Hydration

Question 1

What is euhydration?

Answer 1

• A normal state of body water
• Deviations from this norm result in compensatory responses

Question 2

What is hyperhydration?

Answer 2

A sustained increase in body water (although often transient). You can extend hyper hydration with glycerol or salt.

Question 3

What is hypohydration?

Answer 3

A sustained decrease in body water ie. sweat more than you drink

Question 4

What is dehydration?

Answer 4

• The process of losing water
• Not a state of low body water

Question 5

How is body water controlled?

Answer 5

Tightly controlled through thirst and the kidney regulation of urine

Question 6

What is the daily variation of body mass?

Answer 6

less or equal to 1%

Question 7

What are the things that affect the loss of water balance?

Answer 7

• Sweat
• Urine
• Respiratory
• Faecal

Question 8

What are the things that affect the gain of water balance?

Answer 8

• Metabolic water production (contracting muscles produces water)
• Food
• Drink

Question 9

What are the important time points for hydration?

Answer 9

• Pre exercise
• During exercise
• Post exercise

Question 10

What are the measures of pre exercise hydration?

Answer 10

• Urine osmolality
• Serum osmolality
• Urine specific gravity
• Urine colour

Question 11

What is urine osmolality?

Answer 11

• Euhydrated <700 mOsmol/kg
• Accuracy needs first void sample
• Expensive

Question 12

What is serum osmolality?

Answer 12

• Euhydrated ~285 mOsmol/kg
• Accuracy gold standard
• Expensive

Question 13

What is urine specific gravity?

Answer 13

• Euhydrated <1.020 mg/cm^3
• Relatively cheap and quick results
• Accuracy needs first void sample

Question 14

What is urine colour chart?

Answer 14

• Euhydrated <3 on scale
• Very cheap and quick results
• Good education tool
• Accuracy needs first void sample
• Affected by other dietary components

Question 15

What does research on hydration status tell us?

Answer 15

Realise that there is huge variation in hydration status so there is never a on size fits all approach

Question 16

Are there effects of starting hypohydrated?

Answer 16

Some association with being hypo hydrated and finding the training harder (huge variation though)

Question 17

What are the pre-exercise guidelines?

Answer 17

• Start exercise in a euhydrated state
• Slowly drink 5-7ml/kg at least 4h before exercise
• If urine still dark, drink a further 3-5ml/kg 2h before exercise
• Think about urination - drink composition?
• Sodium helps with fluid retention
• Drink temperature is important in the heat

Question 18

What are the effects of dehydration?

Answer 18

• Depends on the event
• Decrease in skill performance
• Decrease in mental performance
• Opening of the blood brain barrier (effects your cognitive performance)
• Increased perception of effort

Question 19

What dehydration levels have successful athletes shown to have?

Answer 19

5-8%

Question 20

How to measure sweat loss?

Answer 20

• Sweat loss = Body mass + fluid intake
• Sweat loss (l/h) = (Body mass + fluid intake x 60) / time (mins)

Question 21

How to measure dehydration?

Answer 21

Dehydration = (body mass loss / initial body mass ) x 100
Note: if you can weight you are not dehydrated

Question 22

What are athletes perception of fluid balance?

Answer 22

• They are losing a lot more water than they think they are
• Athletes and adults engaging in exercise underestimate sweat losses by around 40-50%

Question 23

What is overhydration?

Answer 23

• Increase in body mass
• Urination
• Dilution of blood sodium concentrations
• Hyponatremia?

Question 24

What is hyponatremia?

Answer 24

• Usual serum Na concentration is 135-145 mmol/L
• Severe health consequences
• Symptoms include: fatigue, lethargy, brain aneurisms and death
• Incident in endurance events 10-40%

Question 25

What are the risk factors of hyponatremia?

Answer 25

- Exercise duration >4h - Slow speeds - Females - Low body weight - Excessive fluid intakes - Non-steroidal anti-inflammatories - Extreme environments

Question 26

What are the ACSM drink guidelines?

Answer 26

- Try to limit dehydration to <1-2% loss in body mass - In hot environments this may not be feasible, in this case try to minimize dehydration - Avoid gaining weight

Question 27

What is the reported loss of starting weight in a marathon?

Answer 27

9.8%

Question 28

What is the main electrolyte lost in sweat?

Answer 28

Sodium: 20-80mmol/L

Question 29

How do you calculate salt losses?

Answer 29

Sodium loss = sweat concentration x sweat loss

Question 30

Why include sodium in the diet?

Answer 30

- Improve palatability - Maintain extracellular volume - Might attenuate the decline in blood sodium

Question 31

Why is palatability important?

Answer 31

- Increasing palatability could increase fluid intake thereby delaying onset of dehydration - But large amounts of salt decrease palatability - Fluid intakes are greatest with 30mmol/L NaCl concentration

Question 32

What did the study of saltiness and exercise find?

Answer 32

- That when you are exercising, the preference of saltiness increases

Question 33

How does sodium ingestion promote fluid intake?

Answer 33

- Increasing thirst - Delaying dehydration

Question 34

How does sodium effect the body?

Answer 34

Sodium is important for intestinal absorption, however, the inclusion of sodium in a drink does not have a large effect on gastric emptying or intestinal absorption

Question 35

Are sports drinks or salt capsules better?

Answer 35

Sports drinks contain 20-40mmol/L. Salt capsules would negate the problem of taste but some actually contain less sodium than sports drinks

Question 36

What are the recovery guidelines?

Answer 36

- Rehydration: restore electrolyte and fluid balance. 1.5*body mass loss - Repair: muscle repair and regeneration. 20-30g protein - Restore: muscle and liver glycogen levels to those pre-exercise. ~1-1.2g/kg/h CHO during first 4-6hours

Question 37

Is larger or smaller volumes of fluid best?

Answer 37

Sipping retains more in the body than drinking a lot in one go. Smaller, regular volumes work best because otherwise you end up overloading your system

Question 38

What factors influence fluid balance?

Answer 38

- The volume you are drinking - How quickly you drink - The contents of the drink

Question 39

What does the addition of CHO to rehydration drinks do?

Answer 39

Enhances fluid retention if the concentration of CHO (6-10%) and volume of fluid (150%BM loss) ingested are sufficiently high