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  1. 1. ND Sport and Exercise Science Karen Vaughan Jones Sport Nutrition Hydration – Outcome 3
  2. 2. Fluid Balance and Hydration <ul><li>Water is one of the most important nutrients needed by the body </li></ul><ul><li>Water loss may be as high as a litre per hour during endurance-type exercise </li></ul><ul><li>This could be even higher if the exercise takes place in hot or humid conditions </li></ul>
  3. 3. Fluid Balance and Hydration <ul><li>The body needs to maintain a temperature within a narrow limit </li></ul><ul><li>During exercise temperature rises – extra heat is lost through sweating (evaporation of water from the skin’s surface </li></ul><ul><li>If this fluid loss is not replaced there is a danger of dehydration and performance may suffer </li></ul>
  4. 4. Dehydration <ul><li>Can affect performance by: </li></ul><ul><li>Reducing strength </li></ul><ul><li>Reducing power </li></ul><ul><li>Reducing aerobic capacity </li></ul><ul><li>Severe dehydration can cause heat stroke and has the potential of being fatal </li></ul>
  5. 5. Dehydration <ul><li>A loss as small as 2% of body mass can be enough to affect the ability to perform muscular work </li></ul><ul><li>For 75kg male this would be equivalent to fluid loss of only 1 ½ litres from the body </li></ul><ul><li>Important to minimise the risk of dehydration </li></ul><ul><li>Thirst is a very poor indicator of the body’s hydration status </li></ul>
  6. 6. Fluid Balance and Hydration <ul><li>To minimise the effects of fluid loss during training and competition sportspeople should: </li></ul><ul><li>Begin training/competition fully hydrated </li></ul><ul><li>Drink plenty both during and after the activity </li></ul>
  7. 7. Fluid Replacement Strategies <ul><li>Establishing a pattern of fluid intake should be an important part of training </li></ul><ul><li>Training should be used to practice fluid replacement strategies so they run smoothly in competitive situations </li></ul>
  8. 8. Fluid Replacement Strategies <ul><li>Fluid replacement can be quickened by: </li></ul><ul><li>Drinking still, cool drinks of a reasonable volume </li></ul><ul><li>Avoiding drinks that are too concentrated </li></ul>
  9. 9. Influences on Fluid replacement <ul><li>The more intense the activity the more the absorption of fluid is slowed </li></ul><ul><li>Unpleasant symptoms during exercise can be the result of leaving it too late to begin drinking – the body is already dehydrated </li></ul>
  10. 10. Checking fluid balance/replacement <ul><li>Weight and urine checks can provide an useful and simple way of monitoring fluid status during and after training </li></ul><ul><li>1kg weight loss during a training session = 1litre fluid loss </li></ul>
  11. 11. Checking fluid balance/replacement <ul><li>Visiting the toilet often to pass plenty of pale coloured urine is an indicator of good hydration </li></ul><ul><li>Small quantities of dark coloured urine indicates a poor level of hydration </li></ul><ul><li>These simple weight and urine checks before and after exercise can provide useful tools to assist in determining fluid requirements after training or during competition </li></ul>
  12. 12. Fluid Replacement Strategies for Exercise Based on body mass lost, replace losses by 150% 150-300ml Every 15-20mins Or 600-1200ml/hour 300-500ml 20-30mins before activity After During Before