Hydration

Water and fluid balance – Recommendations for fluid intake

The quantity of water needed to ensure optimum health is often quoted around eight glasses of water that equates to about 2 -2.5 litres of water a day or approximately 1 litre for every 1000 calories expended on a daily basis. This is a general guideline, and hence, the consumption of water may need to be elevated to counteract sweating which results from exercise and the dehydrating effect of many substances like caffeine, alcohol, an air conditioned environment, and possible medical conditions. Fluid intake should be continuous throughout the day and can be taken in many ways, not only through the liquids taken on board, for many people the majority of fluid they consume each day The effects of dehydration (loss of fluid as % of body weight):

• 1% loss: Generates thirst sensation
• 2-3% loss: impaired performance and increased body temperature
• 4% loss: 20-30% decrease in endurance performance shown in some studies
• 5-6% loss: Heat exhaustion: heat cramps, chills, nausea, clammy skin, rapid pulse, dehydration from this point onwards can be fatal, children and older people are more at risk

Before exercise:

• Drink 16 ounces (450ml, about half a litre) up to two hours before. Kidneys need 60-90 minutes to process excess liquid, so this will be excreted before the event/activity. Too much fluid taken immediately before an activity may cause ‘sloshing’ in the stomach
• Drink 4-8 ounces (110-225ml), 5-10mins before activity. This will be available to replace sweat losses, from the onset of exercise

During exercise:

• Water can travel from stomach to skin in 9-18 minutes after drinking. Hydrate early from the start of exercise
• Ideally drink every 10-15 minutes during activity

After exercise:

• Continue to drink
• Salt loss (sodium) is not usually severe and additional salt does not need to be replenished
• All varieties of drinks are suitable for re-hydrating, although hypertonic drinks will be very slow compared to water, isotonic or hypotonic fluids. Dependent on personal tastes, availability. Preferably choose decaffeinated products