How
important is water for our body? It
is essential for life. Through respiration, sweating, urinary, and fecal
output, we lose water in each and every part of our day. Through exercise, we
only accelerate our fluid loss and rehydrating becomes that much more important
to prevent cramping, dizziness, and even death if adequate fluid is not
replaced in the body.
In
our body, about 60% of our total body weight is water and is soaked up by each
of our millions and millions of cells.
For example, a 100 lb. female holds 60 lbs. of water. Our body composition
determines how much total body water we carry.
Each of these contain…
Muscle cells = 75% water
Fat cells (adipose tissue) = 25% water
Bone = 22% water
Blood = 83% water
The leaner an individual is the more
water they are going to carry, and the more water they will need to replenish
through their daily lifestyle. No matter what your body composition, all this
water in the body has many important jobs…
1.
A Transporter –
transports nutrients to cells and carries waste products away from the cells
2.
Role in Growth –
water is important in the synthesis of proteins, glycogen, and other
macromolecules
3.
Lubricant – water
lubricates joints and acts as a shock absorber for the eyes & spinal cord
4.
Temperature Regulator
– body water content and fluid exchange regulate body temperature. We sweat as
our body temperature increases to cool our body off and lower body temperature.
How
much water do you need? Several
factors can affect how much water each individual needs to consume. Climate, physical activity demands, how much
you’ve sweated, overall body size, etc. are all factors that will affect your
personal water intake needs.
For example, during exercise our body
tells us when we are thirsty if we are sweating and our body temperature is up.
This is one of our mechanisms in the body to keep us from becoming extremely
dehydrated. This typical isn’t perceived
until 1-2% of our body weight is
lost. Not only has exercise performance already decreased, your mental
clarity and focus has already dropped (even if you not exercising).
To prevent this from happening, there
are two different ways we can determine our individual fluid requirements.
1.
Estimate Fluid Needs by Metabolic Rate – for every 100 kcal of metabolic rate, you ingest
80-110 mL of water. For example – BMR = 2,000 kcals, you require 1.6-2.2 liters
of water per day
2.
Estimating Fluid Needs by Body Weight – for every kilogram of body weight, you’d ingest
30-40 mL of water. For example – 50 kg (100 lb) individual requires 1.5-2
liters of water per day. *1 liter = 4 cups* When
you are not exercising, individuals’ average 2 liters (8 cups) water per day
**These
are minimum requirements. Based off of the other factors listed above, you may
need to consume a lot more water**
Here
are the consequences based off of total body water % loss –
0.5%
= increased strain on your heart
1%
= reduced aerobic endurance
3%
= reduced muscular endurance
4%
= reduced muscle strength, reduced motor skills, heat cramps
5%
= heat exhaustion, cramping, fatigue, reduced mental capacity
6%
= physical exhaustion, heat stroke, coma
10-20%
= DEATH.
There are hydration strategies that can
keep you hydrated and at your best performance. You macronutrients affect your
hydration. The higher are carbohydrate intake, the more water our body will
store, about 3-4 grams of water for every gram of carbohydrate. Carbohydrates
can improve rate of fluid absorption and enhance endurance, increase blood
glucose, decrease stress response of training, improve immune function,
decrease inflammatory damage after training, enhance whole body hydration, and
improve muscle and liver glycogen synthesis.
Several minerals can also increase water
storage and hydration. Electrolytes are minerals such as sodium, potassium,
chloride, calcium, and magnesium. Maintaining a proper electrolyte balance is
essential for normal physiological functioning. Normal dietary sodium intake
can replenish short exercise bouts, but longer duration exercise sessions
should consider using a replacement drink such as a carbohydrate drink with
electrolytes added to it. The concentration of this drink should be low to
avoid any GI distress and discomfort and keep from hindering absorption.
Recommendations
for before and after exercise –
1.
Pre-Hydrate –
consume 500 mL of fluid 30 minutes prior to exercise
2.
During – 250
mL every 15 minutes of exercise
3.
Post Hydrate –
Ingest 0.8 grams of carbs per kg body weight in approximately 500 mL – 1 L of
water
-For example – 50 kg body weight individual needs 40
grams of carbs in 400 mL of water (50 kg X 0.8 g)/0.1 mL – a ½-1 tsp of sodium
can be added to ensure adequate electrolyte replacement
4. Rapid
Rehydration – 1.5 L of fluid per hour
until body water and weight is replenished (maximal rate of fluid absorption in
the body)
5. Adding
Protein – can enhance muscle protein
synthesis, improve recovery, reduce muscle soreness, decrease protein breakdown,
enhance glycogen resynthesis, enhance immune function, and increase the use of
body fat during subsequent exercise
1 hour of
exercise = 30 g carb + 15 g protein in 600 mL water = 30 g carbs + 15 g protein
in 600 mL of water (I recommend whey protein powder and dextrose)
Remember that exercise intensity and duration both
determine hydration strategies! These strategies are designed for optimal
results in more extreme situations of fluid loss and exercise intensity. Normal
daily intake plus a little bit more is all that is needed if high sweat rates
and fluid loss aren’t apparent.
Water is essential for life. Bring a water bottle with
you and stay hydrated. Even try adding fruit to you water for extra flavor. Whatever
you do, drink up and keep your body happy and healthy.
Happy Hydrated Running J
