We are all regularly told to drink 2ℓ water or fluid per day, this helps to maintain hydration and flush through any toxins or waste products we have in our system.
Fluid losses do not only occur through
waste products such as urine; sweating and exhaling also expel body fluids.
Fluid losses are greatly increased in higher temperatures, humidity and during
prolonged exercise. Fluid loss tends to go hand in hand with loss of
electrolytes such as sodium and potassium. These losses result in a decreased
metabolism, increase in body temperature and an increase in heart rate. In turn,
all of these changes in body conditions result in an onset of fatigue and
therefore an overall decrease in performance.
Over the course of a 90 minute football game, for example, a player can easily loose up to 4% of their body weight through sweating. This equates to a large amount, when just 2% body water of a 70kg person is equal to 1.4ℓ. Therefore, fluid and electrolytes need to be replaced during exercise and topped up prior to exercise to combat these losses.
Sports drinks are ideal to have before, during and after exercise as they not only contain the vital fluids needed but also have carbohydrate for additional energy and electrolytes. These drinks are specially formulated for exercise, to help prevent dehydration if consumed at the correct times.
Sports drinks, however can be expensive. It is possible to make your own:
200ml squash (non sugar free)
800ml water
pinch of salt
or
500ml fruit juice
500ml water
pinch of salt
or
60g glucose powder
sugar free squash to taste
water to make up to 1ℓ
pinch of salt
Feeling
thirsty is too late and the negative effects of
dehydration have often begun to set in. It is important to regularly drink
around exercise and also throughout the day. This is the best way to keep
hydrated. Maintaining a healthy fluid balance does not only help with exercise
but also with: kidney function, cell hydration and healthy skin.
The "Pee Test" is a simple guide to see if you are sufficiently hydrated.
For sufficient hydration, aim for one of the top three colours, lower than this would indicate insufficient hydration, with possible negative effects. Short term urine colour does not accurately show hydration status for the body, long term however it can indicate whether an individual is sufficiently hydrated.
Armstrong et al 1994 Urinary Indices of Hydration Status
There are three categories of drinks;
hypotonic, isotonic and hypertonic. The main difference between the three is the
number of particles they have and thus how quickly they can be absorbed into the
body.
Hypotonic Drinks
Have fewer particles than that of the blood and are therefore rapidly
absorbed, for example, water. Water and weak squashes will replenish fluid
stores but will not replace used stores of carbohydrate or electrolytes. Some
ready made drinks, such as Lucozade Hydro Active, do contain electrolytes and a
small amount of carbohydrate as they are specially formulated.
Drinking water alone will decrease sweat production and increase urine
production, which is not desirable during exercise. Water will also dilute the
electrolytes already in the body and is therefore not the best drink to have
during exercise.
Isotonic Drinks
Have the same amount of particles as the blood and are often known as sports
drinks. They are rapidly absorbed, like hypotonic drinks whilst isotonic drinks
will also replenish used up carbohydrate. These drinks provide rapid
re-hydration, replenish fuel and fluid stores. Sports drinks also replenish
electrolyte stores, which means that they are ideal after exercise. Examples of
isotonic drinks are Lucozade Sport, Powerade and Gatorade, as well as the
recipes listed above for sports drinks.
Hypertonic Drinks
Have more particles than that of the blood and therefore take longer to
absorb. They take water out of normal circulation to dilute the extra particles,
this can therefore increase dehydration. Examples of hypertonic drinks are
Coke, fizzy drinks, Lucozade Energy. It is not advisable to use hypertonic
drinks before, during or after exercise.