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Environmental Physiology Midterm > Heat > Flashcards

Heat Flashcards

1
Q

Who does heat affect the most

A

Military
Athletes
Heat waves

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2
Q

Heat and athletes

A

Heat stroke is the third leading cause of death behind cardiac disorders and head + neck trauma

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3
Q

Shape of our body and heat

A

Designed to move efficiently (slowly) and dump heat

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4
Q

How to quantify internal severity of stress

A

Direct or indirect calorimetry (ideal)
Guesstimate using formulae for energy cost of activities (crude)

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5
Q

How to quantify external severity of stress

A

Use a rational index of the environmental stress (based on thermodynamics)
Use an empirical index (usual) based on cumulated lab data of peoples’ responses to a variety of environments

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6
Q

Implications of heat balance equation

A

Can determine person’s ability to sustain exercise
Can use it to predict exercise safety and exposure times

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7
Q

Sensible heat loss (dry)

A

Dominates in cold environment

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8
Q

Insensible heat loss (wet)

A

Dominates if temperature increases from exercise intensity

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9
Q

Core temperature response to exercise

A

Increases as a function of the metabolic rate
Increases almost immediately

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10
Q

What happens when core temperature rises

A

Heat-dissipating reflexes are elicited
Rate of heat storage decreases
Core temperature rises more slowly

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11
Q

What happens to heat dissipation as exercise continues

A

Heat dissipation balances heat production or heat intolerance ensues

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12
Q

Exercise training in a temperature climate

A

Reduces physiologic strain in the heat
Improves exercise capabilities in the heat

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13
Q

Exercise training in a hot climate

A

Induces biologic adjustments that reduce the negative effects of heat stress
Develops through repeated heat exposures that are stressful to elevate both core and skin temperatures and provoke profuse sweating

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14
Q

Biological adjustments are mediated by

A

integrated changes in thermoregulatory control
Fluid balance
Cardiovascular responses

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15
Q

Sweating power variability

A

Forehead and dorsal hands > torso and arms > lower limbs

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16
Q

Can sweating power increase?

A

Yes, can double sweating power with training and heat acclimation

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17
Q

Magnitude of biologic adaptations induced by heat acclimatization depends on

A

Intensity
Duration
Frequency
Number

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18
Q

Heat acclimatization up keep

A

Transient and gradually disappears if not maintained by repeated heat exposure

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19
Q

Types of heat illness in order of severity

A

Heat exhaustion
Heat injury
Heat stroke

20
Q

Heat exhaustion

A

Mild to moderate illness
Inability to sustain cardiac output
>38.5- 40 body temperature
Resulting from strenuous exercise and environmental heat exposure
Accompanied by hot skin and dehydration

21
Q

Heat injury

A

Moderate to severe illness
Organ or tissue injury
High body temperature >40
Resulting from strenuous exercise and environmental heat exposure

22
Q

Heat stroke

A

Severe illness
Profound CNS dysfunction, organ or tissue injury
High body temperatures
Resulting from strenuous exercise and environmental heat exposure
Can result in profound neuropsychiatric impairments
Can be complicated by liver damage, rhabdomyolysis

23
Q

Cardiac output equation

A

CO = Stroke volume (SV) x Heart rate (HR)

24
Q

Mean arterial pressure equation

A

MAP = CO x total peripheral resistance (TPR) - ohms law
MAP = (SV x HR) x TPR

25
Q

Describe peripheral vasodilation during heat stress

A

Dramatically decrease TPR. To maintain MAP, CO must increase with heat stress. If CO cant be sustained, heat gain ensues

26
Q

Frank-sterling relation in heat stress

A

Reduced venous return from blood pooling in the skin lead to reductions in CVP
Shifts the operating point to a steeper slope
Increased contractility of the heart

27
Q

What happens during heat stress

A

Increase skin blood flow and increase sweating
Decrease central blood volume
Decrease brain blood flow
Hyperventilatory induced hypocapnia

28
Q

Most effective cooling techniques

A

IV or intra arterial (most effective)
Whole-body or partial water/ice immersion

29
Q

Other cooling techniques

A

Ice-slurry ingestion
Ice vests
Fanning (effectiveness varies with environment)

30
Q

Is face best place to apply cooling?

A

May have most impact on comfort
Will create false perception of thermal state

31
Q

What does precooling do

A

Increase time to critical core
Increase work rate
Increase heat storage capacity
Thermal comfort improved
Thermal sensitivity altered
Fatigue triggers delayed
Sweat production

32
Q

Main factors governing performance in the heat

A

Aerobic fitness
Acclimation or acclimatization
Hydration
Thermal status
CHO availability

33
Q

How does aerobic fitness increase performance and tolerance in the heat?

A

Decreases core temperature at rest and submax
Sweat rate and skin blood flow
Perfusion of ‘non-essential’ tissues

34
Q

How can thermoregulation be impaired?

A

Spinal cord injury, babies and elderly

35
Q

Spinal cord injury thermoregulation impairment

A

Many afferent and efferent functions impaired

36
Q

Baby thermoregulation impairment

A

Increase area:mass ratio
Increased head area
Decreased behaviour

37
Q

Elderly thermoregulation impairment

A

Decreased thermoafferent input
Decreased thermal mass (body mass)
Medications that impair thermoregulation
Decreased vasoconstriction
Slower rehydration

38
Q

Athlete considerations during heat

A

Weather (humidity, solar radiation)
Time of the day of competition
Several events per day
Heat acclimatization and hydration strategies

39
Q

Para-athletes - Spinal cord injury

A

Reduced afferent input to thermoregulatory centres
Sympathetic innervation to eccrine sweat glands exit the spinal cord at T1 - L2
Attenuated sympathetic vasoconstriction and skeletal muscle pump (reduced ability to redistribute blood flow)

40
Q

Para-athletes - cerebral palsy

A

Impaired muscular coordination and movement efficiency; higher metabolic cost and thus thermal strain for a given exercise intensity

41
Q

Para-athletes - multiple sclerosis

A

Heat intolerance/sensitivity due to demyelination of conduction pathways within the CNS

Impaired sensory and effector responses

42
Q

Para-athletes - amputation

A
  • Reduced BSA for convective and evaporative heat loss
  • Gait asymmetries elevating heat production
  • Reduced heat dissipation and increased heat storage during exercise due to prosthetic coverings
  • Skin grafts on amputated limb impair heat dissipation due to absence of sweat gland responsiveness or impaired cutaneous vasodilatory capacity
  • Thermal discomfort and skin blisters due to sweat between limb and prosthetic
43
Q

Para-athletes - visual impairment

A

Unable to rely on visual feedback and cues to adapt pacing

Unable to self-check hydration status via urine volume and colour

44
Q

Controlled _____ and ______ is good

A

Heat and shear stress (blood flow)

45
Q

How to attenuate age-related declines in function

A

Establish good heat therapy habits

Environmental Physiology Midterm (4 decks)

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