Dehydration caused by exercise

Greetings and thank you for taking the time to read my blog post about dehydration caused by exercise.

As a certified personal trainer, I have seen many people neglect their hydration needs during workouts, which can lead to serious health risks. In this post, I will explain what dehydration is, why it happens during exercise, how to recognize it, and why staying hydrated is crucial for athletic performance and overall health.

What is Dehydration?

Dehydration is when your body loses more fluids than it takes in, resulting in an insufficient amount of water to perform essential functions. During exercise, the body sweats to regulate its temperature, and if we do not replenish our fluids, we risk becoming dehydrated.

Why hydration during exercise is important

Staying hydrated during exercise is vital for optimal athletic performance and overall health. Proper hydration can help prevent fatigue, dizziness, and cramping. It also helps regulate body temperature, enhances nutrient absorption, and supports the function of vital organs.

Mistakes You See in the Gym

One of the most common mistakes I see in the gym is people coming without a water bottle or with a small one that is not enough to keep them hydrated during their whole workout. Another mistake is that people who do cardio tend to drink too little water, leading to long-term health risks associated with chronic dehydration. Lastly, some people run out of water during exercise, thinking they can get hydrated later, but this is not the case. Dehydration can cause syncope (fainting), which can be dangerous, whether in the locker room or driving home. It is vital to drink when your body needs hydration.

How to Prevent Dehydration

Preventing dehydration is simple. The recommended daily fluid intake for active individuals is around 64-80 ounces of water per day, and more if you are exercising in hot or humid environments. However, fluid intake should be tailored to individual needs based on factors such as body weight, exercise intensity, and sweat rate. When choosing the right type of fluid for hydration, it is best to opt for water or sports drinks containing electrolytes that replenish lost nutrients.


There has been a lot of research conducted on dehydration caused by exercise.

One study, published in the Journal of Athletic Training, found that even mild dehydration can negatively impact athletic performance, particularly during endurance exercise.

Another study, published in the International Journal of Sports Medicine, found that dehydration can lead to decreased blood flow and increased heart rate during exercise, which can lead to decreased performance and increased risk of injury.

These studies and many others confirm that drinking enough water during exercise is not just a theory, it's a scientific fact. 

The American Council on Exercise recommends that active individuals consume 17-20 ounces of water 2-3 hours before exercise, and then continue to drink water during and after exercise to replace fluids lost through sweat. Other fluids like sports drinks and coconut water can also be beneficial for hydration, but it’s important to choose the right type of fluid for your specific exercise needs.

So, next time you hit the gym, make sure to bring a water bottle and drink enough fluids throughout your workout to avoid the negative effects of dehydration on athletic performance and overall health.

Graphical representation showing the key elements involved in regaining and keeping proper fluid balance after physical activity. ECF stands for extracellular fluid.
Gethin H. Evans, Lewis J. James, Susan M. Shirreffs, and Ronald J. Maughan School of Healthcare Science, Manchester Metropolitan University, Manchester, United Kingdom;  School of Sport, Exercise, and Health Sciences, Loughborough University, Loughborough, Leicestershire, United Kingdom; and  School of Medicine, University of St. Andrews, St. Andrews, United Kingdom



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In conclusion, staying hydrated during exercise is essential for optimal performance and overall health. Neglecting your hydration needs can lead to serious health risks, such as dehydration, which can cause syncope, fatigue, and cramping. As a certified personal trainer, I always remind my clients to bring a water bottle and drink regularly during exercise. If you see someone working out without water, don’t hesitate to remind them to stay hydrated. Let’s make hydration a priority and stay safe and healthy during exercise!