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Sport nutrition (EXCI 445) > Chapter 9- Water > Flashcards

Chapter 9- Water Flashcards

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1
Q

what is the body’s principal way of getting rid of excess heat ?

A

sweating

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2
Q

who has more %plasma in their body fluid- infants, men, or women?

A

adult men and women > infants

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3
Q

in general, describe the distribution of proteins, fat, and water in babies’ bodies vs adult bodies

A

in adults, the three are more equally proportioned, but in babies, most of the body is water

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4
Q

in most people, water accounts for what % of body mass

A

50-60

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5
Q

how much water by mass in lean body tissues vs fat ?

A

75% in muscle, etc

vs 5% in fat

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6
Q

who has more %interstitial fluid in their body fluid- infants, men, or women?

A

infants > men> women

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7
Q

who has more %intracellular fluid in their body fluid- infants, men, or women?

A

infants > men > women

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8
Q

why do men have more water content ?

A

they have more lean body mass and less fat than women

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9
Q

who has more %total fluid in their body infants, men, or women?

A

infants> men> women

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10
Q

who has more %fat- infants, men, or women?

A

women > men> infants

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11
Q

what are the two variables which determine the proportion of body fluids ?

A

age and gender

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12
Q

what are the 5 functions of water

A 
resistance to temperature change
cooling 
chemical reactions
pH balance 
body fluids
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13
Q

what is the major avenue of water loss during rest ?

A

urination (60%)

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14
Q

what are the 4 avenues of water loss ?

A

urination 60% at rest
breathing
defecation
sweating

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15
Q

during exercise, how much % water loss is through sweat

A

up to 90%

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16
Q

what percent of energy is lost as heat ? what does this signify?

A

80%, meaning the body is not efficient at producing energy and using it

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17
Q

explain how 80% of energy is lost as heat

A

for every L O2, 1 cal energy is produced and 4 cal heat

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18
Q

calculate the energy made and the rate of heat production for an athlete consuming 4 LO2/min

A

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

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19
Q

where does the heat go in the body?

A

small proportion to skin, most to body core with venous blood

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20
Q

during high intensity cycling, what happens to heat flow?

A

temperature increase in quads is 1 degree celsius / min which is a lot

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21
Q

when temperature in muscle is too high, what cools it down ?

A

has to be cooled down or else contractile proteins and enzymes will denature
thermoreceptors in hypothalamus increase sweating and blood flow to skin

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22
Q

during exercise at a constant work rate, how does heat production increase ?

A

in a square wave (step) fashion.

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23
Q

when does the rise in body temperature plateau ?

A

when heat loss from body = heat production

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24
Q

what causes the increase in core temperature in exercise ? (3)

A

exercise intensity
humidity
ambient temperature

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25
Q

what is the effect of a warm up on body temperature ?

A

intense warmup will increase core temp much higher and cause more fatigue

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26
Q

what is the temperature normally, in exercise, and in central fatigue ? what does this mean

A

36-38 normal
38-40 exercise
39.5 central fatigue

doesnt take a big increase for central fatigue

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27
Q

what is environmental heat stress determined by ? (4)

A

ambient temp
relative humidity
wind velocity
solar radiation (reflected from ground and direct)

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28
Q

what are the three ways heat is lost from skin by physical transfer ?

A

evaporation of sweat, convection, and conduction

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29
Q

what happens if the environment is hotter than the skin ?

A

heat is gained by convection and conduction , and evaporation can’t occur

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30
Q

what is conduction ?

A

transfer of heat from one to another by direct contact

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31
Q

what is convection ?

A

heat exchange between solid medium and one that moves (air/water)

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32
Q

evaporation of 1L water= ? kcal ?

A

573

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33
Q

if you increase the ambient temperature and/or humidity how will sweat loss, core temp, and HR change

A

increase

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34
Q

if you decrease humidity but have high ambient temp how will sweat loss, core temp, and HR change

A

still will increase

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35
Q

at the same % humidity, but different temp, how will sweat loss, core temp, and HR change

A

higher temp will increase the variables

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36
Q

skin blood flow is an example of conduction or convection ?

A

convection (between solid medium and something moving)

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37
Q

at any given intensity, in which state will body temp increase faster?

A

dehydrated, also will be an increase in HR

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38
Q

what are the two heat inputs which determine heat load ?

A

exercising muscle and environmental heat gain from radiation, conduction, and convection

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39
Q

what is radiation ?

A

heat exchange w emission from one and absorption from other

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40
Q

what two things sense the heat load ?

A

the core and the skin

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41
Q

which body part integrates the info about heat load ?

A

hypothalamus

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42
Q

what are some modifying non thermal inputs received by the hypothalamus that can regulate temp ? (5)

A 
blood pressure
osmolarity
Na+/Ca2+ ratio
hormones (estrogen) 
cytokines (IL-6)
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43
Q

what is IL-6’s role in modifying temp ?

A

raises set point temp of hypothalamus, causing rise of core temp in fever

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44
Q

what neurotransmitters can mediate hypothalamic sensory input ?

A

dopamine, serotonin, NE, and ach

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45
Q

what are the 5 ways that aerobic exercise from 70-100%Vo2max improves thermoregulation ? (2 blood, 3 sweating)

A 
blood volume
blood flow
increased sweat gland size
earlier onset of sweating 
increased sweat rate at a given core temperature
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46
Q

what relationship does dehydration upset ?

A

decreases sensitivity between sweat rate and core temperature, which causes fatigue and hyperthermia

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47
Q

what sickness happen when you can’t adapt to dehydration ?

A

heat illness and cramps

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48
Q

what is the main point of how aerobic exercise training prevents hyperthermia:

A

maintains body at constant temperature during exercise in heat

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49
Q

exercise performance is impaired when a person is dehydrated at what degree ?

A

loss 2% of BW or more

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50
Q

does dehydration also affect sprint athletes ?

A

yes

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51
Q

what is the relationship between exercise capacity and body weight loss ?

A

inverse / negative

the more body weight loss by dehydration, the less exercise capacity

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52
Q

how does dehydration affect glycogen use ?

A

the more dehydrated, the more the rate of glycogen use increases
this is because dehydration increases catecholamine response

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53
Q

how does body water loss affect Vo2max in lab or in other conditions?

A

body water loss higher in non-lab condition and causes a higher decrease in VO2max

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54
Q

what are the 4 negative and 2 positive relationships dehydration has with negative performance ?

A

decreased: blood volume, blood flow, sweat rate, heat dissipation
increased: core temperature, rate of muscle glycogen use

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55
Q

in an experiment with same people heat acclimated and unacclimated, what was found concerning core temperature ?

A

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

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56
Q

does hypohydration affect force generation ?

A

yes

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57
Q

how does dehydration affect gastric emptying ?

A

reduced GE rate of ingested gluids

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58
Q

when should fluid consumption begin ? why ? (2)

A

during the early stages of exercise in the heat to minimize dehydration and also to maximize the bioavailability of digested fluids.

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59
Q

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

A

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

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60
Q

how does HR change in heat illness ? why ?

A

it has to increase to maintain cardiac output since SV decreases

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61
Q

what does ROS do ?

A

peroxidation of lipid membranes

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62
Q

what does ROS stand for ?

A

reactive oxygen species

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63
Q

what is a fancy word for blood poisoning

A

endotoxemia

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64
Q

what are risk factors for heat illness ?

A 
dehydration 
hot humid climate 
obesity 
lack of acc or PA
previous history 
no sleep 
medications
sweat gland dysfunction 
upper respiratory/GI illness
65
Q

why is obesity a risk factor for heat illness ?

A

larger body mass

66
Q

how does sleep become a risk factor for heat illness

A

no sleep lowers HR max

67
Q

which 2 medications are risk factors for heat illness

A

antidepressants (SSRI) and diuretics

68
Q

what are the 2 most important factors in preventing heat illness ?

A

monitoring hydration status and promoting appropriate drinking

69
Q

what is hyponatremia ?

A

low concentration of Na+ in blood

70
Q

which population is hyponatremia most prevalent in

A

endurance athletes

71
Q

what is the theory behind hyperhydration ?

A

explands blood volume which decreases plasma osmolarity, therefore improving heat dissipation

72
Q

which compound is added to water for supposedly more effective hyperhydration ?

A

glycerol (increases fluid retention)

73
Q

what is the caveat of hyperhydration studies ?

A

compare dehydration with hyperhydration states, while they should compare hyperhydration with euhydration

74
Q

what did one hyperhydration study show about how hyperhydration can improve performance ?

A

increase of blood volume 400-500 mL improves cycling

75
Q

how does glycerol help water absorption ? is it effective

A

absorbed in small intestine
increases medullary concentration in kidney, meaning you need more water absorption

effectiveness unclear

76
Q

why is it unclear that glycerol helps water absorption ?

A

because it’s hard to control for with rate of ingestion, timing, concentration of glycerol, exercise intensity duration, etc

77
Q

during exercise, how can dehydration be avoided ?

A

by matching fluid consumption with weight loss

78
Q

why is it hard to appropriately hydrate during exercise ? (3)

A

sweat rates vary
thirst is not a good indicator
limited opportunity to drink in certain sports

79
Q

does water intake during exercise have an effect on time to exchaustion ? performance ? in thermoneutral ? in hot ?

A

yes yes yes yes

80
Q

do most athletes drink enough during exercise ?

A

no because they drink ad libitum

81
Q

how does time to exhaustion change if you dont hydrate during vs water regularly ?

A

improved endurance

82
Q

in general, what is hypotonic ?

A

when there is more Na+ inside the cell which attracts water inside cell meaning less in intracellular fluid

83
Q

what is a hypotonic drink ?

A

more water proportionally than nutrients

84
Q

what is an isotonic drink ?

A

same water proportionally than nutrients

85
Q

what is a hypertonic drink ?

A

more nutrients proportionally than water

86
Q

which type of drink will have a lower concentration of salt ?

A

hypotonic

87
Q

classify these in terms of their ability to improve time to exhaustion : no drink, water, isotonic, hypotonic

A

time to exhaustion will be improved in iso and hypo»water»no drink

88
Q

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

A

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

89
Q

what are the 5 reasons that sodium and other electrolytes are added to sports drinks ?

A 
increase palatability
maintain thirst, to promote drinking
prevent hyponatremia 
increase rate of water uptake 
increase fluid retention
90
Q

what is the effect of too much added carb in a drink ?

A

concentrated hypertonic solution is bad, delays the restoration of plasma volume during exercise

91
Q

at what exercise stage should you be most concerned with replacing electrolytes ?

A

post exercise

92
Q

does fluid intake matter for very strenuous exercise under 30 min ?

A

no because gastric emptying inhibited at high work rates, and insignificant amount of fluid will be absorbed

93
Q

describe change in plasma volume after intake of hypotonic or hypertonic drink

A

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

94
Q

what is the major electrolyte of extracellular fluids ?

A

sodium

95
Q

explain how type of fluid consumption before exercise may improve time to exhaustion

A

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

96
Q

what is the normal plasma sodium concentration ?

A

140-144 mmol/L

97
Q

what is the plasma sodium concentration in cases of symptomatic hyponatremia ?

A

<130 mmol/L

98
Q

what is the plasma sodium concentration in cases of hyponatremia with risk of seizure, coma, death?

A

<120 mmol/L

99
Q

in what population is hyponatremia most common ? (3)

A

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)

100
Q

as of <130 mmol/L sodium in plasma, what are some symptoms of hyponatremia ?

A

mental confusion, fainting, swelling of brain, edema

101
Q

which hyponatremia symptoms are similar to dehydration ?

A

mental confusion, weakness, fainting

102
Q

how often should one urinate w optimal hydration ?

A

1-2 hours

103
Q

what kinds of foods and drinks should one abstain from to hydrate better ? (3)

A

caffeine, alcohol, and protein

104
Q

what is the role of hydration before exercise ?

A

optimal sport performance with adequate hydration and fuel

105
Q

what is the role of hydration during exercise ? (3)

A

MAINTAIN plasma volume, electrolyte balance, hydration

106
Q

what are the two roles of hydration after exercise ?

A

replace water, electrolytes, and carbs lost

restore body to euhydration

107
Q

how much fluid should be consumed 2 hrs before exercise in mL or 6-8 mL/kg BW or oz?

A

500 mL or 6-8 mL/kg BW or 17 oz

108
Q

how much fluid should be consumed 15 min before exercise in mL?

A

500

109
Q

when should you start drinking fluids in preparation for exercise ?

A

24 hours prior

110
Q

which vitamins add a yellowish hue to urine ?

A

B

111
Q

what is the best indicator of hydration status ?

A

urine osmolality

112
Q

what are three excellent choices for fluids before exercise ?

A

water, juice, milk

113
Q

what are 5 things positively correlated with magnitude of water and electrolyte loss

A 
body size
exercise intensity
ambient temperature
humidity
clothing
114
Q

what is one thing negatively correlated w magnitude of water and electrolyte loss

A

acclimation

115
Q

what is the rate of how much water and electrolyte do you lose in slow pace, low intensity effort in low to moderate temperature ?

A

<500 mL/hr

116
Q

what is the rate of how much water and electrolyte do you lose in hot and humid environment ?

A

2000-3000 mL/hr

117
Q

what is the formula for sweat rate ?

A

weight loss x fluids consumed during exercise / time of exercise (hr)

118
Q

what are the units of sweat rate

A

L/hr

119
Q

how much sodium is lost in sweat ?

A

1g sodium = 50 mmol sodium

20-80 mmol/L = 400-600 mg/L

120
Q

how much potassium is lost in sweat ?

A

1g potassium = 20 mmol potassium

4-8 mmol= 80-150 mg/L

121
Q

how much calcium is lost in sweat ?

A

small amounts

122
Q

at what level should athletes maintain their hydration during exercise according to the consensus ?

A

less than 2% reduction in body weight

123
Q

most athletes will achieve the consensus hydration recommendations by doing what ?

A

200-300 mL every 10-20 min during exercise

124
Q

what is recommended that an athlete do to know how much to drink during exercise ?

A

sweat trials in different environments

125
Q

how does volume of fluid digested affect fluid consumption and absorption during exercise ?

A

increased volume facilitates euhydration by stimulating gastric emptying: most athletes do not drink enough

126
Q

how does the amount of carb in drink affect fluid consumption and absorption during exercise ? what are the recommendations ?

A

increasing carb amount prevents GI upset and helps maintain energy and power.
recommended 1g CHO/min (the same as 1L of an energy drink)

127
Q

how does carb concentration affect fluid consumption and absorption during exercise ? what happens if it increases ?

A

recommended 6-8% carb solution

more than 8%: decreases gastric emptying and intestinal absorption rates, causing GI disturbance

128
Q

how can you determine CHO concentration in a drink ?

A

g CHO/240 mL x 100

129
Q

how does type of carb in drink affect fluid consumption and absorption during exercise ?

A

recommended glucose and sucrose and glucose polymers
absorption maximized when you mix carbs
fructose not recommended

130
Q

why is fructose not a good carb to include in sports drink ?

A

increases GI distress, but still some in sports drink for palatability

131
Q

how does taste affect fluid consumption and absorption during exercise ?

A

flavored beverages increase fluid intake

132
Q

how does exercise intensity affect fluid consumption and absorption during exercise ?

A

sports drinks are the recommended beverage for high intensity exercise, with CHO <7%

133
Q

how do environmental conditions affect fluid consumption and absorption during exercise ?

A

high heat and humidity increases fluid needs, and you need CHO <7%

134
Q

in which two cases are drinks with CHO <7% recommended ?

A

high intensity and high heat/humidity

135
Q

how does altitude affect fluid consumption and absorption during exercise ?

A

increases fluid needs

136
Q

how does colder temperature affect fluid consumption and absorption during exercise ?

A

colder air= drier air, water loss from humidification of passages, need more fluid

137
Q

what are the two main electrolytes lost in sweat

A

Na and Cl

138
Q

what are the Na+ intake recommendations for exercise >1hr

A

500-700 mg/ L water

139
Q

is Na+ and Cl replacement physiologically necessary in exercise under 4 hours

A

no need but recommended

140
Q

is Na+ and Cl replacement physiologically necessary in exercise over 4 hours

A

yes

141
Q

what should one do in the first few days of heat acclimatization ?

A

may necessitate a temporary increase in sodium intake (maybe as high as 4-10g)

142
Q

what are the 4 cases in which Na+ and Cl consumption during exercise is essential ?

A

exercise sessions > 4hrs
first acclimatization stages
ppl restricting sodium intake
ppl with not a well balanced meal before working out

143
Q

what is the NATA recommendation for the 4 cases in which Na+ and Cl consumption during exercise is essential ?

A

add 0.3-0.7 mg sodium per L of fluid replacement, or even use salt tablets

144
Q

what is the ideal temperature for a beverage

A

10-15 degrees

145
Q

what is the protein recommendation for drinks ?

A

none

146
Q

what is the ideal osmolality of a drink ?

A

hypotonic to plasma (290 mOsmol/L)

147
Q

which 3 artificial sweeteners should be avoided ?

A

aspartame, saccharin, acesulfame potassium

148
Q

which 3 drinks should be avoided bc they are stimulants ?

A

guarana, kola nut, caffeine

149
Q

is the list of ingredients in order of weight or volume

A

weight

150
Q

what are the 3 electrolytes we should have in beverages

A

Na, Cl, K

151
Q

avoid products w a concentration of vitamins or minerals that___

A

have 10-20% DV in one serving.. this can cause GI distress. esp reconsider if 200% DV

152
Q

what are 3 reasons you should avoid carbonated beverages when working out

A

full/bloated feeling
false sense of fullness
decrease fluid consumption

153
Q

how much time does it take for ingested fluids to reach bloodstream? what does this mean ?

A

10-20 min so start drinking early

154
Q

after how much time do you switch to sport drinks instead of water

A

60-90 min

155
Q

what is the current recommendation for fluid after exercise

A

> 150% weight loss within 6 hrs post exercise

156
Q

what fluids should be had after exercise ?

A

a meal and water

beverages like milk, soups, etc

157
Q

what is the ideal beverage for post exercise replenishment containing (3)

A

carbs (restore muscle glycogen, increase intestinal absorption)
sodium (enhance fluid retention, restore electrolyte balance)
water

158
Q

what is the recommendation for Na consumption post exercise

A

300-700 mg sodium/L of fluid lost in sweat

159
Q

how fast should we rehydrate after exercise ?

A

ASAP (2 hrs after)

Sport nutrition (EXCI 445) (17 decks)

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