Hydration

Question 1

Adult body water content

Answer 1

50-60% body mass
lean body tissue = ~75% water
fat mass = ~5-10%

Question 2

Functions water

Answer 2

temp regulation
nutrient transport (blood/plasma)
protection (tears to protect eyes)
biochemical reactions (end product metabolism/hydrolysis)
medium for reactions

Question 3

Euhydration

Answer 3

fluid water balance
fluid loss = fluid gain

Question 4

Dehydration

Answer 4

body water deficit greater than normal daily fluctuation
negative fluid water balance
due to inadequate fluid intake relative to fluid losses (sweat)

Question 5

Net body water balance

Answer 5

difference between fluid water gain (intake + production) and fluid loss
maintained on day to day basis
challenged during periods of high sweat rates

Question 6

During exercise sweat rates

Answer 6

environ - hot/humid = increase temp = sweat
muscle contract = create heat = sweat
lose water

Question 7

Assessment tools to determine hydration status

Answer 7

plasma osmolality
body mass change
urine specific gravity
urine density relative to water
euhydrated at 1.003-1.035

Question 8

> 2% acute body mass reduction

Answer 8

exercise-associated dehydration
90% chance body water deficits sufficient to be classed as dehydration

Question 9

Osmolality

Answer 9

measure of the total dissolved particle conc
ions
275-295 mOsm/kg

Question 10

Why do we sweat?

Answer 10

body’s principal means of preventing excessive body temp during exercise

heat production during exercise
L O2 = 4kcal heat produced
pass to body core
hypothalamus sense increase in body temp
increase blood flow to skin = initiate sweat response

Question 11

Evaporative cooling

Answer 11

1L sweat evaportated = remove 573kcal heat from body

Question 12

Sweat

Answer 12

water loss from water component of blood (plasma) = reduced plasma and blood volume
sweat hypotonic = plasma osmolality reduces

lower blood volume = increase vascular strain due to heart working harder

Question 13

Mechanism control body temp

Answer 13

sweating
evaporative heat loss

Question 14

Dehydration on aerobic performance

Answer 14

29 degree celcius threshold
increase temp (1 degree) = performance decrease (1.6%)
blinded dehydration impair endurance performance

Question 15

Mechanisms of impaired aerobic performance in warm-hot conditions

Answer 15

Cardiovascular – blood pressure and blood flow, oxygen delivery, metabolite removal

Central nervous system – brain metabolism, brain temperature

Peripheral muscular factors – temperature, metabolic, afferent feedback

Psychological – thermal comfort, perceived exertion

Respiration – breathing sensations

Question 16

Pre exercise

Answer 16

2-4h = 5-10ml fluid/kg body weight
more fluid if no/dark urine
fluid retention add sodium/salt

Question 17

During exercise

Answer 17

limit body mass change through loss of fluid to <2%
limit excessive electrolyte imbalance (risk of hyponatremia)
0.4-0.8 L/h
>2h - add sodium (salty sweaters)
>1h - add CHO

Question 18

Post-exercise

Answer 18

rapid recovery (<12h) = 1.25-1.5L kg/BM loss
+ sodium
more recovery time: resume dietary practices + extra plain water

restoration of sodium and fluid balance

Question 19

Sweat rate calculation

Answer 19

L/h

weight before - after = weight loss
bottle weight before - after = volume consumed

weight loss + volume consumed - urine loss / duration of exercise (h)

Question 20

Sodium during exercise

Answer 20

critical for electrolyte balance for functions in body

Question 21

CHO-E solution

Answer 21

supply CHO as major energy source
effective in maintain hydration status

80-350 kcal/L
sodium = 20-50 mmol/L

Question 22

Hyponatremia

Answer 22

low blood sodium (<135 mmol/L)
arise from over drinking fluids more than fluid lossses (high sweat sodium losses + low sodium beverages)
recreational athletes/women at risk
dangerous, immediate medical attention

Question 23

Hyponatremia sytmptoms

Answer 23

changes in personality (confusion or short temper)
fatigue
convulsions or seizures
feeling weak
loss or consciousness/coma
low BP
nauseous/vomiting

Question 24

Sodium post exercise

Answer 24

dilute conc = consume 50% not reach normal level
ongoing urine release = net balance remain neg

high conc = 125% (reach break even levels)
closer to body water balance in short time
more sodium helps with retention/reabsorption in kidney