thermal stress and hydration Flashcards
ICF
fluid found inside of cells
electrolytes found in ICF
primarily K and some NA
- ex: muscle cells and red blood cells
ECF
fluid found outside cells
electrolytes found in ECF
primarily NA and CL- and some K
ex: blood plasma (interstitial fluid), and sweat gland
Total body water
amount of water in the various fluid compartments
the proportion of BW and water goes ___ with excess body fat
down
total body water equation
0.60 x weight in Kg =
body fat has ___ % of its water weight
10%
dehydration
condition caused by the loss of too much body water
severity of body weight 1.2%
starts to compromise physiological function and influence performance
severity of dehydration >3%
performance decrement is present
-increased risk for heat illness
-heat cramps
-heat exhaustion
severity of dehydration >5%
health is now compromised
-increased risk for heatstroke
fluid balance
water in: fluids, food, metabolic water
water out: pee, poop, breathing, sweat loss that we dont realize is happening
negative fluid balance
water in < water out
causes for negative fluid balance
diuretics, sickness, low fluid intake, excessive sweating without replacement
symptoms of dehyradation
fatigue
thirst
less frequent urination or darker urine
headache
dry mouth
dry skin
rapid heart rate
hypothermia
when body temperature is below 95 F
headwind
you add
tail wind
you subtract
hyperthermia
when core temperature is too high (above 100)
what temperature does protein start to denature at
104 F
green flag for exercising in the heat
below 65 F
yellow flag for exercising in the heat
between 65-73
high risk for exercising in the heat
between 73-82 F
heat illness
complications brought on by the core temperature and electrolyte imbalances which can cause disabling complications collectively termed “heat illness:
heat cramps
severe, involuntary and sustained muscle spasms usually in the active muscles used
what causes heat cramps
imbalances in fluid electrolytes
heat exhaustion
general feeling of fatigue accompanied by a weak rapid pulse, low blood pressure, headache, dizziness, and vomiting
tachycardia and hypotension are causes by
pooling of blood in peripheral vessels which are dilated for thermoregulation
hypovolemia
when blood volume is low
hypervolemia
when blood volume is high
heat stroke
most serious of heat-related conditions and medical attention is needed
-excessively high core temp
-absence of sweating
treatment for heat stroke
immediate fluid and electrolyte replacement and bath
fluid imbalance in exercise
- beginning exercise in a dehydrated state
- poor fluid replacement
- dehydration
thermoregulation: hypothermia
- hypothalamus senses blood temperature when its too cool and it activates
- causes vasoconstriction in the peripheral extremities and shivering
- vasoconstriction causes less heat loss to the enviroment
- shivering raises body temp
thermoregulation: hyperthermia
- The hypothalamus senses warmblood
- causes vasodilation in peripheral and near skin and activates the sweat glands
- sweating should make the temp go down
what causes vasodilation and constriction
neural stimulation
dehydration causes
hypovolemia
Describe the impact humidity would have on thermoregulation of hyperthermia
Effects the ability of sweat to evaporate into the air
Describe the impact HOT air temperatures would have on thermoregulation of hyperthermia.
Decrease the ability to thermoregulate because it compromises convection and radiation
sweating: to solve hyperthermia
- stimulus: hot blood
- neural control center - hypothalamus - brain
- SNS stimulates: sweat glands and vasodilation
sweat
fluid released by sweat glands onto the skin of some mammals
evaporation of fluid off skin =
convection and radiation
minerals in sweat
NA and CL-
blood plasma lost from sweating decreases
blood volume
central circulation
organs and arteries
peripheral circulation
superficial vessels
larger vessel volume
= more blood in them
if there is more blood in the peripheral circulation then
less blood in central circulation
hypotension
low blood pressure
Cardiac output equation
CO= SV and HR
SV
volume of blood pumped with each ventricular contraction
preload
end-diastolic volume
diastole
relaxation of the heart
SV is dependent on
left ventricle preload
preload is dependent on
blood volume
preload is lower due to
pooling in periphery (blood volume is lower centrally)
or sweating
if SV is lower then HR needs to ______ to maintain CO
increase
what causes of absence of sweating
hypothalamus will remove sweating stimulus if blood volume gets too low or becomes hypertonic
hypovolemia is associated with
hypotension
tachycardia
and absence of sweating
sweat rate
dont want to lose 1-2%
1 L of H20 =
1 kg
NA AI
1500
NA UL
2300
calculating sweat rate
- weight loss during training - weight before and after
- volume consumed - water bottle weight before and after
- urine loss
- duration of excerise
what you need to measure sweat rate
conditions similar to competiton
bw scale
kitchen scale
bottles of water
towels
calculator
factors that determine your sweat rate
- acclimation and training status
- body fat %
- clothing
- windspeed, temp, humidity
- intensity of exercise
- genetics
how many days to get acclimated to the heat
5-7 days
acclimation to heat: plasma volume
increases and allows you to sweat more
acclimation to heat: core and skin temp
decreases a little bit - to allow for flexibility as temperature increases
acclimation to heat: Hr
decreases
acclimation to heat: exercise capacity
increases
plasma volume increase =
preload increase
preload increase =
SV increase
increase SV =
decrease in HR
training adaption status
onset of sweating - sooner
sweat more - evaporation of sweat is primary way of thermoregulating
sweat is more dilute = less NA loss
monitoring hydration method
WUT
weight
urine
thirst
weight in WUT method
compare to reference weight after going pee and poop
urine in WUT method
color - lighter = hydrated
darker = less hydrated
volume - less volume = less hydrated
more volume = more hydrated
thirst in WUT method
presence of
and abscence
symptoms in WUT method
headache or other symptoms of dehydration
homeostatic perturbation
- excessive sweat loss
- blood becomes hypertonic
- hypothalamus and stimulates pituitary gland
- pituitary gland releases ADH
- adh - antidiuretic hormone
- kidneys
nutritional approach to hydration
replace h20 and electrolytes
potassium AI
4,700
NA in diet
3/4 from processed foods and restaurant foods and prepackaged food
-not in natural form of food
K in our diet
primary - fruits and veggies
secondary - meats and beans
