Lecture 6 Fluids and Electrolytes

Question 1

When body temperature rises towards _______ central fatigue ensues. Fatigue protects against _____

Answer 1

39 degrees Celsius

damage

Question 2

Factors that affect thermoregulation

What are the two main ways us as humans thermoregulate?

Answer 2

1. Must evaporate sweat from the body in order to cool the body down
2. Increasing blood flow to skin capillaries is also how our body thermoregulates

Question 3

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

Answer 3

internal core temperature

non thermal

Question 4

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

Answer 4

progressive dehydration and loss of electrolytes

2 to 3 L

Question 5

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 _________ __________

Answer 5

less, thermoregulation

constrict

cellular hypoxia

reactive oxygen species

membrane damage

Question 6

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

Answer 6

leaky

bacterial toxins

blood
poisoning

Question 7

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

Answer 7

work rate

high intensity

39 degrees Celsius

exercising in that environment

Question 8

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

Answer 8

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

Question 9

Why should athletes heat acclimatize?

Answer 9

to obtain biological adaptations lowering physiological strain and improving exercise capacity in the heat

Question 10

Recommendations for Heat Acclimation (repeated training in the heat)

1. Heat acclimatization session should last ______ ______ per day and should induce an _____ in body core and skin ________ as well as stimulate _______
2. Athletes should train in the _____ _______ ____ _____ _______ ______ or if not possible, train indoors in a ____ _______
3. Early adaptations are obtained within the first few days, but the main physiological adaptations are not complete until _______ _______
4. Ideally, the heat acclimatization period should pass ____ ______ to __________ all benefits

Answer 10

60 minutes

increase

temperature

sweating

same environment as the competition venue

hot room

1 week

2 weeks to maximize all benefits

Question 11

Acclimated vs Unacclimated conditions

Acclimated + euhydrated =

Unacclimated + euhydrated =

Answer 11

lower body core temperature

higher body core temperature

Question 12

Dehydration directly impacts:

Increased rate of muscle glycogen _____, and so more rapid glycogen _______, which impairs endurance performance

Answer 12

muscle glycogen stores

use

depletion

Question 13

What are the absolute recommendations for fluid intake

What are the relative recommendations for fluid intake

Answer 13

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

Question 14

Preexercise Hyperhydration

Hyperhydration:

hyper hydration can improve thermoregulation by ______ ____ _____ and reducing _____ ________ thereby improving heat dissipation and exercise performance

Answer 14

greater than normal body-water content

expanding blood volume

plasma osmolarity

Question 15

Glycerol induced hyper hydration

Greater fluid retention is achieved if _______ is added to fluid consumed before exercise. Helps protect against heat stress.

Answer 15

glycerol

Question 16

H

Question 17

hydration during exercise

There is prolonged exercise with hydration during exercise. Why?

What is the recommended water intake during exercise?

Answer 17

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

Question 18

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?

Answer 18

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

Question 19

Therefore, what is the best drink for during and pre exercise?

Answer 19

Hypotonic drinks as their carb content is much lower

Question 20

Longest exercise time out of

no drink
water
isotonic drink
hypotonic drink

Answer 20

hypotonic drink (adds carbs and electrolytes to your body)

Question 21

Whats wrong with isotonic drinks, and why do we prefer hypotonic drinks?

Answer 21

isotonic drinks can upset GI tract.

Question 22

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

Answer 22

sodium

water

1.5

Question 23

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 _______ _______

Answer 23

water intoxication

water consumption

sodium in sweat

water intake

Question 24

How does dehydration limit thermoregulation?

How does clothing limit thermoregulation?

Answer 24

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).