HYDRATION Flashcards
Body water is tightly controlled by
thirst and kidney regulation of urine output
daily variation of bodt mass is under _%
1%
Hyperhydration
higher body mass, less needing to pee, stay hydrated for longer
Hypohydration
not losing water but having a low water content
when you lose more sweat then the fluid you drink
Dehydration
the process of losing water/fluid
Water things lose and gain water
losses
- sweat
- urine
- respiratory
- faecal
gains
- metabolic water production (when muscles contract they produce some small water)
- food
drink
Does coffee dehydrate you
no, but the caffeine does, but the fluid from the whole coffee cancels out the caffeine dehydration
What are the 3 important times for hydration
pre - during - post exercise
Hydration during exercise - sustainability
the mess water stations can have etc
Measures of Pre-Exercise Hydration
gold standard - Serum Osmolarity, best euhydrated measure
- urine colour (most accessible)
- urine osmolarity
- urine specific gravity (most common, yes or no answer)
First Void Sample
first sample of pee when you wake up
Everyone ones hydration levels are …..
different
hypo hydrated and RPE of sessions
the more hypo hydrated you are the harder you will find the training sessions, but can be lots of variations with this
Pre-Exercise Guidelines
- start exercise in a euhydrated state
- drink 5-7ml/kg 4hr before the session, if urine still dark 3-5ml/kg 2 hr before - but is the practical for a 6 am training, no
- drink temp is important in the heat
Effects of Dehydration
- depends on the event
- decreases skill and mental performance
- opening of the blood brain barrier
- increased perception of effort
Do you want to be over or under hydrated for exercise
you don’t want either, you want a good balance
if you are use to being dehydrated for exercise this impacts their effects of exercise
Successful athletes have shown to have dehydration levels of
5-8%, you don’t often want to lose less than 2%, you often lose weight depending on your exercise intensity
If you gain weight during exercise this means your not …
dehydrated
Individual Variability with Hydration
you can’t change how much you sweat, but they can change their drinking behaviour
Athletes perception on fluid balance
people often lose alot more than they think they lose but they are also drinking more than they think they are but they think they are dehydrated
Perceived vs Actual Sweat Loss
traditionally hydration strategies have been based on the recognition of one’s sweat rates, but we underestimated our sweat rate by around 40-50%
OverHydration causes
- increase body mass
- urination
- dilution of blood sodium concentrations
- hyponatremia?
Hyponatremia
usual Na conc. is 135-145 mmol/L
- severe health consequences like fatigue
both this and hydration have similar symptoms, so this is problematic, so we weigh them to tell what one it is
Risk Factors for Hyporntermia
- exercise duration over 4hr
- slow speeds / slowing running
- females
- low body weight
- excessive fluid intakes
- extreme environments
Can sport drinks/electrolytes prevent hyponatremia
no
ACSM Drink Guidelines
- try to limit dehydration to 1-2% loss in body mass otherwise performance will be impaired
- may not be feasible in hot environments
- avoid gaining weight
so don’t loose more than 2% body mass, minimise dehydration in the heat and avoid gaining weight
How to measure the amount of sodium you lose
catch sweat to measure the sodium amount in the sweat
If you loose lots of sodium in sweat what should you do and why
increase the amount of sodium in the diet
why - because does not increase blood sodium but improves palatability, maintain ECV
What is the main electrolyte lost sweat is …..
sodium
Post Exercise Recovery Guidelines
the 3 R’s
rehydration, repair and restore
3 R’s
rehydration - restore electrolyte and fluid balance
repair - muscle repair and regeneration (protein)
restore - muscle and liver glycogen levels to those pre-exercise (carbs)
Recovery Guidelines - Post Exercise
- if the exercise is less than 24hr apart then it requires a more structured rehydration plan but smaller regular volumes work best. rehydration within 6 hr requires volumes greater than deficits
eg. drink more than we lose
During recovery why should we drink more than we lose
because we are still urinating
Drink Volume
dehydration - increase AVP - increase water re-absorption
Ingestion Rate of Water
a given volume over a longer period of time it likely to have more efficient rehydration, but this rate is still unclear
Macros and Intake
carbs - enhances how much fluid can be retained and maintains glycogen stores
protein - helps repair and grow muscles
= chocolate milk has high protein and carbs so so so good after exercise
