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This is article is not intended to be
a complete discussion on nutrition. Rather it is to set-up the reader for an
article on bioenergetics. The main goal of this article is to discuss the role
of each of the nutrients in body. As such, the article gives a simple
discussion on each nutrient and its role in exercise. It is recommended that
one should consult with a licensed nutritionist on proper nutrition practices.
The
last nutrient to be discussed is water. Water is the most abundant and
important inorganic compound in living materials. It makes up 60% to 80% of
living cells. (3) It also makes up 40% to 70% of body mass (2, 4). It also constitutes
65% to 75% of muscle, and 10% of fat mass (4).
There
are two main water compartments in the body, intracellular and extracellular.
Intracellular water is the water within the cell itself. It represents about
62% of total body water. Extracellular water is the body’s water that flows in between
the microscopic spaces between the cells. Extracellular water also makes up
blood plasma, which accounts for about 20% of extracellular fluid. About 38% of
total body water is extracellular. (4)
1. High heat
capacity: Water has the ability to absorb and release heat before changing
temperature itself. This helps prevent any sudden changes in body temperature
from external factors such as the sun and wind. It also serves the same purpose
internally, preventing a sudden rise in temperature due to physical activity.
2. High heat
vaporization: This is beneficial during sweating response. When water changes
to gas, it transfers large amounts of heat energy to the environment. It takes
a large amount of heat to disrupt the hydrogen bonds that hold the water
molecules together.
3. Polarity/Solvent
Properties: Water is considered the universal solvent. It is also a suspension
medium for both organic and inorganic compounds in the body. Biological
molecules react chemically in a solution, and most chemical reactions in the
body depend on waters solvent properties.
4. Reactivity:
Related to number three above, water serves as an important reactant in many
chemical reactions. For example, when water is added to the basic components of
food when they are digested. Such a reaction is called hydrolysis. When
carbohydrates and protein are formed from smaller components, on the other
hand, water is removed. Such reactions are then called dehydration synthesis.
5. Cushioning:
Water forms a resilient cushion around certain organs that helps protect it from
physical trauma. The fluid surrounding the brain, the cerebrospinal fluid, is
composed mainly of water.
Water/Fluid
Balance: (4, 5)
In
a thermo neutral environment, the body needs to take in at least 2.5 L daily. According
to Mcardle et al, water intake is divided between water (about 1,200ml), food
(1,000 ml), and metabolism (350 ml). This equates to about 2,550 ml.
Based on
the above, approximately 60% of our water requirement is supplied by fluids we
drink. The foods we also eat contain some water and this supplies approximately
30% of our daily intake. The remaining 10% water requirement is supplied from
the body’s metabolism.
Water
output is the same as intake. This is assuming that the person is in a thermo
neutral environment and practices proper hydration. The human body tends
excrete water at a rate of 2.5 L per day through the urine (1,250 ml), feces
(100 ml), skin (850 ml), and lungs (350 ml). Again, about 2,550 ml daily.
About
60% of water loss when at rest is through the urine. Water loss through
breathing is approximately 30%. This also called insensible water loss. Under resting
conditions, we still lose about 5% of our body’s water through sweating,
insensible perspiration. This is also considered with the insensible water loss
mentioned earlier.
·
Intensity of the physical activity
·
Environmental temperature
·
Relative humidity
Although
the above-mentioned factors affect water loss a great deal, it should also be
noted that water losses through sweating even in water environments happen.
The body
can lose up to more than a liter of water during exercise in a hot and humid
environment. A separate article to discuss in detail the effects of dehydration
and it’s effect on exercise performance will be forthcoming.
Basic
Recommendations for Water Intake: (1, 2)
The
basic recommendations for an average adult is about eight glasses (8-ounce
glass) per day. As per the Food and Nutrition Board of the US, to maintain
adequate hydration, the average male should take in about 3 L daily, and 2.2 L
daily for women. This takes into account the amount of water lost through the
urine.
Beverages
containing caffeine should be limited to about 3 per day. Coffee, tea, and
softdrinks should not be substituted for drinks that contain nutrients, such as
fruit juices.
Bibliography:
1. Corbin, Charles, Gregory Welk, William Corbin, and Karen Welk “Concepts
of Fitness and Wellness: A Comprehensive Lifestyle Approach 9th
edition” 2011
2. Fahey, Thomas, Paul Insel, Walton Roth “Fit and Well: Core Concepts and
Labs in Physical Fitness and Wellness 9th edition” 2011
3. Marieb, Elaiane “Human Anatomy and Physiology” 1989
4. Mcardle, William, Frank Katch and Victor Katch “Exercise Physiology:
Nutrition, Energy, and Human Performance 7th edition” 2010
