5 Side-Effects of Dehydration: Hidden Performance Killer

There’s no question that dehydration and exercise is a dangerous combination. People often fail to realize that fact. The average person, unlike well-trained athletes and weight trainers, doesn’t understand the sheer importance of proper hydration on exercise performance. So when the average Joe starts a fitness program, he never thinks of water as an essential element. He is probably more concerned with snapping a selfie of his post-workout pump.

Why should you care? You tend to lose more water when you increase activity. So joggers and gym rats are at higher risk of dehydration than couch potatoes. But that’s just one side of the story. Another side has something to with the adverse effects of dehydration on exercise performance.

Here are five things that happen to your exercise or workout performance when you’re dehydrated.

1. You get tired faster

Exercise when done right should boost your energy, not deplete it. But what happens when you’re dehydrated is different. Loss of water sabotages your energy levels.

Many people blame sleep deprivation or inadequate nutrition for sub-optimal workout performance, but they don’t look at the role of dehydration in premature fatigue. Loss of 2% of water in the body can impair exercise performance for a number of reasons. It could be due to decreased blood flow, decreased core temperature regulation1, and increased glycogen use in muscles. These effects are exacerbated by hot and dry conditions2.

2. Your cognitive performance drops

Exercise isn’t just a function of the muscles. Your central nervous system has a crucial role, being the control center that fires signals to your muscles. A decline in cognitive function affects motor coordination and mood.3 Another study also shows that dehydration forces the brain to work harder to achieve the same degree of neural activity.4 This affects visual and spatial processing, executive functions that you rely on unconsciously when you exercise.

Another way that dehydration affects your physical performance is by reducing your ability to concentrate. Concentration is one thing you need to do your exercises properly. Poor concentration leads to bad form, bad execution, and higher risk of injury. Scientists still don’t understand how the loss of water affects executive brain functions. But what’s important to take note of here is that if your brain isn’t at its top shape, everything else suffers, including your ability to finish your reps at the gym.

3. Your mood changes

This side effect is more like an extension of the second problem. Two studies reported the effects of dehydration on the mood, and this adverse effect is seen to a greater degree in women.5 Nonetheless, adverse changes in mood affect motivation, which you need in initiating physical activity. It’s simple. If you don’t feel like running or doing push-ups because you’re dehydrated, you either skip the exercise or do it poorly. Sometimes you just don’t feel like going to the gym, let alone finishing your sets. And you don’t know why. You had a good night sleep. You don’t think work is stressful. Maybe you just need to up your water intake.

4. You lose endurance

Runners usually notice this dehydration-induced loss of endurance. Premature exhaustion, decreased ability to regulate core temperature, and decreased maximal aerobic power occur when you lose as little as 2% of fluids. Hot environments worsen the effects of dehydration, which also raises the risk of heat exhaustion. It’s a terrible feedback loop, one which in a study was found out to reduce endurance time from 121 minutes to 55 minutes.6

5. Your muscles become weak

Your muscle tissue is 79% water.7 In other words, a huge portion of water that you drink goes to your muscles. You better know that the most important substance for muscle building is not protein, but water. For most people, muscle power becomes noticeably affected when you’re 3% dehydrated, and that impacts exercise performance. If you’re training for strength, dehydration can weaken your muscle enough to hamper your progress. Try working out dehydrated and see if you can finish with similar reps that you normally could when properly hydrated.

The thing about dehydration is people don’t notice it. Three out of every four Americans may be chronically dehydrated.8 Most of them don’t even realize they are. While dehydration affects exercise performance, exercise also raises your risk of dehydration. This negative feedback loop can lead to further health maladies unless corrected, and fixing it is as easy as drinking fluids before and after your workouts. Make sure you properly hydrate throughout the day perform your best physically and mentally.

Thoughts or comments? We’d love to hear from you!


  1. http://www.sciencedirect.com/science/article/pii/S1095643301002744
  2. https://www.ncbi.nlm.nih.gov/pubmed/10198142
  3. http://ase.tufts.edu/psychology/spacelab/pubs/DAnciEtAlHydrationPMS_2009.pdf
  4. https://www.ncbi.nlm.nih.gov/pubmed/20336685
  5. http://psychcentral.com/news/2012/02/20/dehydration-influences-mood-cognition/35037.html
  6. http://www.humankinetics.com/excerpts/excerpts/dehydration-and-its-effects-on-performance
  7. http://water.usgs.gov/edu/propertyyou.html
  8. http://www.medicaldaily.com/75-americans-may-suffer-chronic-dehydration-according-doctors-247393

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