Water Requirements and Fluid Balance

1
Water Requirements and Fluid Balance

• Chapter 8

2
Major Functions of Water

• Provides essential building material for cell
  protoplasm
• Protects key body tissues (spinal cord, brain)
• Maintains normal osmotic pressures
• Main constituent of blood
• Regulation of body temperature
• Important in hearing, vision, taste

3
(No Transcript)
4
Definitions

• Euhydration normal body water content
• Hypohydration body water deficit
• Dehydration the dynamic loss of body water or
  the transition from euhydration to hypohydration

5
(No Transcript)
6
Daily Water Loss

• Urine 1,300 ml
• Water in feces 100 ml
• Exhaled air 200 ml
• Skin (insensible perspiration) 600 ml
• Sweat 2-3 L/hr
• TOTAL 2 - ??? liters

7
Daily Water Intake

• Approximate requirement 1 ml/kcal
• Food 700 ml
• Metabolism 300 ml
• Fluids everything else
• Non-diuretic fluids
• Diuretic fluids

8
Heat Production

• For every 1 liter O2 consumed
• 4 kcal of heat dissipated
• 1 kcal of heat used to perform mechanical work,
  ie. contraction
• 1000 watt power output would increase core temp
  by 1 C every 4 minutes
• Body can only tolerate a rise of 2-2.5 C before
  central fatigue occurs
• Above 40 C, heat exhaustion stroke

9
(No Transcript)
10
Why Dehydration Impairs Performance

• Reduced blood volume
• Decreased skin blood flow
• Decreased sweat rate
• Decreased heat dissipation
• Increased core temp
• Increase in muscle glycogen use

11
(No Transcript)
12
Effects of Dehydration on Performance

• At 2 of body weight loss, aerobic performance
  declines 5-10.
• At 5 of body weight loss, aerobic performance
  can decline up to 30.
• At 2.5 of body weight loss, high intensity
  effort lasting several minutes can be impaired by
  45.

13
Fluid Replacement Recommedations

• 12-16 oz of fluid 1 hour before exercise
• 12-16 oz of fluid 30 min before exercise
• 6-8 oz every 15 minutes during exercise
• Normal mouthful is 1 oz
• 24 oz per pound lost after exercise (150 of
  weight loss)

14
What to Drink?

• Carbohydrate, electrolyte beverage is best
  immediately before and during exercise
• 6-8 CHO (glucose polymer/fructose)
• 50-100 mg Na per 8 oz
• Increase palatability
• Maintain thirst
• Prevent hyponatremia
• Increase water absorption
• Decrease urine production
• Water is OK for normal re-hydration throughout
  the day

15
Heat Acclimatization

• Must exercise at gt70 VO2max
• Significant changes occur in 7-10 days
• Benefits
• Earlier onset of sweating
• Sweat more
• Larger sweat glands
• Increase in total blood volume

16
(No Transcript)
17
(No Transcript)
18
(No Transcript)