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Exercise Physiology > Chapter 12 & 23 > Flashcards

Chapter 12 & 23 Flashcards

1
Q

humans are

A

homeotherms
*maintain constant body core temperature through metabolic heat production
*heat loss must match heat gain so that we avoid increases in body temperature

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2
Q

normal core temperature

A

37C

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3
Q

temperatures above 45C

A

can damage proteins and enzymes can lead to death

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4
Q

temperatures below 34C

A

can result in decreased metabolism and cardiac arrythmias

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5
Q

thermal gradients

A

exists between deep body core to skin surface
- typical gradient is 4C
-in extreme cold may be 20C

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6
Q

what measures deep body (core) temperature

A

ingestible temperature pill

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7
Q

what measures skin (shell) temperature

A

thermistors at various locations and can calculate mean skin temperature

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8
Q

voluntary heat production

A

exercise
70-80% EE released as heat (metabolism) dependent on efficiency

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9
Q

involuntary heat production

A

shivering - increases heat production by ~5x
non-shivering thermogenesis - in brown adipose tissue (mediated by thyroxine and catecholamines)

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10
Q

mechanisms of heat loss/transfer

A

evaporation
radiation
conduction
convection

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11
Q

evaporation

A

primary mechanism in hot environments
body heat causes sweating which is lost from the body surface when changed from a liquid to a vapor

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12
Q

radiation

A

body heat loss to nearby objects without physically touching them

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13
Q

convection

A

body heat is lost to convection which becomes warmer, rises and is replaced with cooler air

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14
Q

conduction

A

body heat is lost to nearby objets through direct physical touch

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15
Q

evaporation rate depends on

A

temperature and relative humidity
convective currents around the body (fan vs no fan)
amount of skin surface exposed

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16
Q

high relative humidity decreases the vapor pressure gradient between the skin and the environment leading to

A

less evaporation

  • the warmer = increased vapor pressure = less evaporation
  • the more humid = increased water molecules in the air = decreased evaporation
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17
Q

heat index

A

measurement of body’s perception of how hot it feels

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18
Q

high relative humidity does what to evaporative heat loss

A

decreases it and increases the perception of how hot it feels

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19
Q

POAH (preoptic anterior hypothalamus)

A

body’s thermostat
* responds to increased core temperature

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20
Q

increased core body temperature causes

A

the POAH to stimulate the sweat glands for evaporative heat loss as well as cutaneous vasodilation to the periphery

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21
Q

how does the POAH stimulate sweat glands and cutaneous vasodilation

A

via sympathetic cholinergic control of sweat glands and cutaneous vasculature

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22
Q

stimulation of sweating mechanism

A

in eccrine sweat glands, stimulation occurs via activation by ACh, which binds to mACHR
ACh binding to mACHR causes vasodilation of blood vessels in the skin

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23
Q

as exercise intensity increases, what thermal events occur

A

heat production increases due to muscular contraction (metabolism)
linear increase in body temperature (core body temperature increases proportional to active muscle mass)

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24
Q

what determines heat production during steady state exercise

A

EXERCISE INTENSITY
NOT environmental temperature

different work rates = different heat production

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25
Q

submaximal exercise in a hot/humid environment causes

A

higher core temperature which increases risk for hyperthermia and heat injury because no longer can rely on evaporation

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26
Q

heat illnesses : severity

A

heat cramps (1st) - thirst, sweating, etc
heat exhaustion (2nd) - headache, nausea, chills
heat stroke (3rd) - no sweating, confusion, loss of consciousness

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27
Q

cardiovascular responses to exercise in the heat

A

upward drift in VO2 during prolonged exercise in a hot and humid environment

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28
Q

how is cardiac output maintained in hot and humid environments

A

heart rate gradually increases to help compensate for the decrease in SV

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29
Q

what happens to blood flow in hot and humid environments

A

blood flow is shunted AWAY from working muscle and nonessential areas (gut, liver, and kidneys) and goes to the skin

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30
Q

sweat rates during exercise

A

higher sweat rate - 4/5 L per hour (larger individuals will sweat more and genetics)

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31
Q

endocrine responses to exercise in the heat

A

loss of blood volume causes increased release of vasopressin and aldosterone which helps retain blood volume
* this is easier at rest and harder during exercise

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32
Q

factors that contribute to impaired exercise performance in the heat

A

1) CNS dysfunction
2) Cardiovascular dysfunction
3) accelerated muscle fatigue

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33
Q

CNS dysfunction that leads to impaired exercise performance in the heat

A

decreased motivation
reduced voluntary activation of motor units

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34
Q

cardiovascular dysfunction that leads to impaired exercise performance in the heat

A

reduced SV
decreased Q during high intensity exercise
decreased muscle blood flow

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35
Q

accelerated muscle fatigue leading to impaired exercise performance in the heat

A

increased radical production
decreased muscle pH
muscle glycogen depletion

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36
Q

acclimation

A

rapid biological adaption that occurs within days to a few weeks or is artificially induced in a climactic chamber

in a lab

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37
Q

acclimitization

A

gradual LONG TERM adaptation that occurs within months to years of exposure to environmental stress *climate

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38
Q

what do heat adaptations such as acclimation and acclimitization require

A

requires exercise in hot environments to elicit a response
*elevated core temperature promotes adaptations

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39
Q

impact of heat acclimation/acclimitization

A

lower heart rate and core temperature during submaximal exercise

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40
Q

adaptations during heat acclimation

A

1) increased plasma volume (10-12%)
2) earlier onset of sweating and higher sweat rate
3) reduced sodium chloride loss in sweat
4) reduced skin blood flow
5) increased HSP

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41
Q

increased plasma volume results in

A

maintains blood volume, SV, and sweating capacity

42
Q

earlier onset of sweating and higher sweat rate results in

A

less heat storage, maintain lower body temperature

43
Q

reduced sodium loss in sweat results in

A

reduced risk of electrolyte disturbance via enhanced aldosterone release

44
Q

reduced skin blood flow helps

A

body sweat earlier and cool down faster
better equipped to handle core body temperature

45
Q

increased cellular HSP results in

A

prevention of cellular damage due to heat
protects cells from thermal injury by stabilizing and refolding damaged proteins

46
Q

number of days required for heat acclimation

A

HR decrease and plasma volume increase happens quickly (within 6-8 days)
then RPE decrease
last== sweat rate adaptation

47
Q

sex and age differences in thermoregulation

A

sex differences are small when matched for body composition and level of acclimation

aging results in reduced ability to lose heat during exercise because skin blood flow is reduced in older individuals (ability to vasodilate decreases as we age)

48
Q

loss of acclimation

A

lost within a few days of inactivity (no heat exposure)

  • significant decline in 7 days (hard to maintain high blood volume if not constantly stressed)
  • complete loss of adaptations in 28 days
49
Q

PAOH role in cold weather

A

responds to DECREASED core temperature
causing:
shivering and decreased skin blood flow (shunting heat to the core)

50
Q

shivering

A

if core temperature drops significantly, involuntary shivering begins
somatic motor neurons release ACh and stimulates skeletal muscle contraction which helps in heat production

51
Q

non-shivering thermogenesis

A

the POAH initiates the release of NE/thyroxine which increases the rate of cellular metabolism to create heat and increase body temperature

52
Q

how does NE cause vasoconstriction of the blood vessels in the skin

A

acts on alpa-1 ADR

53
Q

exercise in the cold environment results in

A

enhanced heat LOSS to the environment
may result in hypothermia which causes loss of judgment and risk of further cold injury

54
Q

insulating factors that help maintain body heat

A

subcutaneous fat
- especially effective in cold water
- fat is the primary fuel for shivering in well fed individuals

55
Q

changes in insulation required during exercise

A

lower insulation is needed during exercise

56
Q

rate of heat loss is influenced by what environmental factor

A

windchill index

57
Q

effect of water temperature on survival

A

water immersion causes a rate of heat loss 25x greater than air of the same temperature

*heat dissipates in water fast

58
Q

cardiovascular responses to exercise in the cold

A

blood flow is shunted AWAY from the SKIN and towards the core via cutaneous vascoCONSTRICTION

59
Q

muscle function in a cold environment

A

impaired
hands exposed to cold temps often become numb due to reduced blood flow and depressed rate of neural transmission (because all heat kept in core)

reduction in neural transmission and blood flow to hands results in loss of dexterity and negatively impacts motor skills

60
Q

endocrine responses to exercise in the cold

A

in response to the cold there is an increased release of NE/E and thyroxine for metabolic heat production via increased non-shivering thermogenesis

61
Q

health risks during exercise in the cold

A

individuals immersed in cold water (15C and below) are at risk for hypothermia
** when body temperature declines from 37C to 25C or lower, this level of hypothermia is associated with life threatening cardiac arrhythmias

62
Q

exercise in cold water vs cold air

A

cold water = increased risk for hypothermia
cold air= less risk

63
Q

exercise in cold air:

A
  • exposed skin is at risk for frostbite when air temps below freezing
  • breathing cold air during exercise DOES NOT pose a risk to respiratory tract or lungs because the air is rapidly warmed before entering the lungs
  • breathing cold air can trigger exercise induced asthma in some individuals because of cooling and drying of airways
64
Q

cold acclimation

A

1) results in lower skin temperature at which shivering begins
2) maintain higher hand and foot temperature
3) improved ability to sleep in the cold

65
Q

lower skin temperature at which shivering begins due to

A

increased non-shivering thermogenesis

66
Q

maintain higher hand and foot temperature due to

A

improved peripheral blood flow

67
Q

improved ability to sleep in the cold due to

A

reduced shivering

68
Q

how do cold-acclimatized people maintain body heat with less shivering

A

by increasing non-shivering thermogenesis

69
Q

sex responses to cold exposure : at rest

A

women show a faster reduction in body temperature than men

70
Q

sex responses to cold exposure : in cold water

A

decreased body temperature is similar in men and women (due to heat dissipation properties in water)

71
Q

sex responses to cold exposure differences can be explained by

A

body composition and anthropometry
(decreased in lean muscle mass and body size)

72
Q

age responses to cold exposure

A

older than 60 years less tolerant to cold
children experience faster fall in body temperature

73
Q

dalton’s law

A

the total pressure of a gas mixture is = to the sum of the pressure that each gas would exert independently

basically partial pressure (sum of all gasses pressure in air)

74
Q

as we increase in altitude, what happens

A

the % of O2 stays the SAME
the total # of O2 molecules is different

75
Q

going from sea level to pikes peak

A

decreased diffusion gradient of O2
= cant drive O2 into tissues since PO2 is lower

76
Q

effects of altitude on Hb-O2 curve

A

hypoxia = shift left (low O2/altitude)
hyperoxia- shift right (high PO2)

77
Q

arterial O2 content is made of

A

SaO2
[Hb]
partial pressure of O2 in arteries

78
Q

what happens to VO2 max at altitude

A

decreased

79
Q

trained vs untrained VO2 at altitude

A

trained individuals have a LARGER decline because they have a larger capacity (VO2 max) and increase in SV, decrease in PaO2, and capillary transit time decreases

80
Q

HR responses to altitude during submaximal exercise

A

HR increases

81
Q

Ve response to submaximal exercise at altitude

A

Ve increases due to peripheral chemoreceptors sensing lower PO2

  • at altitude, ventilatory drive is primarily induced by changes in PO2 whereas at rest it is normally controlled by PCO2 and pH
82
Q

Lower PO2 (altitude) effects on short term anaerobic performance

A

should have no effect on performance because for short term exercises we are normally relying on non-oxidative sources so O2 transport to muscle would NOT limit performance
*lower air resistance may improve performance

83
Q

lower PO2 (altitude) effects on long term aerobic performance

A

Lower PO2 results in poorer aerobic performance because long duration exercises mostly reliant on O2 sources and are dependent on O2 delivery to muscle

84
Q

cardiovascular responses to altitude

A

decreased plasma volume upon initial arrival to altitude which decreases SV due to increased RWL and UWL which increases hematocrit

85
Q

after a few weeks at altitude what is the CV response

A

diminished plasma volume will return to normal if adequate fluid ingested

86
Q

acclimatization to altitude

A

1) production of more red blood cells
2) greater O2 saturation
3) hyperventilation

87
Q

how are more RBC’s produced via EPO

A

higher RBC concentration via EPO from the kidneys

88
Q

what is greater O2 saturation due to

A

an increase in blood flow to the lungs

89
Q

what population produces more RBCs in response to high altitude

A

andeans adapt to high altitude by producing more RBCs to counter the desaturation caused by lower PO2

*they have an average hematocrit of 60-65% when normally we have 45%

90
Q

function of EPO

A

decreased blood O2 stimulates the kidneys to release EPO which targets the red bone marrow causing increased RBC production which overall increases blood O2

91
Q

what is hyperventilation due to at altitude

A

increased sensitivity of carotid chemoreceptor which responses to changes in CO2 (pH) and O2 (ventilation)

92
Q

what populations exhibit greater O2 saturation due to altitude

A

tibetan high altitude residents (Sherpas) have NO increase in hematocrit but adapt by INCREASING THE O2 SATURATION of existing Hb via increased blood flow to the lungs due to high NO

NO (nitric oxide) = vasodilation = increased blood flow to lungs = increases V/Q relationship

93
Q

lifetime altitude residents

A

have complete adaptations in arterial O2 content and VO2 max

  • adaptations are less complete in those arriving at altitude later (sea level = decreased adaptations)
  • moderate/high altitude = increased adaptations which could lead to increased NO or hematocrit
94
Q

if you live at high altitude how should you train

A

at low altitude
which helps maintain high interval training velocity
* some athletes may still experience Hb desaturation

95
Q

living at high altitude results in

A

an increase in RBC mass via EPO = increase in VO2max
>22 hr/day at 2,000-2,500 m required or do intermittent hypobaric hypoxia

96
Q

improvement in race times in runners due to change in altitude in which they lived

A

sea level residents lived at 2,500 (altitude) and trained at altitude for 27 days
their 3000 m time trial performance increased by 1.1% and VO2 max increased by 3.2% as a result of intervention

97
Q

if a sea level athlete moves to altitude to train and moves back to sea level what happens

A

some athletes will have a higher VO2 max upon return to low altitude while others will not
* could be due to detraining effect - cannot train as intensely at altitude

98
Q

increased RBC mass leads to

A

increased VO2 max

99
Q

can you have an improved VO2 max without increased RBC mass

A

controversial but some studies show an increased RBC mass is necessary but not sufficient for improved performance

100
Q

effects of living Low, and training high

A

avoids negative effects of prolonged altitude exposure
no real changes in VO2 max or Hb concentration

Exercise Physiology (8 decks)

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