that are typically lost through sweating during a run or workout. Sports drinks are the most common hydration products, however, a lot of them can be extremely high in sugar, which can have other adverse effects on your body.
When choosing a hydration drink, look for a product that has between 250–350 grams of sodium and under 10 grams of sugar. Be sure to hydrate with this every 20 minutes or so while training, as well as before and after the session.
We at The Run Experience love S.O.S, because it’s medically formulated to be similar to an IV hydration supplement that a patient would receive in a hospital. It also tastes good and is high in sodium but low in sugar.
It can take up to 48 hours to recover from dehydration, but you can avoid it completely by simply drinking enough fluids throughout the day and making sure to hydrate with a high-quality product while training!
Hydration Tips for Runners: Race Day Prep
Remembering to hydrate during your workouts and drinking water throughout the day are all steps in the right direction for a hydrated race.
However, you should be sure to use all of your training sessions as hydration test runs for race day! If hydrating every 20 minutes on your long run left you with a headache or another dehydration symptom at the end, that’s a good sign that you may need to bump up your efforts and try hydrating every 10 or 15 minutes on your next training run.
Give yourself an honest evaluation of how your hydration program works after every training run so that you know exactly what your body needs during your big race.
Additionally, be sure to check the course and weather forecast before a race. Dehydration is one of the worst surprises to have on race day, but doing a little advance prep can help you avoid dehydration altogether.
Checking out the course ahead of time can tell you how many aid stations there will be, so you can pack your own hydration products accordingly.
Also, if you know the race is going to be hilly, hot, largely in the sun, or heading into the wind, you can try to train in those conditions so that you know what it takes to keep your body hydrated for optimal race performance.
As you can see, staying hydrated as a runner is really just a matter of knowing your own body. Monitor your symptoms, and use trial and error to see what works for you.
To keep your body hydrated on a regular basis, drink water throughout the day, and drink a well-formulated hydration supplement to replenish any lost electrolytes during your training, and you should be good to go.
Holly Martin is a San Francisco-based running coach and personal trainer. With a 20+ year background in dance, Holly brings a strong focus on technique and mobility to all of her coaching. Currently, she trains clients at Midline Training and Nfinite Strength, and coaches online with The Run Experience, an online training community for running training programs and workouts. She enjoys writing tips for running that help you become a better, stronger and injury-proof runner.