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Terms in this set (196)
Why is body core temperature critical?
Because cellular structures and metabolic pathways are affected by temperature. Small range
What is a normal core temp? What too high of a core temperature and what is too low?
- Normal core temp is approx 37 degrees C
- >45 degrees C
- <34 degrees C
An increase in body temperature above 45 degrees C can do what?
- It can destroy the normal protein structure of enzymes resulting in death
What happens with the muscular contractile proteins when body temperature goes above 45 degrees C?
- muscular contractile proteins will start to break down, enter blood stream, go to the kidneys where filtering happens. The kidneys filter out the proteins so kidneys become damaged from having to filter proteins.
- Kidney damage/failure is why the person dies
A decrease in body temp below 34 degrees C can do what?
It can cause slowed metabolism and abnormal cardiac function (arrythmias) that can lead to death (heart attack).
Why is slowed down metabolism bad?
If slow down metabolism too much you can't make enough ATP for needs of the body.
Animals that maintain a rather constant body core temperature
Maintenance of constant body temperature requires what?
Requires that heat loss match the rate of heat production.
What do you do if someone has a heat stroke?
Put them in a tub of ice and water (careful to not bring body temp down to an extreme)
Homeotherms serve as a "furnace" rather than "refrigerator"
Our body temperatures are set at the high end of normal, we are losing heat continually but our bodies are always producing heat too. (continuous metabolic heat production)
Regulation by heat conservation or cooling capacity is more efficient?
Regulation by heat conservation and generation is very efficient, cooling capacity is more limited
What is the largest producer of heat in our bodies?
Contracting skeletal muscles
What type of exercise presents serious challenge to temperature homeostasis?
Long term exercise in hot/humid environment
What might be the only serious threat that exercise presents healthy people?
What individuals are more likely to die from heat stroke?
The young and old because both are less efficient so they will produce more heat per given amount of work
(also don't sweat as much)
What would you do to help keep the young and old safer in heat?
Replenishing water, time in shade
What is the goal of temperature regulation?
Maintain a constant core temperature and prevent heating or overcooling
(heat loss must match heat gain)
If heat loss is less than heat production, what happens?
There is a net gain in body heat and therefore body temperature rises
If heat loss exceeds heat production, what happens?
There is a net loss in body heat and body temperature decreases
During exercise, body temperature is regulated by what?
Adjustments to the amount of heat lost
What is the main system through which we lose heat?
Circulatory system- important function is to transport heat
What does blood have a high capacity for?
Blood has a high capacity for storing heat, which makes blood a good way to keep heat or get rid of heat
If we want to lose heat, what do our bodies do?
blood flow is increased to the skin as a means of promoting heat loss to the environment
- we vasodilate the blood vessels by our skin bringing the warm blood to the skin and get rid of heat
If we want to prevent heat loss, what do our bodies do?
Blood is directed away from the skin and toward the interior of the body to prevent additional heat loss.
- we vasoconstrict which will bring blood internally to increase body temperature
Within the body, temperature varies.
- There is a gradient between the core temperature (deep central areas like heart, lungs, abdominal organs), and the "shell" (skin) temperature
In extreme circumstances (extreme cold) the core temperature can differ from the skin temperature by how much?
The core temperature may be 20 degrees C higher than the shell. RARE
What is the ideal difference between core and shell temperatures?
Approximately 4 degrees C
Measurements of deep-body temperatures can be accomplished with many devices, such as?
- mercury thermometers
- Thermocouples or themistors
- Ingestible core temperature pills
In lab settings, what is a common site of core temperature?
- not the same as temperature in the brain where temp is regulated
- used to estimate changes in deep-body temperature during exercise
- used most frequently with exercise studies
- temperature measurements near the eardrum
- Good estimate of actual brain temperature
- measures core temperature (deep-body temp)
- not identical to brain temperature (like rectum)
Which three measurements of temperature are easily performed in lab settings?
*Limitations in field settings
What temperature sensor is used onfield and during practice sessions?
Ingestible temperature sensor telemetry system
How does the Ingestible temperature sensor telemetry system work?
Uses low-power radio frequency transmissions to communicate with a temperature monitor
- Can be measured by placing temperature sensors (thermistors) on skin at 7 various locations
What are the 7 various locations that skin temp is taken?
How do you calculate the mean skin temperature?
Take the average of those 7 locations and divide by 7.
Where is our temperature control center located?
How do we voluntarily increase heat production?
How do you involuntarily increase heat production?
Shivering and hormones that will increase metabolic rate
What happens with heat production at rest and when sleeping? When doing intense exercise?
At rest and when sleeping: heat production is small
Intense exercise: heat production is large
Heat production can be classified as either? (2 things)
1. Voluntary (exercise)
2. Involuntary (shivering or biochemical heat production caused by the secretion of hormones such as thyroxine and catecholamines)
How efficient is the body? How much energy do we lose as heat?
The body is 20-30% efficient, therefore 70-80% of the energy expenditure becomes heat
What is the primary means of increasing heat production during exposure to cold?
Shivering - maximal shivering can increase body's heat production five times the resting value
What are the two hormones that help to increase heat production?
- Released from thyroid
- Increases metabolic rate of all the cells in your body
Epinephrine and norepinephrine
Increases rate of cellular metabolism
This increase in heat production due to the combined influences of thyroxine and catecholamines is called what?
Heat loss from body may occur by four processes, what are they?
Radiation, conduction, and convection require what?
A temperature gradient between skin and the environment
- Transfer of heat via infrared rays
- Transfer of heat from the surface of one object to the surface of another with no physical contact made
Example of radiation?
Sun transferring heat to the earth via radiation
At rest in a comfortable environment (21 degrees C), how much of heat loss occurs via radiation? (body temp is 37)
How is this possible?
Because the skin temperature is greater than the temperature of surrounding objects (walls, floors) and a net loss of heat occurs due to the thermal gradient.
How can the body also gain heat from radiation?
On hot, sunny days when surface temperatures are greater than skin temperatures
Radiation can result in both what?
Heat loss and heat gain depending on environmental conditions
Transfer of heat from the body into the molecules of cooler objects in contact with its surface
How much heat is lost through conduction?
Example of conduction
If sitting on a block of ice, your body temperature will decrease because your heat is transferred into that block of ice
A form of conductive heat loss in which heat is transmitted to either air or water molecules in contact with the body
What happens to the air or water molecules in contact with the body?
The air and water molecules are warmed and move away from the source of heat and are replaced by cooler molecules.
How can you speed up convection?
Turn on fan or air conditioner
- a fan would increase the number of air molecules coming in contact with the skin and promote heat loss
Room temperature is 72 degrees and body is 98.6 so what is always happening?
We are continually heating up air molecules in contact with skin
Is water or air more conductive?
Water is more conductive so sitting in 72 degree water would result in greater heat loss than sitting in 72 degree air.
(water is 25 times more effective than air)
Would cycling at a fast or slow speed improve conductive cooling?
Fast because air going past you more quickly so air being heated up can pass by more quickly. Get rid of more heat
Heat is transferred for the body to water on the surface of the skin
Evaporation accounts for how much of heat loss at rest?
What is the most important means of heat loss during exercise?
When does vapor pressure occur?
Due to a vapor pressure gradient between the skin and the air
What is vapor pressure?
The pressure exerted by water molecules that have been converted to gas (water vapor)
Evaporative cooling during exercise exists in the following way:
- When body temp rises above normal, the nervous system stimulates sweat glands to secrete sweat onto the surface of the skin.
- The water on the skin is converted to water vapor that takes heat away (has to be a vapor to evaporate)
- As sweat evaporates heat is lost to the environment, which in turns lowers skin temperature
If you are just sweating are you always losing heat?
No, only the sweat that is evaporated with decrease your body temperature
If exercising in 105 degrees summer time, relative humidity is low, what will happen with sweat? Wonder if relative humidity is high?
- If relative humidity is low- sweat will be evaporated so won't feel like you are sweating but will feel salt on you
- If relative humidity is high- sweat won't be evaporated and wont be able to cool down as much.
Evaporation depends on what 3 things?
1. Temperature & relative humidity
2. Convective currents around the body
3. Amount of skin surface exposed
At high environmental temperatures, what is the most important factor influencing the rate of evaporative heat loss?
High relative humidity reduces what? What about when it is near 100%
High relative humidity reduces the rate of evaporation, when it is near 100% evaporation is limited.
Under what conditions is cooling by evaporation most effective?
Under conditions of low humidity.
The act of sweating does not transfer heat away from body, water has to _____?
Why does high relative humidity reduce rate of evaporation?
- High relative humidity (RH) reduces the vapor pressure gradient between the skin and the environment
- On hot/humid day (RH=80-90%) the vapor pressure in the air is close to the vapor pressure on moist skin therefore the rate of evaporation is greatly reduced
- High sweat rates during exercise in a hot/high humidity enviornemnt result in useless water loss (sweating per se does not cool the skin; it is evaporation that cools the skin)
What needs to be the case in order for evaporative cooling to occur during exercise?
Evaporation occurs due to a vapor pressure gradient- for evaporative coolig to occur during exercise, the vapor pressure on the skin must be greater than the vapor pressure in the air (the larger the vapor pressure gradient the more evaporation)
Vapor pressure is influenced by what 2 things?
Temperature and relative humidity
At any given temperature, a rise in RH results in increased _________
Less evaporative cooling occurs during exercise on a ______ day compared to a _______ day
- hot and humid
- cool/low humidity
Large skin-to-air vapor pressure gradient would permit relatively large evaporative rate, therefore body cooling would occur under these conditions.
How much heat can be lost via evaporation during exercise?
The body loses .58 kcal of heat for each ml of water that evaporates. Therefore, evaporation of 1 liter of sweat would result in a heat loss of 580 kcals (1,000 x 0.58 kcal/ml = 580 kcal).
What sports would have a large amount of evaporative heat?
Cross Country Skiing because a large amount of skin exposed
What type of job would result in reduced evaporative heat?
Where is heat produced that is not lost stored?
In the body tissues
What will stored heat do?
Raise body temperature
The amount of heat gain in the body during exercise is computed as what?
The amount of heat gain in the body during exercise is computed as the difference between heat production and heat loss
Body heat gain during exercise = (Heat produced-heat lost)
The amount of heat energy required to raise the body temperature depends on what?
The amount of heat energy required to raise body temperature depends upon the size of the individual (weight) and a characteristic of body tissue called specific heat
Amount of heat required to raise 1 kg of body tissue by 1 degree C
Specific heat for human body
0.83 kcal/kg of body mass
Equation for heat required to increase body temp by 1 degree C?
Heat required to increase body temp by 1 degree C = (specific heat x body mass)
Ex. 0.83 x 70 kg = 58.1 kcals
1 L of sweat results in heat loss of ____ kcals
During exercise in a cool environment, ____ is the primary avenue for heat loss
What conditions is cooling by evaporation most effective?
Cool and dry
Body's temperature regulatory center
Primarily responsible for dealing with increases in body heat
Primarily responsible for reacting to a decrease in body temp.
Hypothalamus operates to do what?
To maintain a relatively constant core temperature around some "set point"
Set Point in humans
37 degrees C
Where does the input to the temperature regulating centers in the hypothalamus come from?
Receptors in both the skin and the core
What are changes in the environmental temperature first detected by?
Thermal receptors (both heat and cold) located in the skin
What do this skin temperature receptors then do?
Transmit nerve impulses to the hypothalamus, which then initiates the appropriate response in an effort to maintain the body's set-point temperature.
Where are the heat-cold sensitive neurons located?
Located in both the spinal cord and the hypothalamus itself, sensing changes in the core temperature.
If body temperature increases, what is the response?
The anterior hypothalamus
- if body temperature increases, start sweating to increase evaporative loss
- Increase blood flow to the skin by vasodilating, therefore the heat from the blood is close to the kin and can be discipated into environment via convection, radiation, etc.
When core temperature returns to normal, what happens?
The stimulus to promote both sweating and vasodilating is removed.
What is anterior hypothalamus an example of when body temp increases?
When there is a decrease in core temperature, what is the response?
- increase in the catecholamines and thyroxine which help to vasoconstrict (reduce heat loss), therefore increasing the metabolic rate so having greater heat production
- decrease in amount of blood going to skin
Calculation of heat loss via evaporation
- 20 minutes cycling at VO2 = 2.0 L min
- 20% efficient = 80% energy lost as heat
Total energy expenditure in kcals?
Total heat produced in kcals?
Evaporation to prevent heat gain?
Evaporation of 1,000 ml of sweat results in 580 kcal of heat loss
Total energy expenditure:
20 min x 10 kcal/min = 200 kcals
Total heat produced in kcals
200 kcal x .80 = 160 kcal
Evaporation to prevent heat gain
160 kcal/580 kcal/L = .276 L
Calculation of Body Temperature Increase During Exercise
(60 kg runner, 40 min at VO2= 3.0L/min (15kcal/min) 20% efficient, can lose 60% of heat produced, pre-exercise body temp = 37 degrees C)
Total energy expenditure?
Total heat produced?
Total heat stored?
Amount of heat storage to increase body temp by 1 degree C?
Increase in body temp during exercise?
Post-exercise body temp?
Total energy expenditure:
40 min x 15 kcal/min = 600 kcal
Total heat produced?
600 kcal x .80 = 480 kcal
Total heat stored?
480 kcal x .40 = 192 kcal
Amount of heat storage to increase body temp by 1 degree C?
.83 kcal/kg x 60 kg = 49.8 kcals
Increase in body temp during exercise?
192 kcal/49.8 kcal/degree C = 3.86 degree C
Post-exercise body temp?
37 degree C + 3.86 degree C = 40.86 degrees C
A fever is an increase in a body temperature above the normal range that may be caused by numerous bacterial/viral infections or brain disorders.
Why is there a shift in the Hypothalamic Thermostat Set Point Due to Fever
During fever, select proteins and other toxins secreted by bacteria can cause the set point of the hypothalamic thermostat to rise above the normal level.
What are the substances that cause this shift called?
Submaximal constant-load exercise in cool enviornment results in 3 things:
1. Heat production increases
2. Nervous system response
3. New Steady state core temperature
Heat production increases during exercise due to muscular contraction and is directly proportional to _____
What distributes the excess heat throughout the body core?
Venous blood draining the exercising muscle distributes the excess heat throughout the body core.
What happens as core temp increases?
thermal sensors in the hypothalamus sense the increase in blood temp and the thermal integration center in the hypothalamus compares this increase in temp with the set points temp and finds the difference between the two.
This response is to direct what?
The nervous system to commence sweating and to increase blood flow to the skin (vasodilate)
These acts serve to increase body heat loss and minimize increase in body temperature. What happens to the internal temp at this point?
- At this point, the internal temp reaches a new elevated steady state level (but this does not represent a change in the set point temp as occurs with fever)
- Instead, the thermal regulatory center attempts to return the core temp back to resting levels, but is incapable of doing so bc of continual contraction of muscle during exercise.
What roles do convection, radiation and evaporation play during this type of exercise? (submaximal constant-load exercise in cool environment)
- There is a constant but small role of convection and radiation in heat loss during this type of exercise due to a constant temperature gradient between the skin and the room
- In contrast, evaporation plays the most important role in heat loss during exercise in this type of environment
During constant load exercise, core temp incrase is directly related to the ______ and is independent of _________ over a wide range of conditions.
As exercise intensity increases, you see an increase in body temp in both ____ & _____
Arms and leg exercises
The fact that it is the exercise intensity and not environmental temp that determines rise in core temp during exercise suggests that the method of heat loss during continuous exercise is modified according to ambient conditions
- As ambient temp increases, the rate of convective and radiative heat loss decreases due a decrease in the skin-to-room temp gradient.
- This decrease in radiative and convective heat loss is matched with an incrase in evaporative heat loss and core temp remains the same
There is a linear increase in ___ & ____ & _____ as a function of exercise intensity
energy expenditure, heat production, and total heat loss
What forms of heat loss do not increase as a function of exercise intensity? What is there an increase in as a function of exercise intensity?
- Convective and radiative heat loss are not increased as a function of exercise work rate due to a relatively constant temperature gradient between skin and environment.
- BUT there is a consistent rise in evaporative heat loss with increments of exercise intensity
As ambient temperature increases, what happens?
- convective and radiant heat loss DECREASE
- evaporative heat loss INCREASES
Measure of body's perception of how hot it feels when relative humidity is added to the actual air temp
What is the heat index measured in?
How is heat index calculated?
By combining air temp and relative humidity to compute an apparent temperature
What happens in terms of heat index when relative humidity is high?
- When relative humidity is high (high water vapor saturation in atmosphere), the evaporation of sweat is retarded; heat removed from the body at a lower rate resulting body heat storage and increase in body temp.
- Thus, high humidity increases an individuals perception of how hot the environment feels.
Higher the humidity, the less _____
Less heat removed, _____ will increase
body's core temperature
High heat and humidity reduce the body's ability to lose heat by what?
radiation/convection and evaporation
• The combined effect of fluid loss and high core temperature increases the risk of hyperthermia (large rise in core temp)
What does this inability to lose heat during exercise result in?
- A greater core temperature
- A higher sweat rate (more fluid loss) --> risk of hyperthermia and heat injury
Higher sweat rate?
May be as high as 4-5 L/hour
Risk of dehydration
In cool environment, what happens to sweat rate and body temperature?
Sweat rate is relatively low
Body temperature increases then plateaus
In hot environment, what happens to sweat rate and body temperature?
Sweat rate increases
Body temperature continually increases
Heat accustomed individuals in terms of sweating?
Have an earlier onset of sweating a higher sweat rate during exercise
Large individuals in terms of sweating?
will likely have higher sweat rates compared to smaller individuals.
Genetic variations with sweating
Genetic variations in sweat rates exist such that two individuals with the same body size and level of heat adaptation may also differ in sweat rates.
How much dehydration can impair performance?
Dehydration of 1-2% body weight can impair performance
What are guidelines to prevent dehydration during exercise?
- hydrate prior to performance (400-800 ml) 2-3 hours before
- Consume 150-300 ml of fluid every 15-20 mins
- Ensure adequate rehydration
- Monitor urine color
What type of drink is superior to water for rehydration?
Sports drinks (flavor)
What % decrease in body weight can impair physiological functioning and increase chance of heat injury
If it is a hot humid day, how much fluid do you want to take in and every how many minutes?
300 ml of fluid every 15-20 minutes
If it is a cool day, how many ml of fluid do you need?
Need to be consuming ___% of what you lose
150% or 1.5 L
want light yellow vs. dark yellow
Rust color is bad
What is hyperthermia
rise in core body temp
How is exercise performance impaired in a hot environment?
- Exercise in heat accelerates muscle fatigue
- Accelerated glycogen metabolism
- Increases free radical production
- Reduced muscle blood flow
- Higher brain temperature reduces neuromuscular drive
What two types of exercise are impaired in hot/humid environment?
Prolonged exercise (marathon) and intermittent (soccer)
Why does an increase in the rate of muscle glycogen depletion cause an impaired performance?
- During exercise in the heat, rate of muscle glycogen degradation is increased with a parallel rise in both carbohydrate metabolism and lactate accumulation
Why is this important?
- This is important because muscle glycogen depletion and low blood glucose levels (hypoglycemia) are associated with muscle fatigue during prolonged exercise
What else is associated with muscle fatigue?
Exercise-induced increases in muscle pH are also linked to muscle fatigue
Therefore overall depletion of muscle glycogen stores and high lactate levels could contribute to what?
muscle fatigue during prolonged exercise in the heat.
What are free radicals?
- Free radicals are molecules with an unpaired electron in their outer orbital
- Molecules with an unpaired electron are highly reactive
Free radical production is increased in skeletal muscles during exercise in the heat, why could this impair performance?
- Free radicals bind quickly with other molecules and this combo results in damage to the molecule combining with the radical
- Therefore, accelerated production of free radicals during exercise in the heat could contribute to muscle fatigue because of damage to muscle contractile proteins.
Heat stress can result in cardiovascular strain and reduced muscle blood flow, why can this impair performance?
- Reduced muscle blood flow doesn't contribute to poor exercise tolerance during light or moderate exercise bc muscle blood flow is well maintained under this exercise conditions when dehydration does not occur.
- During high intensity exercise performed in hot/humid environment, there is a progressive decline in muscle blood flow due to a competition for blood between the working muscles and the skin.
What happens as body temperature rises during exercise in a hot environment?
Blood flow moves away from the contracting muscle toward the skin to assist in cooling the body
During high intensity exercise, can reduced muscle blood flow contribute to impaired performance? What can it not explain?
- During high intensity exercise, reduced muscle blood flow can contribute to impaired exercise performance in the heat
- In contrast, reduced muscle blood flow cannot explain the heat-induced reduction in exercise performance during light to moderate intensity work
Both hyperthermia and dehydration can directly diminish exercise performance due?
central nervous system impairment because higher brain temperature.
- Reduces the neuromuscular drive for motor performance
- reduction in motor unit recruitment
Overall, heat induced fatigue is not due to a single factor but probably results from a combo of what metabolic events?
Alterations in muscle metabolism, impaired cardiovascular function/fluid balance, and CNS dysfunction resulting in impaired neuromuscular function
Strategies to improve exercise tolerance in hot environment?
Become heat acclimated and consume fluid before and during exercise
Are there gender differences in heat tolerance (thermoregulation)?
- Previously thought women were less tolerant of exercise in hot environment
- NOW, shown that there are only small differences in heat tolerance
Age itself doesn't limit ability to thermoregulate, what does?
- deconditioning with age
- lack of heat acclimatization
Rapid adaptation (days to week) to environmental change
Adaptation that occurs over a long time period (many week to several months)
Results of acclimation?
- Lower heart rate
- Lower core temperature during submax exercise
Partial heat acclimation occurs by what?
Maximal heat acclimation occurs by what?
- Partial heat acclimation occurs by training in cool environment, BUT training in hot environment will obtain maximal heat acclimation
What is the primary stimulus to promote heat acclimation?
Because an elevation in core temperature is the primary stimulus to promote heat acclimation, its recommended that the athlete perform strenuous interval training or continuous exercise at an intensity exceeding 50% of their VO2 max in order ot promote higher core temperatures
Therefore, acclimation requires that you work out in what type of environment to see elevated core temperatures that promote adaptations?
When is complete acclimation achieved by?
Almost complete acclimation being achieved by 7-14 days after the first exposure
How long does it take to lose heat acclimation?
Heat tolerance will be lost within 7 days of not being in the heat, after 28 days you've completely lost all you've gained with heat acclimation.
The primary adaptations that occur during heat acclimation:
- 10-12% Increased plasma volume
- Earlier onset of sweating
- Higher sweat rate
- Reduced salt loss (sodium cholride) in sweat
- Reduced skin blood flow
- Increased synthesis of heat shock proteins
Increase in plasma volume leads to
maintain blood volume, stroke volume, ability to sweat is increased so smaller gain in temp
Earlier onset of sweating
- Start exercising and sweat right away even if body temp hasn't gone up
- Sweat more
- Storing less heat and therefore core temp won't increase as much
Higher sweat rate
- More ability for evaporation to happen
- 3 fold increase in ability to sweat
Reduced sodium chloride loss in sweat
- Lose less sodium which is beneficial because the more water in sweat the easier it is to evaporate
Reduced skin blood flow
More blood going to the working muscles
Increase in cellular heat shock proteins
Prevents cellular damage from heat
Number of days required for heat acclimation?
In 3 days ill see changes:
- HR decrease
- Plasma volume increase
In 5 days:
- perceived exertion ... feel less challenging
In 8 days:
- sweat rate increases
Exercise in a cold environment enhances what?
An athletes ability to lose heat and therefore greatly reduces the chance of heat injury (enhanced heat loss)
What can exercise in cold environment result in? How can you prevent this?
- The combination of metabolic heat production and warm clothing prevents the development of hypothermia (large decrease in core temp) during short term work on a cold day
Individuals with a high % of what improves cold tolerance?
- Individuals with high % of body fat have advantage over lean individuals when it comes to cold tolerance
- Large amount of subcutaneous fat provide an increased layer of insulation from the cold
What does this increased insulation reduce?
the rate of heat loss and improves cold tolerance
Do men or women generally tolerate mild cold exposure better?
Other problems associated with sports in the cold
- Hands become numb due to reduction in the rate of neural transmission and reduced blood flow due to vasoconstriction
- This results in loss of dexterity and affects throwing and catching
- Frostbite- serious medical condition
What is the ideal temp for marathon runners?
If elite runner running on 70 degree day vs. 50, by what % will their time be slower?
None elite runners will have an decrease in time by what % because why?
12% because decrease in heat production (running in groups and running in sun longer)
3 major physiological adaptations occur when humans are chronically exposed to cold temperatures
1. Reduction in the mean skin temperature at which shivering begins
2. Maintain a higher mean hand and foot temperature during cold exposure
3. Improved ability to sleep in cold environments
1. Reduction in the mean skin temperature at which shivering begins
- People who are cold acclimated begin shivering at a lower skin temp
- WHY? Cold acclimated people maintain heat production with less shivering by increasing nonshivering thermogenesis
How is this achieved?
This is achieved by increase in the release of norepinephrine, which results in an increase in metabolic heat production
2. Maintain a higher mean hand and foot temperature
Improved intermittent peripheral vasodilation to increase blood flow (and heat flow) to both the hands and feet
3. Improved ability to sleep in cold environments
- Unacclimated people shiver so much they cant sleep
- Acclimated people sleep comfortably due to elevated levels of nonshivering thermogenesis.
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