Chapter 9- Water Flashcards
what is the body’s principal way of getting rid of excess heat ?
sweating
who has more %plasma in their body fluid- infants, men, or women?
adult men and women > infants
in general, describe the distribution of proteins, fat, and water in babies’ bodies vs adult bodies
in adults, the three are more equally proportioned, but in babies, most of the body is water
in most people, water accounts for what % of body mass
50-60
how much water by mass in lean body tissues vs fat ?
75% in muscle, etc
vs 5% in fat
who has more %interstitial fluid in their body fluid- infants, men, or women?
infants > men> women
who has more %intracellular fluid in their body fluid- infants, men, or women?
infants > men > women
why do men have more water content ?
they have more lean body mass and less fat than women
who has more %total fluid in their body infants, men, or women?
infants> men> women
who has more %fat- infants, men, or women?
women > men> infants
what are the two variables which determine the proportion of body fluids ?
age and gender
what are the 5 functions of water
resistance to temperature change cooling chemical reactions pH balance body fluids
what is the major avenue of water loss during rest ?
urination (60%)
what are the 4 avenues of water loss ?
urination 60% at rest
breathing
defecation
sweating
during exercise, how much % water loss is through sweat
up to 90%
what percent of energy is lost as heat ? what does this signify?
80%, meaning the body is not efficient at producing energy and using it
explain how 80% of energy is lost as heat
for every L O2, 1 cal energy is produced and 4 cal heat
calculate the energy made and the rate of heat production for an athlete consuming 4 LO2/min
4 LO2/min means that he is making it into 4x4=16 kcal/min heat and 4 kcal/min energy.
16 kcal/min heat= 960 kcal/L heat so this is the rate of heat production, which is 80% of the total energy production.
20% total energy would be 240 kcal/hr, and that means 240x 4.186 kJ/hr = 1004 kJ/hr
where does the heat go in the body?
small proportion to skin, most to body core with venous blood
during high intensity cycling, what happens to heat flow?
temperature increase in quads is 1 degree celsius / min which is a lot
when temperature in muscle is too high, what cools it down ?
has to be cooled down or else contractile proteins and enzymes will denature
thermoreceptors in hypothalamus increase sweating and blood flow to skin
during exercise at a constant work rate, how does heat production increase ?
in a square wave (step) fashion.
when does the rise in body temperature plateau ?
when heat loss from body = heat production
what causes the increase in core temperature in exercise ? (3)
exercise intensity
humidity
ambient temperature
what is the effect of a warm up on body temperature ?
intense warmup will increase core temp much higher and cause more fatigue
what is the temperature normally, in exercise, and in central fatigue ? what does this mean
36-38 normal
38-40 exercise
39.5 central fatigue
doesnt take a big increase for central fatigue
what is environmental heat stress determined by ? (4)
ambient temp
relative humidity
wind velocity
solar radiation (reflected from ground and direct)
what are the three ways heat is lost from skin by physical transfer ?
evaporation of sweat, convection, and conduction
what happens if the environment is hotter than the skin ?
heat is gained by convection and conduction , and evaporation can’t occur
what is conduction ?
transfer of heat from one to another by direct contact
what is convection ?
heat exchange between solid medium and one that moves (air/water)
evaporation of 1L water= ? kcal ?
573
if you increase the ambient temperature and/or humidity how will sweat loss, core temp, and HR change
increase
if you decrease humidity but have high ambient temp how will sweat loss, core temp, and HR change
still will increase
at the same % humidity, but different temp, how will sweat loss, core temp, and HR change
higher temp will increase the variables
skin blood flow is an example of conduction or convection ?
convection (between solid medium and something moving)
at any given intensity, in which state will body temp increase faster?
dehydrated, also will be an increase in HR
what are the two heat inputs which determine heat load ?
exercising muscle and environmental heat gain from radiation, conduction, and convection
what is radiation ?
heat exchange w emission from one and absorption from other
what two things sense the heat load ?
the core and the skin
which body part integrates the info about heat load ?
hypothalamus
what are some modifying non thermal inputs received by the hypothalamus that can regulate temp ? (5)
blood pressure osmolarity Na+/Ca2+ ratio hormones (estrogen) cytokines (IL-6)
what is IL-6’s role in modifying temp ?
raises set point temp of hypothalamus, causing rise of core temp in fever
what neurotransmitters can mediate hypothalamic sensory input ?
dopamine, serotonin, NE, and ach
what are the 5 ways that aerobic exercise from 70-100%Vo2max improves thermoregulation ? (2 blood, 3 sweating)
blood volume blood flow increased sweat gland size earlier onset of sweating increased sweat rate at a given core temperature
what relationship does dehydration upset ?
decreases sensitivity between sweat rate and core temperature, which causes fatigue and hyperthermia
what sickness happen when you can’t adapt to dehydration ?
heat illness and cramps
what is the main point of how aerobic exercise training prevents hyperthermia:
maintains body at constant temperature during exercise in heat
exercise performance is impaired when a person is dehydrated at what degree ?
loss 2% of BW or more
does dehydration also affect sprint athletes ?
yes
what is the relationship between exercise capacity and body weight loss ?
inverse / negative
the more body weight loss by dehydration, the less exercise capacity
how does dehydration affect glycogen use ?
the more dehydrated, the more the rate of glycogen use increases
this is because dehydration increases catecholamine response
how does body water loss affect Vo2max in lab or in other conditions?
body water loss higher in non-lab condition and causes a higher decrease in VO2max
what are the 4 negative and 2 positive relationships dehydration has with negative performance ?
decreased: blood volume, blood flow, sweat rate, heat dissipation
increased: core temperature, rate of muscle glycogen use
in an experiment with same people heat acclimated and unacclimated, what was found concerning core temperature ?
heat acclimation lowered core temperature when they were euhydrated compared to non-acclimated
however, when they were dehydrated, similar increases in core temperature were seen in both acclimated and non
does hypohydration affect force generation ?
yes
how does dehydration affect gastric emptying ?
reduced GE rate of ingested gluids
when should fluid consumption begin ? why ? (2)
during the early stages of exercise in the heat to minimize dehydration and also to maximize the bioavailability of digested fluids.
what is the mechanism of heat illness? talk about what happens in the blood and heart, and then what is produced and what happens to the gut
skin blood vessels dilate
pooling of blood in skin with increased heat loss
decreased central blood volume
decreased cardiac filling and stroke volume
increased heart rate to maintain same cardiac output
decrease in splanchic and renal and skin blood flow. this will all increase the core temperature
THEN, blood vessels will constrict from SNS as BP falls, meaning that ROS (reactive oxygen species) and nitric oxide (NO) will be produced, with NO being a specifically strong dilator. ROS will cause peroxidation of lipid membranes.
this will make membranes leaky; in the gut, this means more toxins will be able to come in, leading to endotoxemia (blood poisoning), and more hypotension.
consequence: organ injury, fainting
how does HR change in heat illness ? why ?
it has to increase to maintain cardiac output since SV decreases
what does ROS do ?
peroxidation of lipid membranes
what does ROS stand for ?
reactive oxygen species
what is a fancy word for blood poisoning
endotoxemia
what are risk factors for heat illness ?
dehydration hot humid climate obesity lack of acc or PA previous history no sleep medications sweat gland dysfunction upper respiratory/GI illness
why is obesity a risk factor for heat illness ?
larger body mass
how does sleep become a risk factor for heat illness
no sleep lowers HR max
which 2 medications are risk factors for heat illness
antidepressants (SSRI) and diuretics
what are the 2 most important factors in preventing heat illness ?
monitoring hydration status and promoting appropriate drinking
what is hyponatremia ?
low concentration of Na+ in blood
which population is hyponatremia most prevalent in
endurance athletes
what is the theory behind hyperhydration ?
explands blood volume which decreases plasma osmolarity, therefore improving heat dissipation
which compound is added to water for supposedly more effective hyperhydration ?
glycerol (increases fluid retention)
what is the caveat of hyperhydration studies ?
compare dehydration with hyperhydration states, while they should compare hyperhydration with euhydration
what did one hyperhydration study show about how hyperhydration can improve performance ?
increase of blood volume 400-500 mL improves cycling
how does glycerol help water absorption ? is it effective
absorbed in small intestine
increases medullary concentration in kidney, meaning you need more water absorption
effectiveness unclear
why is it unclear that glycerol helps water absorption ?
because it’s hard to control for with rate of ingestion, timing, concentration of glycerol, exercise intensity duration, etc
during exercise, how can dehydration be avoided ?
by matching fluid consumption with weight loss
why is it hard to appropriately hydrate during exercise ? (3)
sweat rates vary
thirst is not a good indicator
limited opportunity to drink in certain sports
does water intake during exercise have an effect on time to exchaustion ? performance ? in thermoneutral ? in hot ?
yes yes yes yes
do most athletes drink enough during exercise ?
no because they drink ad libitum
how does time to exhaustion change if you dont hydrate during vs water regularly ?
improved endurance
in general, what is hypotonic ?
when there is more Na+ inside the cell which attracts water inside cell meaning less in intracellular fluid
what is a hypotonic drink ?
more water proportionally than nutrients
what is an isotonic drink ?
same water proportionally than nutrients
what is a hypertonic drink ?
more nutrients proportionally than water
which type of drink will have a lower concentration of salt ?
hypotonic
classify these in terms of their ability to improve time to exhaustion : no drink, water, isotonic, hypotonic
time to exhaustion will be improved in iso and hypo»water»no drink
classify these in terms of their ability to improve time to complete the trial : large fluid + CHO, large fluid, small fluid and CHO, small fluid
less time is better
improved time in large fluid + CHO» large fluid > small fluid and CHO» small fluid
therefore adding carbs to water has a beneficial effect on performance
what are the 5 reasons that sodium and other electrolytes are added to sports drinks ?
increase palatability maintain thirst, to promote drinking prevent hyponatremia increase rate of water uptake increase fluid retention
what is the effect of too much added carb in a drink ?
concentrated hypertonic solution is bad, delays the restoration of plasma volume during exercise
at what exercise stage should you be most concerned with replacing electrolytes ?
post exercise
does fluid intake matter for very strenuous exercise under 30 min ?
no because gastric emptying inhibited at high work rates, and insignificant amount of fluid will be absorbed
describe change in plasma volume after intake of hypotonic or hypertonic drink
for both, drop in plasma volume in first 15 mini
then, hypotonic drink will positively change the plasma volume more
the hypertonic drink is more concentrated, delays gastric emptying and slows absorption
what is the major electrolyte of extracellular fluids ?
sodium
explain how type of fluid consumption before exercise may improve time to exhaustion
no drink: short time to exhaustion
15%CHO-E drink a bit better
%CHO-E drink yields the best performance
therefore, w comparable hydration status a more hypotonic drink is better
what is the normal plasma sodium concentration ?
140-144 mmol/L
what is the plasma sodium concentration in cases of symptomatic hyponatremia ?
<130 mmol/L
what is the plasma sodium concentration in cases of hyponatremia with risk of seizure, coma, death?
<120 mmol/L
in what population is hyponatremia most common ? (3)
people who don’t sweat a lot but drink large amounts of water or hypotonic fluids
women (sweat less)
people with cystic fibrosis genes (more prone to salt depletion)
as of <130 mmol/L sodium in plasma, what are some symptoms of hyponatremia ?
mental confusion, fainting, swelling of brain, edema
which hyponatremia symptoms are similar to dehydration ?
mental confusion, weakness, fainting
how often should one urinate w optimal hydration ?
1-2 hours
what kinds of foods and drinks should one abstain from to hydrate better ? (3)
caffeine, alcohol, and protein
what is the role of hydration before exercise ?
optimal sport performance with adequate hydration and fuel
what is the role of hydration during exercise ? (3)
MAINTAIN plasma volume, electrolyte balance, hydration
what are the two roles of hydration after exercise ?
replace water, electrolytes, and carbs lost
restore body to euhydration
how much fluid should be consumed 2 hrs before exercise in mL or 6-8 mL/kg BW or oz?
500 mL or 6-8 mL/kg BW or 17 oz
how much fluid should be consumed 15 min before exercise in mL?
500
when should you start drinking fluids in preparation for exercise ?
24 hours prior
which vitamins add a yellowish hue to urine ?
B
what is the best indicator of hydration status ?
urine osmolality
what are three excellent choices for fluids before exercise ?
water, juice, milk
what are 5 things positively correlated with magnitude of water and electrolyte loss
body size exercise intensity ambient temperature humidity clothing
what is one thing negatively correlated w magnitude of water and electrolyte loss
acclimation
what is the rate of how much water and electrolyte do you lose in slow pace, low intensity effort in low to moderate temperature ?
<500 mL/hr
what is the rate of how much water and electrolyte do you lose in hot and humid environment ?
2000-3000 mL/hr
what is the formula for sweat rate ?
weight loss x fluids consumed during exercise / time of exercise (hr)
what are the units of sweat rate
L/hr
how much sodium is lost in sweat ?
1g sodium = 50 mmol sodium
20-80 mmol/L = 400-600 mg/L
how much potassium is lost in sweat ?
1g potassium = 20 mmol potassium
4-8 mmol= 80-150 mg/L
how much calcium is lost in sweat ?
small amounts
at what level should athletes maintain their hydration during exercise according to the consensus ?
less than 2% reduction in body weight
most athletes will achieve the consensus hydration recommendations by doing what ?
200-300 mL every 10-20 min during exercise
what is recommended that an athlete do to know how much to drink during exercise ?
sweat trials in different environments
how does volume of fluid digested affect fluid consumption and absorption during exercise ?
increased volume facilitates euhydration by stimulating gastric emptying: most athletes do not drink enough
how does the amount of carb in drink affect fluid consumption and absorption during exercise ? what are the recommendations ?
increasing carb amount prevents GI upset and helps maintain energy and power.
recommended 1g CHO/min (the same as 1L of an energy drink)
how does carb concentration affect fluid consumption and absorption during exercise ? what happens if it increases ?
recommended 6-8% carb solution
more than 8%: decreases gastric emptying and intestinal absorption rates, causing GI disturbance
how can you determine CHO concentration in a drink ?
g CHO/240 mL x 100
how does type of carb in drink affect fluid consumption and absorption during exercise ?
recommended glucose and sucrose and glucose polymers
absorption maximized when you mix carbs
fructose not recommended
why is fructose not a good carb to include in sports drink ?
increases GI distress, but still some in sports drink for palatability
how does taste affect fluid consumption and absorption during exercise ?
flavored beverages increase fluid intake
how does exercise intensity affect fluid consumption and absorption during exercise ?
sports drinks are the recommended beverage for high intensity exercise, with CHO <7%
how do environmental conditions affect fluid consumption and absorption during exercise ?
high heat and humidity increases fluid needs, and you need CHO <7%
in which two cases are drinks with CHO <7% recommended ?
high intensity and high heat/humidity
how does altitude affect fluid consumption and absorption during exercise ?
increases fluid needs
how does colder temperature affect fluid consumption and absorption during exercise ?
colder air= drier air, water loss from humidification of passages, need more fluid
what are the two main electrolytes lost in sweat
Na and Cl
what are the Na+ intake recommendations for exercise >1hr
500-700 mg/ L water
is Na+ and Cl replacement physiologically necessary in exercise under 4 hours
no need but recommended
is Na+ and Cl replacement physiologically necessary in exercise over 4 hours
yes
what should one do in the first few days of heat acclimatization ?
may necessitate a temporary increase in sodium intake (maybe as high as 4-10g)
what are the 4 cases in which Na+ and Cl consumption during exercise is essential ?
exercise sessions > 4hrs
first acclimatization stages
ppl restricting sodium intake
ppl with not a well balanced meal before working out
what is the NATA recommendation for the 4 cases in which Na+ and Cl consumption during exercise is essential ?
add 0.3-0.7 mg sodium per L of fluid replacement, or even use salt tablets
what is the ideal temperature for a beverage
10-15 degrees
what is the protein recommendation for drinks ?
none
what is the ideal osmolality of a drink ?
hypotonic to plasma (290 mOsmol/L)
which 3 artificial sweeteners should be avoided ?
aspartame, saccharin, acesulfame potassium
which 3 drinks should be avoided bc they are stimulants ?
guarana, kola nut, caffeine
is the list of ingredients in order of weight or volume
weight
what are the 3 electrolytes we should have in beverages
Na, Cl, K
avoid products w a concentration of vitamins or minerals that___
have 10-20% DV in one serving.. this can cause GI distress. esp reconsider if 200% DV
what are 3 reasons you should avoid carbonated beverages when working out
full/bloated feeling
false sense of fullness
decrease fluid consumption
how much time does it take for ingested fluids to reach bloodstream? what does this mean ?
10-20 min so start drinking early
after how much time do you switch to sport drinks instead of water
60-90 min
what is the current recommendation for fluid after exercise
> 150% weight loss within 6 hrs post exercise
what fluids should be had after exercise ?
a meal and water
beverages like milk, soups, etc
what is the ideal beverage for post exercise replenishment containing (3)
carbs (restore muscle glycogen, increase intestinal absorption)
sodium (enhance fluid retention, restore electrolyte balance)
water
what is the recommendation for Na consumption post exercise
300-700 mg sodium/L of fluid lost in sweat
how fast should we rehydrate after exercise ?
ASAP (2 hrs after)
