Week 10: water balance and hydration Flashcards
TBW is ____% of body mass
50-75%
blood plasma makes up ___% of TBW
7.5%
Interstitial fluid makes up ___% of TBW
30%
Intracellular fluid makes up ___% of TBW
62.5%
Water is tightly regulated by(2)?
- the nervous system
2. hormonal activity
The anti-diuretic hormone function?
Primarily effects (water) decreasing urine output
Aldosterone function?
Stimulates the absorption of sodium in kidney (sodium focused)
____ is the main electrolyte in extracellular fluid
sodium
Sodium accounts for ___% of plasma osmolarity
50%
The kidneys either conserve ___ or conserve _____
water, sodium
Thirst is evoked by elevated _____ osmolarity and (some) reductions in ___________…?
plasma, blood volume and pressure
Hyponatremia :
low plasma levels
Normal plasma sodium concentrations are _____mmol/L
140-144mmol/L
Symptoms of low sodium plasma concentration occurs at ____ mmol/L and less
130mmol/L and less
Sodium plasma levels below 120mmol/L can cause…
risk of seizures, coma and death increases
Symptoms of initial low sodium plasma levels can be…
Mental confusion, weakness, fainting, (all similar to dehydration -> can cause confusion and make it worse if they drink more water!!!)
Normal body temp:
36-38 degrees celcius
Normal body temp for exercise:
38-40 degrees celcius (any higher can be heat exhaustion or lead to heat stroke)
4 factors that effect the environmental stress?
- Ambient temp
- Relative humidity
- Wind velocity
- Solar radiation
If body temp rises, the hypothalamus ….. (2)
- increase blood foo to skin
- increases sweat rate
Conduction:
Transfer of heat through direct contact
Convection:
Transfer of heat through fluid or gas
Radiation:
Transfer of heat through electromagnetic waves
Evaporation:
Heat loss through water vaporisation from skin
Skin temp > environment temp =
heat lost from skin (through evaporation, convection and conduction)
environment temp > skin temp
Heat is gained (through conduction and convection)
If environment saturated with vapour, what happens to evaporation?
It does not occur, then body does not lose heat
1L of O2 consumed = ____ of heat produced
16 kj (4 cal)
What happens to the rest of the heat in the body? (2)
- Lost from overlying skin
- Passed to core core through venous BF to heart
Can you improve thermoregulatory response?
Yes, by training at high intensities (70-100% vo2 max) which should increase body temp above 39 degrees celcius
Adaptation of increase thermoregulatory response will result in…?
- earlier sweating onset
- increased total sweat amount
- Increased the sensitivity between core temp and sweat rate
- Hypertrophy of sweat glands (increased size not #)
Is there an adaptation to dehydration?
No
For every L of body fluid lost there is ……(3)
- Increase in HR by 8bpm
- decrease in CO by 1L/min
- increase in core temp by 0.3 C
If you are dehydrated, exercise will cause….(2)
- body temp to rise FASTER
- higher HR
What level of dehydration can performance be affected at???
1-2%
Thirst threshold begins at __% of fluid loss
1%
Stronger thirst, vague discomfort, decrease hunger begins at __% of fluid loss
2%
Dry mouth, decreased urine output begins at __% of fluid loss
3%
20-30% decreases in performance begins at __% of fluid loss
4%
Decreased concentration, headache, impatience, sleepiness begins at ___% of fluid loss
5%
Serious health conditions begins at ___% of fluid loss
6%
What is actually happen to make fluid loss decrease performance?
⬇ blood volume ⬇ skin blood flow ⬇ sweat rate ⬆core temp ⬆rate of muscle glycogen use
Hyperhydration goal is to…
maximise TBW content prior to competition
Downsides of hyperhydration….
- GI discomfort
- much of the water is excreted
- may not be practical
- not as beneficial as they thought
Strenuous exercise ___mins or less has NO advantage w/ fluid intake
30 mins or less
Exercise for ___hr or in ____ conditions should have water with electrolytes-CHO
1 hr, hot conditions
Why is it difficult to match fluid intake with fluid output? (4)
- GI discomfort
- Sweat rates vary
- Some sport rules may not allow or may not be practical
- Thirst is not a good indicator of requirements
Sweat rate is almost __x higher in hot environments
2x
Hypertonic =
increased solutes outside cell -> water moves out
Hypotonic =
increased solutes inside cell -> water moves into cell
Isotonic =
Same amount of solutes outside and inside cell, NET move zero (although they still move)
Ensure to avoid hypotonic/hypertonic solutions
Avoid hypertonic solutions !!!!
Typical fluid ingestion is ___L/hr
0.4-0.8L/hr
It is better to give more/less fluid than you know they lost…
MORE (125-150% of what was lost)
