Thermoregulation and hydration- EXPH 4189

What might've been the issue that triathlete experienced at the end of his race when he had an altered state and almost fell?

dehydration

heat stroke

humid environment

producing a ton of heat

genetics

not heat acclimated

Do lots of people walk around dehydrated?

Yes- some

How would you know they are dehydrated/what would you measure or look for?

thirst

body weight loss

concentrated urine

elevated resting HR

head rush

high levels of electroly

Consequence of inadequate hydration

low BP causing syncope

kidney stone

Lost more than 1% of body weight

Low Blood volume = _______ BP

low

Water balance

Need same amount of fluid added and lost

Water intake

beverages (most)

food

metabolic water

Water output

Urine- 60% of loss

Lungs

Evaporation thru skin/sweat loss

feces

How are you losing fluid thru lungs?

Anytime you are in a space breathing in dry air, you must humidify it through your lungs

*Equals metabolic water you make with intake**

Three locations for fluid

blood

interstitial space

cells

How does water flow between compartments?

By following electrolytes

Where is the majority of fluid?

2/3 is in cells

1/3...interstitial space (most here) and some in blood

Do males or females have more fluid? Why?

Males

leaner and lean tissue holds more fluid than fat tissue

If you drink water it is absorbed in the _______ and then distributed from there into _______ and _______

blood

interstitial space, cells

Water is removed from the blood by the _________ and excreted as _______

kidney

urine

Hyperhydration

too much water

Euhydration

normal hydration

Hypohydration

dehydration

Osmolarity

total concentration of all solute particles in a solution

Osmolarity of body vs. sweat

body- 300 mOsm

sweat- 100 mOsm

Control of hydration status is done by the ________ in the brain

hypothalamus

When osmolarity increases (too concentrated), the hypothalamus tells the pituitary to secrete _________ which preserves water in the kidneys making urine __________ __________. This process makes someone __________(more/less) thirsty

antidiuretic hormone

more concentrated

more

Homeotherm

constant body temperature

Normal core temp

97-100

Core temp

inside brain & torso

need tight regulation

Skin/shell temp

Can change it without having big impacts

Head added and heat loss from the system needs to be in ____________

balance

Heat gain mechanisms

metabolic heat

conduction

convection

radiation

Heat loss mechanisms

radiation

conduction

convection

evaporation

Conduction

The direct transfer of heat from one substance to another substance that it is touching.

Convection

air moving over your skin

Radiation

The transfer of energy by electromagnetic waves

Evaporation

The change of a substance from a liquid to a gas

CAN ONLY LOSE HEAT HERE NOT GAIN

Conduction- tile floor

Feeling heat leave your feet (sensation of being cold)

Not feeling the temperature of other tile

Temp always goes from ________ to _______

high to low

Why can you put a pan of cookies into the oven and not burn yourself, but you need an oven mitt to take them out?

In- air is not a good conductor of heat, so can touch the metal initially

Out- metal has a high conduction of heat so need an oven mitt to not burn yourself

maximal sweating rates

2-4 L/hour

1 L = ______ kg....what's the significance?

1 kg

means you are losing 2-4 kg which is 4-9 lb/hour = extreme

1 L = ______ kcal of heat

580 kcal

Salt = _____ g/L sweat

3 g/L of sweat

More loss here than the amount recommended by US dietary guidelines- 2.3 g/day

How does humidity impact evaporation?

If it's 100% humid you cannot evaporate sweat

Which becomes an issue for cooling yourself

Control system if you get too hot

Vasodilate to send blood to skin

Trying to balance heat added by evaporating more

Cannot control radiation because that's just the room temp

Control system if you get too cold

Prevent blood from going to skin, keeps in core, causes shivering

Burning ______ kcal/min at rest

1 kcal.min

Is all energy we produce lost as heat?

No

During exercise from rest to max in a normal environment, what are the typical energy trends?

UP- amount of energy burned

UP- amount of heat produced

UP- total heat loss

UP- evaporative heat loss

SAME- convective and radiative heat loss

Why does energy burned go up during exercise?

Because you increase your metabolism during progressively more intense exercise

The difference between heat burned and heat produced is _________________

Mechanical efficiency- which is the energy that actually went to power you during exercise

The difference between heat produced and heat loss is the ___________________

heat balance equation

Is the total heat loss MORE or LESS than the amount of heat produced?

LESS, so your core temp should be increase

Why doesn't convective or radiative heat loss go up?

Room temp didn't change during exercise

What is the MAIN mechanism we can rely on to cause heat LOSS?

evaporation

How do these energy trends CHANGE in HUMID/HOT environments?

DOWN- Total heat loss (because the sweat on your skin isn't able to evaporate much)

DOWN - Evaporation

UP- difference/gap between heat loss and heat production because you are moving toward heat exhaustion (producing SO much heat, but not able to lose it)

During exercise in a hot/humid environment, explain why the gap between heat production and heat loss will increase?

You are moving toward heat exhaustion- you will be producing MORE HEAT from exercise but won't be able to LOSE that heat due to the inability to allow sweat to evaporate off the skin

How do the energy trends change during exercise in a COLD environment?

Radiation loss will be higher

Total heat loss could move closer to heat production

Would sweat less

If you produce more heat than the amount of heat you lose, what happens to your core temp?

RAISES core temp

What happens to rectal temperature when exercising in a hot vs. normal environment?

Hot- Temp goes UP a TON

Normal- Temp goes up slightly due to exercise hyperthermia

How is SV impacted from exercising in a hot environment?

Stroke volume is LOWER due to vasodilation in the skin, so blood wants to hang out there

How does the body compensate for a lower SV in a hot environment?

INCREASE HR to maintain cardiac output

HR is ________ in a hotter environment

HIGHER

When you are exercising in a hot environment and begin to run into HR max, why is this an issue?

You can't compensate for low SV by boosting HR because you are at your HR max

How is cardiac output impacted by hot environments?

Cannot go to same high exercise intensity because you can't keep up cardiac output

What two things are competing for blood?

Active muscles (VO2)

Skin (dissipate heat)

Performance impairments start at ______% body weight loss

2%

Consequences of dehydration are on a __________. One thing leads to the next

continuum

heat exhaustion- how severe? what can we do? symptoms?

not extreme enough to go to the hospital

Need to stop them before they get too warm...can just put in shade, cool to drink

Symptoms= Sweating a lot, Nauseous, Light headed

heat stroke- how severe? what happens?

Life threatening

Damage to nervous system

Can no longer control things optimally

More confusion or loss of consciousness

Is the thirst mechanism precise enough according to the ACSM guidelines on fluid replacement?

No

You should be drinking _______% more than what you are losing, which is like ________ liters for each kg lost

50%

1.5 L

When you drink water what happens in the blood stream?

Adding lots of water to blood stream, which will quickly dilute blood, kidney will try to make a lot of urine from that

Why are electrolytes important for fluid replacement?

They match the osmolarity that you want

There is also more time to distribute fluid into compartments of body, not just automatically made into urine

Including the macronutrient, _________ , benefits glycogen replacement when you are in need of replacing fluids lost

carbs

Hyponatremia

deficient sodium in the blood

When are you at risk of over hydration and hyponatremia?

If you are drinking excess water when sweating a lot without salt

Is overhydration and hyponatremia is more common in males or females? Why?

Females- have less water in the body

Why is overhydration an issue

Water wants to get straight into cells

This causes the cell to swell in brain, which can't swell because of skull

SO it makes the situation worse

Low sodium alters membrane potential...T or F

True

Hydrations recs- before exercise

16 oz, 2 hours before exercise

Hydration recs- during exercise

8 oz, every 15-20 min of exercise

Hydration recs- after exercise

20 oz, for every lb of body mass lost during exercise