Week 9 Flashcards

1
Q

How much of the adult body is water and how much approximately water wise is lean mass and fat mass?

A

50-70% of adult body is water

Around 73% of lean body mass is water and around 5-10% of fat mass = water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Water function?

A

Helps regulate temperature, useful for nutrient transport, helps with biochemical reactions, medium for reactions and provides protection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Sources of water losses and production- look at table on slides for values

A

Resp losses, urinary losses, fecal losses, insensible losses, metabolic production.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What can the extremes of water loss be upto?

A

Can be upto 6.5 litres of water loss a day.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are sweat rates like in hot and humid conditions?

A

Sweat rates are extremely high and sweat rates of over 1 litre per hour are not uncommon.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why do we sweat during exercise?

A

We produce heat during exercise.
When we exercise about 4kcal of heat are produced and only 1 is used for mechanical work.
Most of the heat goes to the bodies core- hypothalamus detects increased temperature and causes increased blood flow to the skin and causes a sweat response.
Sweating helps stop excessive rises in temperature (hyperthermia)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is normal body temp range and what is exercising body temperature range?

A

Normal body temperature is between 36 and 38 degrees and exercising body temp range = 38-40.
1 litre of sweat evaporated removes 573 kcal of heat from the body.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is net water balance?

A

It is the difference between fluid intake / production and fluid loss.
Typically it is well maintained on a day to day basis.- thirst and hunger drives. Net body water balance can be challenged in high sweat periods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is ad libitum drinking?

A

Ad libitum drinking is drinking to thirst e.g. drinking when you want.
Ad libitum drinking during exercise can cause/ lead to a body water deficit- can lead to greater than a 2% loss in body mass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Dehydration- what is it?

A

Dehydration often also called hypohydration. It = a body water deficit larger than normal daily fluctuation.

Body mass changes gives the most sensitive and simplest measure to determine acute changes in body water.

Acute changes means greater than 2% body mass mass decrease= 90% chance that body water deficits = big enough to be known as dehydration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When does hypohydration happens?

A

Hypohydration happens is lots of water loss happens through sweating.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is sweat loss?

A

Water loss from the water component of blood plasma. Sweat = hypotonic compared to plasma so plasma osmolality increases.

With blood if yu spin in centrifuge heaviest parts go to the bottom e.g. rbc’s and plasma where the waters from goes to the top.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Differences between sweat and plasma

A

Sweat and plasma are not the same. Sweat is not the same as plasma as does not contain many of the parts plasma does. Sweat has lower concentration of electrolytes such as sodium than plasma does.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What’s plasma osmolality?

A

When plasma volume drops and relative amount of electrolytes is less it has a concentrating effect called plasma osmolality. Increased plasma osmolality is a common way to know dehydration is occuring.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Effect of sweat loss on cardiovascular strain

A

Sweat loss decreases plasma volume and increases cardiovascular strain. Another issue is that redistribution of blood flow to the skin to help with thermoregulation can also have the effect of increasing cardiovascular strain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

HR effect due to dehydration.

A

HR will often increase with dehydration. Exercising in heat increases skin temperature and increases sweating. Heart tries to pump more blood to the skin and muscles to meet their demands.- puts a larger strain on the cardiovascular system. At higher temperatures dehydration has a negative performance effect. Dehydration effects = tolerable in lower temperatures.

17
Q

Potential mechanisms of impaired aerobic performance in warm-hot conditions

A
Cardiovascular
CNS
Peripheral muscle factors
Psychological
Respiration

Dehydration enhances these mechanisms although cardiovascular strain is likely a critical primary factor.

18
Q

Does hypohydration always impair performance?

A

1-2 % body mass hass loss has little effect
2-3% -may causes decreased aerobic performance (more often in heat) and can decrease sport specific skills. Little effect of sprinting or cognitive functioning without heat stress- though if there is heat stress can reduce cognitive function.

In greater than 3% impaired cognitive function (even in temperate)

3-4% has little effect on strength and power.

19
Q

Excessive dehydration and overhydration

A

Dehydration can increase perception of effort fatigue. Should come up with individualized fluid and hydration plans to replace as much of the sweat lost as is practical. Dehydration negatively affects performance and should hydrate in some situations during exercise. Do not want excessive dehydration or over hydration

20
Q

How much fluid should athlete drink post exercise?

A

After exercise athlete should restore fluid balance by drinking an amount of fluid equivalent to around 125-150% of remaining fluid deficit eg. 1.25-1.5L for every kilogram of body weight lost

21
Q

Appropriate fluid intake what is it?

A

Appropriate fluid intake is consuming enough fluid to be hydrated.
Based on net water losses ranging from 1550 ml to to 6730 ml a day. Large individual variation but knowing what to look for is important. Staying hydrated is very important but how much you need to drink is a very individual process.

22
Q

Plasma osmolality measuring-

A

Plasma osmolality is the best static physiological index of hydration status
Osmolality= measure of total dissolved particle concentration generally around 275-295 mOsm/kg.

23
Q

Dynamic dehydration

A

Can be tracked well with body mass change (in energy balance), plasma osmolality, urine specific gravity (urine density relative to water- where water = 1.00, eudehydrated at values of 1.003-1.035

24
Q

What is the best index of dehydration status?

A

The best index of dehydration status = plasma osmolality.- how concentrated a plasma element is. Values of 295 ml osmoles per kg of water= sufficiently hydrated. Blood sample is not the most convenient though does give the best diagnosis. EU = more practical though is not as useful as plasma osmolality

25
Q

Increases in reference change value and the dehydration likelihood scale.

A

Increase in 7 mmol/kg or a decrease in 2% of body mass means you are 90% more likely to be dehydrated.

26
Q

Hydration guidelines for competition

A

2-4 hours pre-event need 5-10 ml of fluid per kg of body weight. (sodium, salt snacks or small meals might help.) Drink more fluid if there is no urine or if urine is dark.

During exercise drink sufficient fluid to limit fluid losses to less than 2% body mass and limit excessive electrolyte imbalance. Pre and post exercise weighing can help in estimation.
Generally 0.4- 0.8 l/h .
Greater than 2hours or salty sweaters add sodium to the drink. Greater than 1 hour maybe consider carbohydrate addition to drink.

Post exercise- rapid recovery - within 12 hours consume 1.25-1.5 L for each kg body mass lost and consume sodium.
More recovery time: resume dietary practices and extra plain water.

27
Q

Why consume sodium?

A

Sodium helps with fluid retention and in some individuals help maintain sodium balance in the body.
Sodium in sports drinks encourages thirst making you want to drink more. Post exercise sodium helps regain fluid balance

28
Q

How much to replace fluids?

A

In study post exercise 100% replacement of fluids were still a bit dehydrated due to the continuous loss of fluids through urine etc. 150% hydration in fluid balance shows no sign of dehydration. Sodium is extremely important for hydration.

29
Q

Sweat rate equation

A

Weight loss

+ volume consumed - urinary losses / exercise duration.