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Extreme environments > Heat > Flashcards

Heat Flashcards

(62 cards)

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1
Q

Locations to measure body core temp

A

oesophageal
rectal (most common)
gastro intenstinal
tympanic - ear
infrared camera
sublingual

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2
Q

When does set point for body core temp change?

A

exercise
climate

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3
Q

Set point body core temp

A

37

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4
Q

How to measure skin temp

A

weighted mean - at min 4 sites
thermocouples (wires)
ibuttons (wireless)
infrared thermography - radiating energy released from body

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5
Q

How to measure sweat rate

A

body mass change - respiratory loss and metabolic exchange
ventilated capsule - thermoreg control/kinetics
patch collection - dietary Na+ loss

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6
Q

Heat stress indexes

A

air temp
mean radiant temp
humidity
air velocity
clothing
metabolic rate

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7
Q

Heat balance equation

A

s = m - w +/e +/c +/r +/k

w.m-2

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8
Q

Environmental parameters

A

ambient temp
humidity
air velocity
solar radiation

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9
Q

Heat exchange pathways

A

diffused radiation
direct radiation
radiation
reflected radiation

convection
wind
conduction

evaporation

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10
Q

Personal factors affecting heat balance

A

age
biological sex
body surface area
aerobic fitness

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11
Q

Task dependant factors affecting heat balance

A

rate of metabolic heat production
clothing

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12
Q

What happens when body temp increases

A

afferent to brain
efferent to muscles

blood vessels dilate
sweat glands secrete fluid
= heat lost to environ

body temp return to normal

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13
Q

What happens when body temp decreases

A

body temp falls

afferent to brain
efferent to muscles

blood vessels constrict
sweat glands do not secrete fluid
= heat conserved

shivering generates heat
= heat retained

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14
Q

What happens when mean body temp increases?

A

increase in body temp occurs before the effector response is activated at a given onset threshold

effector output increases proportionally to increase body temp

plateau occur when effector outputs reach maximal values

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15
Q

Is skin temp regulated?

A

no
varies across the body in response to thermal environ
unevenly thermosensitive

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16
Q

Sweating response pattern

A

steep rise to own plateau
non-uniformity in sweat rates

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17
Q

Heat loss during exercise via

A

sweat evaporation
only way if environ temp exceed skin temp

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18
Q

Heat source during exercise

A

active skeletal muscle
increase in hot environ due to impaired heat conduction

start = intramuscular temp increase rapidly
more uniformed as continue

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19
Q

What is the risk of heat-related illness driven by?

A

heat exposure
from ambient heat stress and internal metabolic energy production

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20
Q

2 types of heat stroke

A

classic
exertional

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21
Q

Individual susceptability risk factors

A

age
coexisting conditions
pregnancy
medications or drugs
cognitive impairments
disabilities
social isolation
immibility

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22
Q

Heat exposure risk factors

A

ambient temperature and humidity
heat amplification
occupation (outdoor or indoor without cooling)
lack of access to cooling at home
indoor heat sources

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23
Q

Sociocultural risk factors

A

poverty
structural and environmental racism
social cohesion
housing status
literacy
limited worke protections

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24
Q

Exertional heat stroke

A

CNS disorder
high core temp
tissue and organ damage
endotoxaemia

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25
Signs/symptoms early stages
disorientation tachycardia vomiting seizures loss of balance coma
26
Signs/symptoms late stages
rhabdomyolysis circulatory failure multiorgan failure disseminated intravascular coagulation
27
What is the second most common non-traumatic death in competitive athletes?
exertional heat stroke
28
Exercise-induced dehydration
induces intracellular and extracellular fluid loss in proportion to the loss of water and solutes
29
Hypernatremia
plasma sodium conc 145mmol.L-1 (high) hyperpnea restlessness lethargy coma
30
Hyponatremia
plasma sodium conc 135mmol.L-1 or less (low) due to increase in total body water relative to amount of total body exchangeable sodium
31
Symptomatic hyponatremia
headache vomiting altered metal status - confusion/seizure cerebral edema = death
32
What does the capacity of the environ to absorb heat depend on?
water vapour pressure (wet bulb) radient temp (direct solar) air movement (relative to skin surface) resistance to heat transfer (clothing,postur) ambient temp (dry bulb)
33
Hot/humid conditions
harder to offload heat if low evaporative capacity requires more sweat/skin blood flow
34
Why quantify heat stress?
assess clothing systems hydration regimes safety of exercise in warm or cold environ
35
Things to consider in selecting thermoregulatory measures:
sensitivity (detect change?) practicality (cost) usability (safe) reliability validity
36
Treatment exertional heat stroke
remove from heat cool (whole body immersion ideal) hydrate
37
Heat stress and associated hyperthermia shown to:
reduce time to exhaustion during constant work rate exercise progressive decrease in work rate during self-paced exercise reduced max aerobic power (VO2max)
38
What impaires performance?
high skin temp high blood flow
39
What impairs endurance performance in the heat?
cardiovascular strain HRmax reached at lower work rate + lower SV = decrease max CO impairs O2 delivery functional limit of cardiovascular system
40
Critical core temp
trigger premature fatigue by reducing mental drive (motivation) for motor performance acting as safety break for catastrophic hyperthermia (cellular and CNS damage)
41
Perturbations in skeletal muscle function
prolonged exercise in heat increases muscle glycogen utilization andanaerobic metabolism = greater accumulation of ammonia and muscle lactate
42
Physiological demands of exercise in heat
need increase muscle blood flow = need increase skin blood flow (offload heat to prevent hyperthermia) maintain arterial pressure adequate blood supply to other tissues CNS
43
Order of priority for regulation during exercise
1. blood pressure 2. metabolism 3. body temp (risk for heat injury)
44
Dehydration
decrease plasma volume increase plasma osmolality
45
What can a rise in sweat rate lead to?
progressive dehydration = more rapid increase in core temp = affect performance
46
Plasma hyperosmolality
reduces sweat rate decreases evaporative heat loss
47
How can single-sprint performance be improved?
passive local muscle heating (warm baths/heated blankets) active warm-up passive heating (elevation of core temp by 1) hot ambient conditions
48
Heat-related mechanisms contributing to sprint improvements:
faster rate of PCr utilisation greater ATP turnover and adenine nucleotide degradation accelerated muscle fibre conduction velocity
49
Optimise performance weeks/days
training acclimation acclimatisation
50
Optimise performance hours/mins
hydration pre-cooling
51
Optimise performance during
clothing hydration pacing cooling
52
Acclimation
several consecutive days of heat exposure artificial, periodic exposures
53
Acclimatisation
requires several consecutive days of heat exposure natural, periodic exposures
54
Heat adaptations of core temp
decrease resting body temp = more heat can be stored decrease exercising cor temp
55
What does heat acclimation do?
increases onset threshold, sensitivity and max capacity of sweating and skin blood flow responses
56
Heat acclimation increases total body water
rapid increase in plasma volume expansion increase secretion or renal sensitivity to fluid regulatory hormones and proteins (aldosterone, vasopressin, albumin) increasing renal retention of water and electrolytes changing the oncotic pressure and drwing fluid into the intravascular space
57
Heat acclimation changes sweat composition
reduces sweat Na+, Cl- and K+ loss
58
Heat adaptation of cardiovascular responses
increase blood volume decrease HR at rest? and during exercise increase SV during exercise = reduce cardiovascular strain during exercise in heat
59
Heat shock proteins
heat acclimation increase expression of HSPs provide cytoprotection protecting and accelerating repair from heat stress
60
Heat acclimation may alter substrate metabolism via:
glycogen sparing increasing lactate threshold reduce lactate conc during exercise improved economy
61
Heat acclimation can:
reduce thermal discomfort reduce rating of perceived exertion
62
Classic markers of heat acclimation
plasma volume expansion decrease core temp decrease heart rate increase sweat rate improved thermal comfort

Extreme environments (1 decks)

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