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Exercise Physiology > 12 - Exercise in Hot and Cold Environments > Flashcards

12 - Exercise in Hot and Cold Environments Flashcards

1
Q

How do humans regulate temperature?

A

Humans are homeothermic
- Internal body temperature is regulated and nearly constant despite environmental temperature changes
- Thermoregulation

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2
Q

What is thermoregulation?

A

The regulation of body temperature around a physiological set point

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3
Q

What is acclimation?

A

Short-term adaptation to environmental stressor (days or weeks)

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4
Q

What is acclimatization?

A

Long-term adaptation to environmental stressor (months or years)

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5
Q

What is metabolic heat production?

A

< 25% of ATP breakdown leads to cellular work (W)
> 75% of ATP breakdown leads to metabolic heat

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6
Q

Body and environment heat relationship

A

Transfer of heat between body and environment
- heat moves from body core tom body shell via blood
- when heat reaches skin, it can be dissipated into the environment

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7
Q

How is heat lost from the body?

A

through conduction, convection, radiation or evaporation

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8
Q

How is heat gained?

A
  1. metabolic heat
  2. environmental heat (conduction, convection and radiation)
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9
Q

What is conduction (K)?

A
  • heat transfer from one solid material to another through direct molecular contact (negligible)
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10
Q

Example of conduction

A

sitting on cold or hot metal bleachers

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11
Q

What is convection (C)?

A
  • heat transfer by movement of gas or liquid across a surface
  • increase of movement across skin surface increases heat exchange
  • major thermoregulatory factor
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12
Q

What is radiation (R)?

A
  • heat loss in the form of infrared rays
  • body able to give off or receive radiant heat
  • major thermoregulatory factor
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13
Q

What is convection, conduction and radiation avenues for?

A

dry heat exchange

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14
Q

What is insulation (I)?

A

Resistance to dry heat exchange

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15
Q

What is evaporation (E)?

A
  • heat loss via phase change from liquid to gas
  • primary heat loss during exercise (80%)
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16
Q

What resists evaporation?

A

Clothing

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17
Q

Heat balance equations

A

if equa = 0 -> heat balance
if equa < 0 -> heat loss
if equa >0 -> heat gain

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18
Q

Humidity related to evaporation

A

increase in humidity = decrease in evaporation
(inverse relationship)

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19
Q

What causes dehydration?

A

prolonged evaporation via sweat

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20
Q

Cooling capacity of sweat

A
  • if air temperature is > or = skin temperature, cooling will not work so the body depends on evaporation
  • 1.5L of sweat evap cools 400W
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21
Q

What body temps can the body briefly withstand?

A

< 35 degress and >41 degrees

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22
Q

What temp is core temperature regulated around?

A

37 degrees celcius

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23
Q

What is thermoregulatory function controlled by?

A

POAH

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24
Q

What is Preoptic - anterior hypothalamus (POAH)?

A
  • The body’s thermostat is found in the brain
  • receives input from sensory thermoreceptors
  • when body temp deviates, POAH activates thermoregulatory mechanisms
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25
Q

Sensory (thermo) receptors (2 types)

A
  • peripheral thermoreceptors found in the skin
  • central thermoreceptiors in the brain and spinal cord
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26
Q

What happens during thermoregulatory control?

A
  • POAH signals sympathetic nervous system effectors activate different parts of the body to regulate temp.
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27
Q

What do skin arteriole effectors do?

A
  • SNS vasocontricts to minimize heat loss
  • SNS vasodilates to enhance heat loss
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28
Q

What do endocrine sweat gland effectors do?

A

SNS stimulates sweating where sweat evaporizes losing heat
- more responsive to change sin core temp than skin temp

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29
Q

What do skeletal muscle effectors do?

A
  • Generate heat by shivering
  • involuntary cycle of contraction and relaxation
  • Only produces heat
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30
Q

What do endocrine gland effectors do?

A
  • increases metabolism to increase heat production
  • Releases thyroxine and catecholamines to cool the body
  • hormonal stimulation of heat production
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31
Q

Affects exercising in the heat has on cardiovascular system

A
  • ^ blood flow compared to cold
  • ^ cardiac output and ^ vasoconstriction to non essential tissues
  • decrease blood volume (sweat), ^ HR to compensate for cardiovascular drift
32
Q

Limitations of cardiovascular system when exercising in the heat

A

Cardiovascular overload
- heart cannot provide sufficient blood flow to both exercising muscle and skin
- impairs performance ^ overheating
- Especially affects untrained/ nonacclimated athletes

33
Q

Limitation: what is critical temperature theory?

A

when the brain shuts down exercise at 40-41 degrees

34
Q

Effect on body from dehydration

A
  • reduction of sweat (^ body heat storage)
  • ^ HR
  • small reduction in blood volume and pressure
  • large reduction in SV
  • reduced blood flow to active and inactive muscles, skin and brain
35
Q

Ways to artificially lower core temp (pre-cooling)

A
  • cold water immersion
  • cold room or shower
  • cooling vest
  • icy drinks
36
Q

What type of exercise benefits the most from precooling?

A

endurance events (may be detrimental for sprint events)

37
Q

What is sweating?

A

hot environmental temp > skin, core temps

38
Q

Sweat contents

A

Some Na and Cl absorbed
- light sweating: diluted
- heavy: less dilute (more Na, Cl loss)

39
Q

Sweat composition during training

A
  • more sensitive to aldosterone
  • more Na, Cl reabsorbed
40
Q

How much sweat loss during exercise?

A
  • Possible hourly loss of 1.6 - 2.0L
  • sweating decreases BV and card output
41
Q

What is fluid balance during exercise controlled by?

A

Hormones

42
Q

What does water loss trigger in the body?

A

Loss of water, electrolytes trigger release of aldosterone and antidiuretic hormone (ADH)

43
Q

What does aldosterone do?

A

retains Na at kidneys

44
Q

What does ADH do?

A

retains water at the kidneys

45
Q

6 factors of exercising in heat that may cause health risks

A
  1. Metabolic heat production
  2. air temperature
  3. humidity
  4. air velocity
  5. radiant heat sources
  6. clothing
46
Q

What are heat cramps?

A
  • least serious health risk
  • severe, painful cramping in large muscles
  • most common in heavy sweaters
47
Q

What is heat exhaustion

A
  • accompanied by fatigue, dizziness, nausea, vomiting, fainting, weak rapid pulse
  • simultaneous blood flow needs of muscle and skin are not met due to low blood volume
  • thermoregulatory mechanisms functional but overwhelmed
48
Q

What is the cause of heat cramps?

A
  • triggered by Na loss (dehydration)
49
Q

How are heat cramps prevented?

A

intake of Na, water

50
Q

What is heat exhaustion caused by?

A

Severe dehydration from sweating

51
Q

What is heat stroke?

A
  • life threatening and the most dangerous health risk
  • thermoregulatory mechanisms fail
  • confusion, disorientation and unconsciousness can occur
52
Q

Cause of heat stroke?

A

core temperature > 40 degrees

53
Q

How can this be treated?

A

Whole-body cooling ASAP (ice bath)
- if untreated may cause a coma or death

54
Q

How to avoid hyperthermia?

A
  • avoid outdoor activities when weather is > 28 degrees
  • practice early morning or evening
  • never restrict fluid intake (drink every 15-30 min)
  • Minimize clothing
55
Q

Practice guidelines in the heat

A
  • avoid practicing in > 28 degrees
  • keep adequate supply of fluids
  • customize fluid inake based on losses (1 L sweat = 1 kg weight loss)
  • aware of heat illness signs
  • organizers get final say to end events
56
Q

Positives of exercising in heat

A
  • rapid changes for better performance in hot conditions
57
Q

Effects acclimation has on heat exercise

A
  • optimizes cardiovascular function
  • changes sweating rate, sweat distribution, and sweat content
  • lower core temperature
58
Q

Differences women have exercising in heat

A
  • lower sweat rates than men
  • women have more active sweat glands but less sweat production per gland
59
Q

What happens to body when exercising in cold?

A
  • comes from any environment condition that causes loss of heat decreasing core/skin temperature
60
Q

What does POAH do when core temp decreases?

A
  • triggers peripheral vasoconstriction
  • triggers nonshivering thermogenisis
  • triggers skeletal muscle shivering
61
Q

What does the cerebral cortex do when core temp decreases?

A

triggers behavioural adaptations

62
Q

What is cold habituation?

A

After repeated exposures with no significant heat loss, shivering is blunted and core temp decreases

63
Q

What is metabolic acclimation?

A

After repeated exposures with heat loss, enhanced metabolic, shivering heat production

64
Q

What is insulative acclimation?

A

When ^ metabolism cannot prevent heat loss, enhance skin VC (^ peripheral tissue insulation)

65
Q

What is a factor that along with air temp, affects heat loss

A

windchill and cold water

66
Q

What happens to muscles when exercising in the cold?

A
  • function decreases
  • altered fiber recruitment decreases contractile force
67
Q

What is hypothermia?

A
  • Core temp is 34.5 - 29.9 degrees C: POAH function compromised
  • Core temp < 29.9: POAH thermoregulation completely lost, metabolism slows, drowsy, possible coma
68
Q

How is cardiorespiratory effected by cold?

A
  • HR slows
  • cold air does not damage ventilatory tissues
  • cold may decrease ventilation (rate and volume)
69
Q

Treatment for mild hypothermia

A
  • remove individuals from cold
  • Provide dry clothing, blankets and warm beverages
70
Q

Treatment for severe hypothermia

A
  • Handle gently to avoid arrhythmIAS
  • Rewarm gradually
  • may require hospital facilities, medical care
71
Q

What is frostbite?

A

Peripheral tissue freezing

72
Q

What happens if frostbite is untreated?

A

Loss of tissue

73
Q

How to treat frostbite

A

Gradually rewarm only when there is no risk of refreezing

74
Q

What is exercise-induced asthma?

A

Involves excessive airway drying affecting over 50% of winter-sport athletes

75
Q

How can exercise-induced asthma be treated?

A

B-agonists and steroid inhalers

Exercise Physiology (11 decks)

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