Lecture 5 - Hydration Flashcards
what is euhydration
normal state of body water
what is hyperhydration
a sustained increased state in body water
what is hypohydration
a sustained decreased state in body water
what is dehydration
the process of losing body water, rather than a state of low body water
how does the body gain water
metabolic water production
food
drink
how does the body lose water
faecal
respiratory
urine
sweat
what are the negatives to measuring pre exercise hydration with urine osmolarity
- accuracy needs first void sample
- expensive
what are the negatives to measuring pre exercise hydration with urine specific gravity
accuracy needs first void sample
what are the positives to measuring pre exercise hydration with urine specific gravity
relatively cheap and quick results
what are the positives to measuring pre exercise hydration with urine colour
very cheap and quick results
good education tool
what are the negaitves to measuring pre exercise hydration with urine colour
accuracy needs first void sample
affected by other dietary components
what is the negaitve to measuring pre exercise hydration with serum osmolarity
expensive
what is the positive to measuring pre exercise hydration with serum osmolarity
accuracy gold standard
what are the guidelines to hydration in exercise
begin exercise euhydrated
slowly drink 5-7 ml/kg at least 4 hours prior to exercise
if urine still dark drink further 3-5 ml/kg 2 hours prior
what does dehydration cause a decrease in
decrease in skill and mental performance
what does dehydration open
opening of the blood brain barrier
what does dehydration increase
increased perception of effort
what is the equation to measure sweat loss used in practice
sweat loss (L) = Body mass loss (kg) + fluid intake (L) - urine produced (L)
what is the equation to measure dehydration used in practice
dehydration = (body mass loss / initial body mass) *100
in terms of hydration during training, do players know what they are doing
not really
what are the possible effects of over hydration
- increase in body mass
- urination
- dilution of blood sodium
- possibly hyponatremia
what is hyponatremia linked to
serum sodium concentration
what are the symptoms related to hyponatremia
- fatigue
- lethargy
- brain aneurisms
- possible death
what are the risk factors to hyponatremia
- exercise duration >4h
- slow speeds
- females
- low body weight
- excessive fluid intakes
- non steroidal anti inflammatories
- extreme environments
the addition of sodium to drinks ingested during exercise cannot …..
cannot prevent the development of exercise associated hypoantraemia in athletes who drink to excess
what are the ACSM drink guidelines
- try to limit dehydration to <1-2% loss in body mass
- in hot environments this may not be feasible, in this case try to minimise dehydration
- avoid gaining weight
excessive water intakes are more common in what athletes
recreational athletes
what electrolyte lost in sweat is
sodium
how to calculate salt losses
sweat sodium concentrations (mmol/L) * sweat loss (L/h)
sodium improves palatability, what does this increase
increasing palatability could increase fluid intake thereby delaying the onset of dehydration
fluid intakes are greatest with what concentration of sodium
30 mmol/L NaCl solution
sports drinks are usually what sodium concentration, anything above this people usually wont drink them
20-40 mmol/L
exercise less than 24 hours apart requires a more …
structured rehydration plan
what type of volumes are best for rehydrating after exercise
smaller regular volumes
what are the three R aims of recovery
- restore
- rehydrate
- repair
what is meant by restore in recovery aim
muscle and liver glycogen levels to pre exercise
what is meant by rehydrate in recovery aim
restore fluid and electrolyte balance
what is meant by repair in recovery aim
muscle repair and regeneration
study found what happens if you just replace body weight lost in rehydration post exercise
you wont get back up to euhydrated
how many times body mass losses is required to become euhydrated post exercise
1.5 time body mass losses
sodium is the major ion of the what fluid
extracellular fluid
The addition of carbohydrate to rehydration drinks enhances fluid retention if the concentration of carbohydrate is …. and volume of fluid is ….. ingested are sufficiently high
(6-10%) …. (150% BM loss)
what are best when used together not in isolation to support recovery
protein, carbohydrates and water
why include sodium ? ?
- improves palatability
- maintains extracellular volume
- may attenuate the decline in blood sodium
what are the ACSM carbohydrate guidelines
a carbohydrate intake of 1.5 g/kg during the first 30 min and again every 2 hours for 4 to 6 hours will be adequate to replace glycogen stores
what are the ACSM rehydration guidelines
1.5 times body mass loss
what are the ACSM protein recommendations
0.25-0.3 g/kg
what is euhydrated in urine osmolarity measure
<700 mOsmol/kg
what is euhydrated in urine specific gravity measure
<1.020 mg/cm3
what is euhydrated in urine colour
<3 on the scale
what is euhydrated in serum osmolarity measure
~285 mOsmol/kg
when is beverage temperature important
when exercising in the heat
exercise induced hypohydration leads to (what is the overall effect of this)
decreased plasma volume
increased plasma osmolarity
increased thirst
decreased mood
these have secondary impacts that leads to impaired endurance performance
even without fluid ingestion how much plasma volume is restored and when
half of the loss in plasma volume is restored within 1 hour
how can total estimated sweat loss be calculated
(pre exercise weight - post exercise weight) + fluid consumed during exercise - urine produced
how to work out estimated sweat rate
total estimated sweat loss / exercise duration
how to work out level of dehydration (%)
weight change / pre exercise weight x 100
weight change (pre exercise body mass - (post exercise body mass + urine)) x 100 / pre exercise weight
what is the normal variation in body water
≤ 1% of body mass
what is it reported of % lost of starting weight in marathon
9.8% starting weight lost
what is one of the highest every sweat rates recorded
3.6L/hr
what are the sweat potassium concentrations
~2-8 mmol/L
what is the sweat sodium concentrations
20-80 mmol/L
