Lecture 6 Fluids and Electrolytes Flashcards
When body temperature rises towards _______ central fatigue ensues. Fatigue protects against _____
39 degrees Celsius
damage
Factors that affect thermoregulation
What are the two main ways us as humans thermoregulate?
- Must evaporate sweat from the body in order to cool the body down
- Increasing blood flow to skin capillaries is also how our body thermoregulates
Thermoreceptors in the hypothalamus are sensitive to changes in ______ ______ _______
The central thermal controller, or “thermostat” also receives ________ sensory inputs that are capable of modulating the homeostatic regulation of body temperature
internal core temperature
non thermal
Fluid Loss in Sweat Can Be Large
If the exercise is prolonged body temperature increase leads to:
Some people may lose up to ____ to _____L per hour of sweat during strenuous activity in a hot environment
progressive dehydration and loss of electrolytes
2 to 3 L
In less well-trained individuals, they have______ effective ___________
Rises in sympathetic nervous activity causes skin and gut blood vessels to ________ leading to ______ ________ leads to the production of ______ _______ ________ (ROS) which can lead to _________ __________
less, thermoregulation
constrict
cellular hypoxia
reactive oxygen species
membrane damage
The ROS cause preoxidation of lipids in cellular membranes making them _______
In the gastrointestinal tract, this action allows the passage of ________ ______ (endotoxins) from the gut into the systemic circulation, leading to endotoxemia (______ _______________) and a drastic fall in blood pressure
leaky
bacterial toxins
blood
poisoning
training improves temperature regulation during exercise at the same absolute ____ _____
to improve your thermoregulation, you must adequately stimulate thermoregulatory effector responses, to do so, you must exercise at a ____ _____ and increase their body temperature above ______
Acclimation to warm environments requires ______ ____ _____ _______ not just resting in that environment
work rate
high intensity
39 degrees Celsius
exercising in that environment
Training Adaptations
Training helps to maintain constant _____ ____________
Marathon runner have a lower resting ______ _____ and have a lower:
Exercise training improves thermoregulation in the heat by:
Training increase the size of existing _____ ______
Training induced an increase in total b______ v______ and m______ c______ o_______, and so ______ and _______ _______ _______ is better preserved during strenuous exercise in the heat
constant
body temperature
body temperature
sweating and shivering threshold (meaning they start sweating quicker and can tolerate a lower temperature before shivering )
Earlier onset of sweat secretion (once sweat evaporates it helps cool the body down and thermoregulate), and by increasing the total amount of sweat that can be produced.
sweat glands
blood volume and maximal cardiac output
muscle and skin blood flow
Why should athletes heat acclimatize?
to obtain biological adaptations lowering physiological strain and improving exercise capacity in the heat
Recommendations for Heat Acclimation (repeated training in the heat)
- Heat acclimatization session should last ______ ______ per day and should induce an _____ in body core and skin ________ as well as stimulate _______
- Athletes should train in the _____ _______ ____ _____ _______ ______ or if not possible, train indoors in a ____ _______
- Early adaptations are obtained within the first few days, but the main physiological adaptations are not complete until _______ _______
- Ideally, the heat acclimatization period should pass ____ ______ to __________ all benefits
60 minutes
increase
temperature
sweating
same environment as the competition venue
hot room
1 week
2 weeks to maximize all benefits
Acclimated vs Unacclimated conditions
Acclimated + euhydrated =
Unacclimated + euhydrated =
lower body core temperature
higher body core temperature
Dehydration directly impacts:
Increased rate of muscle glycogen _____, and so more rapid glycogen _______, which impairs endurance performance
muscle glycogen stores
use
depletion
What are the absolute recommendations for fluid intake
What are the relative recommendations for fluid intake
500ml consumed 2 hours before exertion and another 500ml be consumed 15 minutes before prolonged exercise
Drink about 6 to 8 ml of fluid per kilogram of body weight about 2 hours before exercise
Preexercise Hyperhydration
Hyperhydration:
hyper hydration can improve thermoregulation by ______ ____ _____ and reducing _____ ________ thereby improving heat dissipation and exercise performance
greater than normal body-water content
expanding blood volume
plasma osmolarity
Glycerol induced hyper hydration
Greater fluid retention is achieved if _______ is added to fluid consumed before exercise. Helps protect against heat stress.
glycerol
H
hydration during exercise
There is prolonged exercise with hydration during exercise. Why?
What is the recommended water intake during exercise?
Hydration causes less glycogen depletion, so prolonged exercise will occur. Dehydration = greater fatigue.
When someone is endurance training with no fluid, they could last 77min. When someone is endurance training with water (2ml/kg body weight every 15 minutes), they’re exercise time increases to 103 minutes
2ml/kg body weight
What is a hypertonic drink?
Why are hypertonic drinks bad during exercise?
How do hypertonic drinks dehydrate you?
The ingestion of hypertonic solution delays what?
10%+ carbohydrate
Hypertonic drinks have too much added carbohydrate, and decrease the amount of water that can be absorbed
water is drawn out of the interstitial fluid and plasma into the lumen of the small intestine by osmosis.
restoration of plasma volume
Therefore, what is the best drink for during and pre exercise?
Hypotonic drinks as their carb content is much lower
Longest exercise time out of
no drink
water
isotonic drink
hypotonic drink
hypotonic drink (adds carbs and electrolytes to your body)
Whats wrong with isotonic drinks, and why do we prefer hypotonic drinks?
isotonic drinks can upset GI tract.
Effective rehydration after exercise
Optimal rehydration after exercise can only be achieved if the _______ lost in sweat is replaced along with the _____
A volume equivalent to at least _______ time the sweat loss must be consumed to ensure complete rehydration
sodium
water
1.5
The problem of Hyponatremia
An electrolyte imbalance commonly called _____ ______ which results from hyponatremia (low plasma sodium) caused by excessive ______ ______ is occasionally reported in endurance athletes
In marathon runners, this is because of the large amounts of loss of ______ _____ coupled with extremely high _______ _______
water intoxication
water consumption
sodium in sweat
water intake
How does dehydration limit thermoregulation?
How does clothing limit thermoregulation?
When we are dehydrated, we produce less sweat, meaning less sweat is evaporated, meaning we lose less heat and become less able to cool our body’s off.
Clothing can limit heat loss as it limits evaporation of sweat from skin, unable to cool the body off. (Depends on the type pf clothing the person is wearing).
