Heat

Question 1

Who does heat affect the most

Answer 1

Military
Athletes
Heat waves

Question 2

Heat and athletes

Answer 2

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

Question 3

Shape of our body and heat

Answer 3

Designed to move efficiently (slowly) and dump heat

Question 4

How to quantify internal severity of stress

Answer 4

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

Question 5

How to quantify external severity of stress

Answer 5

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

Question 6

Implications of heat balance equation

Answer 6

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

Question 7

Sensible heat loss (dry)

Answer 7

Dominates in cold environment

Question 8

Insensible heat loss (wet)

Answer 8

Dominates if temperature increases from exercise intensity

Question 9

Core temperature response to exercise

Answer 9

Increases as a function of the metabolic rate
Increases almost immediately

Question 10

What happens when core temperature rises

Answer 10

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

Question 11

What happens to heat dissipation as exercise continues

Answer 11

Heat dissipation balances heat production or heat intolerance ensues

Question 12

Exercise training in a temperature climate

Answer 12

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

Question 13

Exercise training in a hot climate

Answer 13

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

Question 14

Biological adjustments are mediated by

Answer 14

integrated changes in thermoregulatory control
Fluid balance
Cardiovascular responses

Question 15

Sweating power variability

Answer 15

Forehead and dorsal hands > torso and arms > lower limbs

Question 16

Can sweating power increase?

Answer 16

Yes, can double sweating power with training and heat acclimation

Question 17

Magnitude of biologic adaptations induced by heat acclimatization depends on

Answer 17

Intensity
Duration
Frequency
Number

Question 18

Heat acclimatization up keep

Answer 18

Transient and gradually disappears if not maintained by repeated heat exposure

Question 19

Types of heat illness in order of severity

Answer 19

Heat exhaustion
Heat injury
Heat stroke

Question 20

Heat exhaustion

Answer 20

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

Question 21

Heat injury

Answer 21

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

Question 22

Heat stroke

Answer 22

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

Question 23

Cardiac output equation

Answer 23

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

Question 24

Mean arterial pressure equation

Answer 24

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

Question 25

Describe peripheral vasodilation during heat stress

Answer 25

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

Question 26

Frank-sterling relation in heat stress

Answer 26

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

Question 27

What happens during heat stress

Answer 27

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

Question 28

Most effective cooling techniques

Answer 28

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

Question 29

Other cooling techniques

Answer 29

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

Question 30

Is face best place to apply cooling?

Answer 30

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

Question 31

What does precooling do

Answer 31

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

Question 32

Main factors governing performance in the heat

Answer 32

Aerobic fitness Acclimation or acclimatization Hydration Thermal status CHO availability

Question 33

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

Answer 33

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

Question 34

How can thermoregulation be impaired?

Answer 34

Spinal cord injury, babies and elderly

Question 35

Spinal cord injury thermoregulation impairment

Answer 35

Many afferent and efferent functions impaired

Question 36

Baby thermoregulation impairment

Answer 36

Increase area:mass ratio Increased head area Decreased behaviour

Question 37

Elderly thermoregulation impairment

Answer 37

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

Question 38

Athlete considerations during heat

Answer 38

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

Question 39

Para-athletes - Spinal cord injury

Answer 39

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)

Question 40

Para-athletes - cerebral palsy

Answer 40

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

Question 41

Para-athletes - multiple sclerosis

Answer 41

Heat intolerance/sensitivity due to demyelination of conduction pathways within the CNS Impaired sensory and effector responses

Question 42

Para-athletes - amputation

Answer 42

- 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

Question 43

Para-athletes - visual impairment

Answer 43

Unable to rely on visual feedback and cues to adapt pacing Unable to self-check hydration status via urine volume and colour

Question 44

Controlled _____ and ______ is good

Answer 44

Heat and shear stress (blood flow)

Question 45

How to attenuate age-related declines in function

Answer 45

Establish good heat therapy habits