Hydration for Health and Performance

How does water and hydration effect your health and improve performance?

Approximately 40-75% of the Body is Water

    • 2/3 of this Intracellular (Within Cells)
    • 1/3 Is Extracellular (Outside Cells)

The Amount of Water We Store Depends:

      • On Our Hydration Status
      • On Body Composition

The More Fat Mass You Have the Less Water You Store.


How Important is water?



  • Dehydration Occurs when Fluid Loss is Greater than Fluid Intake such that the Body Becomes Hypohydrated
  • Reduced Blood Volume
  • Dehydration Causes;
    • Reduced Blood Flow to Skin
    • Impaired Dissipation of Heat
    • Increased Body Temperature
    • Strain on Heart
    • Increase Exercise RPE

Dehydration and Performance

  • Exercising while dehydrate may increase RPE, reduce exercise capacity and reduce intensity and ultimately premature fatigue
  • Slight dehydration will not affect performance or physiology
  • 2% dehydration may affect performance
    • Sports involving decision-making will be affected most
  • There is a marked decrease in the ability to perform demanding muscular work at 4% dehydration
  • As dehydration progresses, blood becomes thicker due to reduce blood plasma volume and heart rate increases
  • Individual responses to dehydration are based on genetics and training status


To aid rehydration and maintain osmotic pressure, fluids containing electrolytes will assist in maintaining plasma volume.


  • Aid Absorption in the Intestine as Opposed to Replenish Losses
  • Water Movement Follows Sodium Movement
  • Sodium Increases Absorption of Water in Gut to Bloodstream
  • Presence of Sodium Promotes Urge to Drink
  • Sports Drinks are Isotonic

Isotonic Drinks

  • “Isotonic” drinks mean the fluid has the same osmolality as the body
  • Characteristics of Isotonic Drinks:
    • Same Osmolality as the Plasma
    • 4-9 g/100ml Carbohydrates
    • Faster Absorption from the Gut Vs Water
    • Quicker Rehydration Vs Water
    • Useful Energy Source

Drink Hydration Matrix

  • The beverage hydration index gives a comparison of the rehydration potential of various drinks
  • The drinks included in the study were compared to the rehydration potential of water
  • Contrary to popular belief beer, coffee and tea had similar rehydration potential to water

Hydration Guidelines

  • The duration of exercise and the amount of fluid loss will determine the type of solution to use
  • In general, water is a good rehydration solution as the sodium lost during exercise can be made up throughout the day through food/drink
  • The use of sports/carbohydrate replacement drinks will come down to:
    • Intensity/Duration of Exercise
    • Personal Preference
    • Post Exercise Hunger Levels
    • Food Choices After Exercise



  • The body must balance an increase in heat production during exercise with heat loss to maintain exercise intensity
  • Many intrinsic and extrinsic factors influence sweat rates
  • Duration, intensity of exercise and environmental factors influence sweat rates
  • Dehydration Likely Impairs Performance
  • Monitor Hydration Status
  • Always Start Exercise in a Hydrated State
  • Water + Normal meals & snacks may be sufficient to restore the body to rehydration
  • Sports +/- carbohydrate drinks are a useful tool for those exercising >90 minutes