ISSA SN Chapter 6: Water and Oxygen

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Chapter Goals:

  • Describe and define the main terms associated with the oxygenation and hydration of athletes.
  • Know about balancing water in the body.
  • Find estimates for the hydration needs of athletes.
  • Know the effects of dehydration and relate them to athletic performances.
  • Know what role oxygen plays in the human body.
  • Discuss the nutrients and other nutritional substances related to blood and oxygen flow in the body.


Water and Oxygen are two of the more important nutrients for our health and our performance ability. Research has shown that even small variations in the body’s water balance will negatively affect our performance. Even though these two things are so important, many people take them for granted and neglect them. This will be true for athletes and those that are not athletes. 


Water consumption is required every day for optimal health and solid athletic performance. Hypohydration is still very common among both nonathletes and athletes alike. This is when water intake does not meet our need for hydration. This puts you in a state of dehydration.

Euhydration is a term that means we are adequately hydrated. And then hyperhydration is the opposite of dehydration, and it is when we have too much water in the body.

A Word of Caution

Electrolytes are something to consider when we aim to be euhydrated. 

The things attributed to the daily water balance will be total activities throughout the day, your climate, your health status, the clothing worn, and food consumed throughout the day.  

Athletic Training for Water Conservation

Managing your losses in fluids is a major thing to consider. You may not be able to control the environment you are in for events, but they likely can control the environment slightly when they are training. This is seen in controlling the time of day or the clothing they choose to wear. 

The simple rule of losing fluids is that you should aim to keep your losses below 2% of your total body weight. 

Water and the Athlete

Water is made up of one oxygen atom and two hydrogen atoms. It is used for transporting food materials in the body, and it happens to be where most of the biochemical reactions occur. For the very obese, we see water representing around 45% of total body weight and then up to 70% in lean people. The average is going to be around 60% in the general person. The body parts also vary in their water within. Blood is usually around 83& water, while fat is like 10%. And then we usually have muscle tissue made up of 75% water. So, there is a lot of variation throughout the types of tissues.

Water balance

Water intake and water loss levels affect a person’s hydration status. We intake water when we drink fluids and produce it from food metabolization. 

The major water intakes are metabolic water, liquids, food, and glycogen-bound water. The major outputs will be sweat from the skin, exhaling through the lungs, the kidneys, and then feces from the digestive system. 

Metabolic Water:

This comes from energy metabolism, and it is often not thought about.


This is far from the body’s biggest source of water. This is simply the water we drink. 


Most of the food we take in has some water in it, which varies per type of food, but it is a significant portion of our intake.

Glycogen-bound Water:

This is the water that we store in our muscles that accompanies the glycogen. We store about 3 – 4 ounces of water per ounce of glycogen. 

Skin – sweat:

We lose water through our sweat, which becomes more evident when we do an increased activity like training. It is the cooling mechanism of the body.


Some small water levels will be lost through water droplets in the air we exhale. 

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We filter some water out through the kidneys and then excrete it through urine. This is minimized during activity due to the need for water. 


This is the last major way we excrete water, usually a small amount. 

Hypohydration / Dehydration effects on Performance and Health

A state of hypohydration, having too little water, can severely diminish your performance physically, your functioning mentally, and your control of the motor system. 

When the body loses water, the core temperature increases, affecting all metabolism pathways. When water loss equals 1 – 2 percent of body weight, we see some noticeable reduction in physical performance. In marathon runners, it is not uncommon to see losses as great as 6 – 10% of total body weight through a race. Proper hydration strategies following the event will help to counteract these impaired performance effects. 

Beware the Limitations

There are limitations to the data for hydration, like some saying sweat rates are from 0.3 – 2.4 liters per hour and then other data showing football players having a sweat loss ratio of larger players being 3 or more liters every hour. 

How Much Water Does an Athlete Need?

This amount varies largely based on how hydrated you are at the start, the climate you are in, the duration of your chosen activity, the intensity at which you are doing the activity, and the other activities done throughout the day. When someone is hydrated well, they should urinate around every 1.5 – 2 hours. 

Body Weight Fluctuations for Estimating Hydration Needs

A common approach to finding the need for hydration is to track the body’s weight changes throughout the day. An important part of this is right before, during, and after training, as most fluids are lost then for athletes. 

Daily Guidelines for Hydration Examples

Some examples look at the total daily energy expenditure of athletes. 

2 thousand calories expenditures should take in a minimum of 64 – 80 ounces of water each day. 

3 thousand calorie expenditures should aim to take in around 102 – 118 ounces of water per day.

And so on….

Sources of Water

The quality of water and other beverages should be of some concern to people. There are some major harmful effects of the contaminants found within the drinking water, and chemicals in some beverages will have health-conscious people thinking twice before consuming. Since athletes take in more water than the general population, they may take in more impurities from these drinks.

Hydration with Glycerol: Effective, but Proceed with Caution


Like H2O, it is not considered a nutrient to people, but it is impossible to survive without it. It circulates around the body by first entering the lungs, then going through the bloodstream and to the tissues. 

The Lungs

The lungs are the place where oxygen enters the body. They are two organs in the chest on both sides of the heart. Air is taken in through the breath, the oxygen is removed from the air, and then a transfer happens where the oxygen enters the bloodstream. The limiting factor is the amount of air the lungs can take in.

The bloodstream exchanges carbon dioxide and water for oxygen so that it can then enter the body. 

The air we breathe consists of about 21 percent oxygen and 78% nitrogen, with some other small amounts of gases. 

The lungs do not have their own muscles and instead rely on other muscles to allow air to travel in and out.

The Blood

Oxygen is extracted from the lungs and puts into the blood, which will go to the heart and then be pumped around the body for use. It is the alveoli of the lungs that allow this transfer to happen. 

The Blood Vessels

This is where circulation takes oxygen on its journey. The oxygen gets into the body’s cells with this part of the circulation system.

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Tyler Read - Certified Personal Trainer with PTPioneer

Tyler Read

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