Hydration

Question 1

Functions of water?

Answer 1

Nutrient transport
Protection
Temperature regulation
Biochemical reactions
Medium for reactions

Question 2

Total body water for humans?

Answer 2

50-60% of body mass index

Question 3

What is net body water balance?

Answer 3

• The difference between fluid water gain and fluid loss

Question 4

What is another name for dehydration?

Answer 4

Hypohydration

Question 5

How do you know if you are dehydrated?

Answer 5

• Brown during urination
• > 2% body mass reduction = 90% chance of dehydration

Question 6

Types of dehydration assessments?

Answer 6

• Osmolality- a measure of the total dissolved particle concentration
• Typically 275-295 mOsm/kg
• Dynamic dehydration assessment can be tracked well with
• Body mass changes
• Plasma osmolality
• Urine specific gravity

Question 7

What happens when we sweat?

Answer 7

• Heat production during exercise
  
  • For every L of oxygen consumed 4kcal of heat is produced and only about 1kcal is used to perform mechanical work
  • Most of the heat is passed to the body core
  • Hypothalamus senses increase in temperature
  • Responds to increase blood flow to skin and initiate sweating response

Question 8

What is hyperthermia?

Answer 8

Excessive rises in body temperature during exercise

Question 9

What is normal body temp and body temp during exercise?

Answer 9

• Normal body temperature is 36-38 degrees
• During exercise is 38-40 degrees

Question 10

How many calories will 1litre of sweat evaporated remove from the body?

Answer 10

573kcal

Question 11

What are the potential mechanisms of impaired aerobic performance?

Answer 11

Cardiovascular - blood pressure and blood flow, oxygen delivery

Central nervous system - brain metabolism, brain temperature

Peripheral muscular factors - temperature, metabolic, afferent feedback

Psychological - Thermal comfort, perceived exertion

Respiration - Breathing sensations

Question 12

What are the ACSM guidelines for 2-4hr pre event hydration?

Answer 12

• 5-10ml fluid/kg body weight
• More fluid if dark urine

Question 13

What are the ACSM guidelines for hydration during exercise?

Answer 13

• Sufficient fluid to limit body mass losses to <2% and limit excessive electrolyte imbalance
• > 2h - add sodium
• > 1h - may consider CHO addition

Question 14

What are the ACSM guidelines for hydration post-exercise?

Answer 14

Rapid recovery: Consume 1.25-1.5L for each kg BM loss + sodium

More recovery time: resume dietary practices + extra plain water

Question 15

Why is sodium important during pre exercise, during exercise and post exercise?

Answer 15

Pre exercise: Fluid retention

During exercise: Limit electrolyte losses (risk of hyponatremia), stimulate thirst

Post exercise: Restoration of sodium and fluid balance

Question 16

How do we characterise a carbohydrate (CHO-E) solution?

Answer 16

• It should supply carbohydrates as the major energy source
• Be effective in maintaining hydration status
• Energy: 80-350kcal/L from carbohydrates, >75% of energy from carbohydrates with high glycaemic response
• Sodium: 20-50mmol/L (460-1150mg/L)

Question 17

What is the sodium content of Fit water vs Lucozade sport?

Answer 17

Fit water = 21mg/100ml
Lucozade sport = 50mg/100ml

Question 18

What is hyponatremia?

Answer 18

• Low blood sodium (<135mmol/L)
• Can arise from over drinking fluids with low sodium more than fluid losses
• Recreational athletes and women at greater risk
• Dangerous, immediate, and accurate medical attention

Question 19

What is the formula for sweat rate?

Answer 19

Change in body mass + fluid intake / number of hours of exercise

Question 20

What should athletes try and minimise their percentage body mass losses to?

Answer 20

No more than 2% body mass loss