Exercise in hot and cold Flashcards
(89 cards)
1
Q
what is the importance of exercise in hot and cold
A
the body temp must be regualted in different external thermal conditions
2
Q
homethermic
A
- humans are this
- means internal body temp is nearly constantly regulated despite environmental temp changes
3
Q
what is normal core body temp
A
37 degree C
4
Q
thermoregulation
A
regulation of body temperautere around a physiological set point
5
Q
acclimation
A
short term adaptation to environment stressor
- occurs over days or weeks
6
Q
acclimitization
A
- long term adaptations to environmental stressor
- occurs over months and years
7
Q
what is metabolic heat production
A
the heat generated by the body as a byporduct of metabolic processes
8
Q
what is characterized by metabolic heat vs cellular wokr
A
- <25% ATP breakdown –> cellular work
- > 75% ATP breakdown –> metabolic heat is created
9
Q
what are the different modes of heat transfer
A
- conduction
- convection
- radiation
- evaporaton
10
Q
conduction
A
- K
- heat transfer from one solid materia to another through direct molecular contact
11
Q
convection
A
- C
- heat transfer by movement of gas or liquid across a surface
12
Q
what is a major thermoregulator factor and the most effective way of heat transfer
A
convection
- increased movement across the skin surface –> increases heat exchange
13
Q
radiation
A
- K
- heat loss in the form of infared rays
14
Q
evaporation
A
- E
- heat loss via phase exchange from liquid to gas
15
Q
what is evaporation affected by
A
humidity
- lower humidity –> increased E
- higher humidity –> lower E
16
Q
insulation
A
- I
- resistance to dry heat exhange
17
Q
what is insulation in terms of humans
A
- more fat/muscle = more insulation
18
Q
what is an ideal insulator
A
- still layer of air
- eg what is seen with wetsuits
19
Q
what temp could the body withstand with unlimitted C + E
A
200 degrees C
20
Q
what is a core temp range that the body can briefly withstand
A
<35 and >41
21
Q
what happens to the body if core temp is >40
A
- inhibits physiological funtion
- under prolonged conditions brain will be affected and can lead to heat stroke
22
Q
what happens when the core temp <35
A
- inhibits cognitive function
23
Q
what is thermoregulatory function controlled by
A
Preoptic-anterior hypothalamus (POAH)
24
Q
what is POAH
A
the bodys thermostate located in the brain
- recieves input from sensory thermoreceptors (skin, spinal cord) to ensure that cerebral spinal fluid doesnt get too hot
25
how is POAH activated in the heat
increased blood and internal temp --> increased temperature is sensed by the hypothalamus --> SNS activated --> 1. vasodilation in skin blood vessels 2. sweat glands become active increasing evaporative heat loss --> body temp decreases
26
what activates eccrine sweat glands
Ach sympathetic cholinergic stimulation = sweat
27
how does sweat change over time
- composition, distribution, and amount can change with prolonged exposure
- also different within each person
28
how is POAH activated in cold temps
decreased blood or skin temp --> decreased blood temp is sensed by POAH --> SNS acitvated --> 1. vasoconstriction occurs in skin blood vessels so less heat is lost to the environement (insulation) 2. skeletal muscles activated increasing shivering --> body temp increases
29
what are the two types of shivering
true shivering
high frequency shivering
30
true shivering
- low/moderate frequncy shivering of larger muslce groups
- burns a ton of energy
31
high frequency shivering
- not purely for heat production
- seen in extreme cold stress where smaller muslce groups shiver
32
which shivering is involuntary
- high frequency shivering
- reuslts in buzzing / vibration in muslces
33
how do endocrine glands effect body temp
- increased metabolism via epi = increased heat production
- cold body = release thyroxine + catecholamines
hormonal stimulation through T3 + T4 (more long term response)
34
what happens when you exercise in the heat
exercise --> increase M heat load --> disrupts thermal homestasis --> must regualte
35
what happens to CVD when exercising in the heat
- skin arterioles vasodilate --> increasing blood flow --> increasing convectional heat loss
- POAH triggers SNS --> increase CO --> increase further via HR/contractility --> increase VC to nonessential tissues
- blood volume decrease bc of dehydration --> decrease sweat --> SV cant increase --> blood pooling --> increase HR to further compensate = cardiovascular drift
36
cardiovascular drift
continual increase in HR over extended exercise even if no damage or change in activity
37
are the limitations of exercise in the heat
CVD overload and critical temperature theory
38
what is CVD overload in relation to limitations of exercise in the heat
- heart cant provide enough bloodflow to both exercising muscles and skin = impaired performance
- can lead to risk of overheating esp in environemnts that are humid/hot
39
where is CVD overload most commonly seen
with untrained or nonacclimated athletes
40
what is the critical temperature theory
brain shuts down exercise @ around 40-41 degrees
- used to explain limitations seen in trained and acclimated athletes
41
how does fluid balance work with exercise in the heat
regulation of sweat and electrolytes
42
how is sweat affected with exercise in the heat
- occurs when environment temp > skin core temps
- C, K, R --> heat gain --> E is the only avenue of heat loss
- can lose up to 1.6 -2.0 L each hour
- increased sweating --> decreased blood volume --> decrease cardiac output
43
body weight and sweating relationship
- fluid loss is about 2.5-3.2% of body weight
- more body weight = more fluid loss which is why larger atheletes should get a baseline weight
44
realtionship of sweat and electrolytes
- sweat electroluyte content < plasma bc ducts reabsorb some Na+ and Cl-
- w/ heavy sweating = plasma is less dilute and there is more Na+, Cl- loss
45
how does training affect sweat composition
a long term adapataion is seen where continued exposure to heat exercise = more sensitive to aldosterone = increased kidney effeciecnty = able to reabosrb more ions like Na+ and Cl- while keeping K+, Ca2+, and Mg2+ unchanged
46
what is the hormonal response to electrolute and body water loss
the decrease of water and electrolytes stimulates the release of aldosterone and ADH initiating RAS and Vasopressin response
47
what are health risks in heat exposure dependent on
- metabolic heat production
- air temperature
- ambient water vapor pressure
- air velocity
- radient heat sources
- clothing
48
how does metabolic heat affect health risks in the heat
greater intensity = greater metabolic activity
49
how does air temperature affect health risks
limits the amount of convection
- increased temp = less efficient convection
50
how does ambient water vaport pressure (humidity)
can cause less efficient cooling
51
how does air velocity affect health risks in the heat
strong wind in hot environments can offset the effects of high temp
52
how does radient heat sources affect health risks in the heat
paved vs. rubber. vs grass affect how temperature is radiated from the sun and can increase heat
53
what are the different issues that can arise from exercising in heat
heat cramps, heat exhaustion, heat stroke
54
what are heat cramps
- severe, painful cramping of large muscles
- triggered by Na+ loss, dehydration, causes inability to maintain RMP
55
how can heat cramps be prevented
liberal intake of Na+ water
56
what is heat exhaustion
- severe dehydration from sweating = simultaneous blood flow needs of the muscle and skin not met = heat gain faster than how much can let off
- nausea, vomiting, fainting weak + rapid pulse
57
during heat exhaustion what happens to the thermoregulatory mechanisms
they are functional but overwhelmed
58
what is heat stroke
- thermoregulatory mechanism failure when core temp > 40
- life threatening and the most dangerous condition
- confusion, disorientation, unconsciousness, cessation of sweating , and if left untreated can lead to coma and death
59
how to treat heat stroke
cool the whole body ASAP
60
how to prevent hyperthermia
no outdoor activities when the WBGT is >28 degrees
- schedule practice for early morning or evening
- never restric fluid intake ( drink breaks around 15-30 mins) this can help minimize rise in HR and core temp
- minimize clothing
61
how does fluid intake affect core temp during exercise in the heat
it allows for a slower increase a lower peak temp
62
how shoudl fluid intake be customized for athletes
1 L of sweat loss = 1 kg weight loss
63
what is the time frame of acclimation in the heat
9-14 days
64
what occurs for acclimation in the heat
- CVD function is optimized
- swerating rate, sweat distribution, and sweat content changes
- lower core temp during exercise
- plasma volume increase due to oncotic pressure
65
how is CVD function optimized when acclimated to exercise in the heat
- decreased HR for the same intensity
- increased cardiac output
- support os increased skin blood flow
- greater heat loss and lower core temp
66
how is sweating affected when acclimated to exercise in the heat
- widespread sweating occurs earlier = more dilute
- helps to prevent dangerous Na+ loss
- optimized E heat loss
67
what is cold stress
- any environmental condition causing loss of body heat
- causes a decrease in core or skin temp that triggers physiological + behavioral mechanisms
68
how is peripheral VC triggerd in response to the cold
- POAH triggers VC to brind blood back to core and stay warm
- organs and body undergoes an order of operations when VC occurs (will lose toes first)
69
how are organs affected when VC occurs
not affected that much since they are able to survive with decreased blood flow
70
cold habituation
occurs after repeated exposeres w/o significant heal loss
- VC + shivering is blunted and core temp is allowed to decreased more
71
what happens to sugar metabolism in the cold
- it increases esp during cold habitutaiton
- can lead to hypoglycemia
72
metabolic acclimation for exercise in the cold
- occurs after repeated cold exposure w/ heat loss
- enhanced metabolic mechanisms and shivering heat production
- increase in beta oxidation is seen
73
insulative acclimation
- when increalse in metabolism cant prevent heat loss
- enhanced skin VC acts as a thermal barrier to keep warmth @ muscles
74
what is a hypothermia inducing environment
- hard to say exact criteria but anyting that drops the core temp below 37 degrees will initiate a cold response
- also depends on person and body comp
- must consider windchill and other effects
75
how does cold response differ within each person
- greater peripheral muscle and subcutaneous fat = increase insulation
- women have more subcutaneous fat which is advantageous but also have less active muscle
- age: as you get older you lose more brown fat, and there is a decrease in SA:BM ratior
- race: some races hold more fat
76
how does windchill effect heat loss
- refers to the colling power of the environment
- increases C heat less
77
what are physiological responses to exercise in the cold
- decreased muscle function
- nonshivering thermogenesis + shivering = high demand of energy
- increase in fatigue = decrease in metabolic heat production
- change in FFA metabolic responses
- glucose metabolic response
78
how is muscle function affected during exercise in the cold
- theres altered fiber recruitment = decrease in contractile force
- decrease in shortening velocity + power bc od decreased sugar
- affects superficial muscles while deep muscles are spared
79
why doese metabolic heat production decrease with more fatigue when exercising in the cold
- energy depletion occurs w aerobic exericse = cause for hypothermia
- with a decrease in sugar fatigue occurs faster
- can combat by consuming more sugar and dressing warm
80
how is FFA metabolism affected in the cold
- catecholamin release occurs but no increase in FFA mobilization and oxidation
- due to VC in subcutaneous fat that decreases FFA mobilization to keep for insulation
81
what is the glucose metabolic response during cold
- blood glucose is well maintinged during cold exposure but muscle glycogen utilization increases
- when hypoglycemic in cold shivering sopts = decrease in heat production = decrease in core temp = hypothermia
82
heath risks when exericsing in the cold
hypothermia
- cardiorespiratory effects
frostbite
Exercise-induced asthma
83
hypothermia
When the core temp is around 34.5-29.5 degrees POAH function is compromised
- core temp < 29.5 POAH thermoregulation completely lost, metabolism slows, drowsiness, lethargy, coma
84
treatment for mild hypotehrmia
remove individual, provide blankets, clothing, warm beverages
85
treatment for severe hypothermia
gentle handling to avoid arythmia, gradual reqarming, may require hospital or medical care
86
what happens if you heat someone to fast
- can cause reprofusion injuries
- fresh blood hits cold tissues = increase ins stress bc of temp different = inability to VD
87
what are cardiorespiratory effects of cold
low core temp = slow HR bc it affects the SA node
- cold may decrease ventilation rate and volumes
88
frostibite
peripheral tissue freezing
- excess VC = lack of O2 and nutrients = tissue death
- untreated frostbite --> gangrene and tissue loss
89
what are some comparitave adaptations
- fur
- fat (location (fatty livers in animals, quantitiy, qualitity (brown fat))
- huddling and migration
- hibernation (seen a decrease in HF)
- torport
- metabolic changes
