Nutrition and Hydration Guidelines for Excellence in Sports - ILSI India

Guidelines for Excellence in Sports Performance
VI
Fluid Balance for Optimum Sports Performance
6.1 Water is critical for the proper functioning
of “body”. Hence, it is important that the loss of
water through sweat and urine is made up from
adequate consumption of water and other fluids.
6.2 Water is required for a variety of reasons:
• It transports nutrients and gases to
cells, wastes from cells, as also other
substances
• It combines with viscous molecules to
form lubricating fluids for joints, for
smooth movement of food through
digestive tract, etc.
• It helps maintain body temperature
• It maintains cellular shape, is an
integral part of cell membrane, cushions
organs and helps maintain body
structures
6.3 The total body water varies with age, sex,
body composition, etc. Water is about 70-75 per cent
of body weight is an individual with normal body weight.
6.4 Body water is made up of two parts, viz,
water inside the cell or intracellular and water outside
the cell or extracellular. The former contains high
percentage of sodium and chloride and the latter a
high percentage of potassium.
6.5 Maintaining normal blood osmolarity is
vital. The body mechanism is designed to ensure fluid
balance up to a point. For instance, a small rise in
blood osmolarity causes thirst. Similarly, the pituitary
gland sends out messages which cause the kidneys to
minimize urine volume.
6.6 During exercise 80% of the energy
metabolized in a hot environment is liberated as heat
in active muscles. The heat is transferred from warm
muscle tissue to the blood, and is then transferred to
the skin, where it is dissipated to the environment.
The body increases the dissipation of heat to the
environment by redirecting cardiac output, regulating
skin blood flow and altering the rate of sweat
secretion. If this heat is not removed from the body’s
core, it may result in a potentially dangerous increase
of internal temperature.
6.7 Thirst alone is not a good indicator of the
need for fluids. Research demonstrates that exercise
in hot adverse conditions can cause dehydration in
as little as 15 minutes. Drinking when in a
dehydrated state can cause gastrointestinal distress.
Athletes who say they cannot drink during a
workout because it gives them a stomach ache may
be allowing themselves to become dehydrated before
they take their first drink.
6.8 The time required for fluid to move from
the mouth to the sweat glands not only includes
uptake at the intestine, but also includes the rate at
which fluid empties from the stomach. Factors that
increase stomach emptying include: carbohydrate
content (optimal 6 to 10%), upright (versus seated)
posture, low (versus high) exercise intensity and mild
(versus hot) environmental temperature A small
concentration of carbohydrate will encourage rapid
absorption, but too much carbohydrate will slow
gastric emptying and can result in distress.
Consequences of Dehydration
6.9 Depending upon its degree dehydration can
result in ‘heat cramps’, ‘heat exhaustion’ and ‘heat
stroke’. Heat cramps begin as feeble twitchings and
progress to localized contractions of skeletal muscles
of the legs, arms, or abdomen. They occur in one
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