Why We Should Hydrate?

It is common knowledge that we need water to live. Even from weight loss and muscle gain perspective we know drinking water or hydration is essential. Yet when it comes to fine detail like, why we need it, what benefit will it have, and timing of drinking water is often overlooked. Just by saying "hydration is important" may not be convincing and I feel the same way. So, let’s start the hydration journey with understanding of what our body use water for.

Water in Our Body

Adult human body is made of 60% water. It is also important to know that there are two major locations that we need to be familiar with. Intracellular fluid (ICF) which consists of two-third of water in the body, and extracellular fluid (ECF) which consists of remainder of one-third of water. About 25% of ECF is for blood/vasculature and 60% of ECF is interstitial fluid, which is fluid found in the space of the cells.

Water composition in our body may change due to our body composition. Muscle is about 75% water and fat tissue is 10% water. Therefore, comparing person who has 10% body fat to 30% body fat the water contents in our body will be different.

Importance of Tonicity

Tonicity is a measure of concentration in solution compared to another. For example, if we place our blood into different concentration of solution what will happen? It is important to remember that our body strives to maintain equilibrium. With blood example, there are 3 things that can happen.

One is called isotonic where both solutions, blood, and another solution, are equal, therefore there will be no changes.

Second is hypertonic where concentration of solution that red blood cell is in is higher. When this happens, because water content will be higher in the blood the water within the blood flow into the solution, which will shrivel the red blood cells.

Third is hypotonic where solution has lower concentration than the red blood cell. When this happens, because water content will be higher in the solution the water in the solution will flow into the blood, which will swell the red blood cells and may eventually rupture.

Because pure water has tonicity of zero, when infused it to vascular system the cells in the body would rupture. Which means when giving IV in hospital, it is important to give solution that is close isotonic meaning closer tonicity to the blood. However, depending on the condition, solution can be hypertonic or hypotonic.

Dehydration

There are two different types of dehydration. The term dehydration that we commonly use is defined as a loss of water without losing sodium. Because of water content is being lost concentration of solution or tonicity will increase. Since majority of water is in ICF, primary pure water loss affects intercellular volume rather than circulatory or blood volume.

Second type of dehydration is volume depletion or hypovolemia. This primarily refers to loss of extracellular volume as well as sodium content. Best example is sweating which is least extreme case for hypovolemia. When you sweat not only, we lose water but also electrolyte as well. Therefore, when you exercise and sweat a lot or when you are in very dry and hot environment without rehydrating with water and electrolyte you may experience lightheadedness due to loss of water, electrolyte which can lead to loss of blood volume.

Ways we can lose water is by urine, sweat, and respiratory surface. Urine, probably is, the most common way that the water leaves the body. This is due to filtration mechanism by kidney. We also lose water from skin by sweat. When you think of surface area of skin, sweat can significantly decrease water volume especially when you are active and/or in hotter environments. Least commonly known way is respiratory surface. When you remove lungs and spread it on the floor, it can cover tennis court. Lungs facilitate gas exchange mainly with oxygen and carbon dioxide. Since the final common pathway of metabolism is carbon dioxide and water, we are breathing out carbon dioxide and vapor. Which means when the air is hotter and drier more of them are being exhaled. So when you are on the plane it is important to hydrate since the air is much drier.

There are substances such as caffeine and alcohol that can speed up the dehydration. They are both in a category of diuretics, which means it forces you to pee. Caffeine usage is common prior to exercise either with coffee or pre-workout. Although there are benefits, however, it is important to hydrate frequently during the workout because you will be losing water faster than usual. If you consume alcohol, it is beneficial to drink water after each drink.

Dehydration and Effect on Exercise Performance

When monitoring exercise performance there are two major variables, cardiac output and VO2. Cardiac output is how much volume of blood can the heart pump out per minute. VO2 is how much oxygen can be utilized. Although VO2 is very important metric in physical performance, however, it doesn’t seem to get affected by dehydration.

Cardiac output, however, will have impact by dehydration. When heart is pumping out more blood during exercise, heart must receive that much volume of blood. Since the blood volume can decrease when we are dehydrated (i.e., sweating), heartrate will increase to maintain the level of performance.

For example, if you donate blood prior to your workout, because of the blood volume decrease your exercise heartrate will go up even when you are exercise intensity is at the level you are used to. This is same when you are exercising in a hot and humid environment where the body is forced to sweat. Therefore, in those two situations it is a commonly advised to hydrate more frequently.

Another effect of dehydration is when losing volume and not replacing it may not be able to replace glucose as well. This may sound great for those who are wanting to lose fat, but it is the opposite. While we are exercising, whether it is lifting weight, hiking, gardening, playing sports, our body needs glucose replenishment to produce more energy or ATP (adenosine triphosphate). Glucose is the substrate for ATP. Even if we take glucose supplements such as glucose gel or even fruits, the water itself is not replenished, therefore, body cannot facilitate absorption of those nutrients including electrolytes.

Although dehydration is not the only factor that decline your physical performance, however, it is one of the issues that we see often.

Hydration with Supplements

Currently we have various product options with sports nutrition even with replenishing electrolyte and glucose. Although it may be challenging to monitor, paying attention to tonicity of solution is important as we’ve discussed earlier.

Things we need to keep in mind is what we are losing while exercising and what is your purpose of exercise. When we are exercising, we do sweat. Depending on individual, amount we sweat may vary, however, we still do sweat. Through sweating we are losing both water and sodium. Needless to say, those are content that need to be replenished. Using electrolyte powder mixed with water can be beneficial. Supplement in gel form, however, may be enough to replenish glucose and electrolyte but not water.

If you are working on fat loss, using powder mix with sugar may not be ideal for the body lose opportunity to replenish muscle glycogen through fat. This is same with post workout fruits such as banana and apple for its high sugar content especially fructose. If you need to replenish electrolyte and water, during and after your physical activity use the electrolyte powder with no sugar mixed with water. Lightheadedness we may experience during exercise is not due to glycogen or glucose depletion but more towards dehydration, depletion of minerals and decrease in oxygen saturation level due to intensity and duration of the exercise. Therefore, when you do get lightheadedness during the physical activity, you should get hydrated with electrolytes then work on deep breathing.

If your goal is to improve performance (strength, endurance, etc.), what you will replenish with will be determined by duration and intensity of the activity. Lets say if you are planning on lifting weights for 2 hours. Then you may need at least 20oz of water with mixture of glucose and electrolyte to maintain strength and cardiac output during the exercise. We do see some people eat banana during exercise, however, if you are exercising your digestive system is not ready for sympathetic nervous system is the dominant. Therefore, sports drink with sugar and electrolytes will be more suitable for it can be absorbed. Essential amino acids mix can also be helpful in sustaining strength during your physical activity.

When choosing electrolytes, more than potassium, sodium replenishment is important because that is what you sweat out. Potassium is important and popular mineral to avoid muscle cramp, however, can be deadly when over consumed.

Primary Hydration is Water

Although using supplement mix to maximize benefit of hydration and improve on flavor in water is great, however, the primary hydration should be with pure water. This is because the blood is 90% water

You can get water from eating vegetables, fruits, soup and so on, however, main source for hydration should be pure water to balance the tonicity within the blood.

Ideal timing of drink water are:

• Immediately after waking up

• Prior to consuming food (including snack)

• Before exercising

• Before Bedtime

Hydration is most simple form to improve our physiological functioning. If you are struggling to get hydrated, see if you can start from drinking a glass of water prior to eating any food.

Kota Shimada