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Flashcards in 3. hydration Deck (28):
1

importance of hydration (4)

1. maintains blood volume and osmolarity
2. remove wastes and toxins (filtration in kidneys)
3. ensures proper neural conduction for muscle function
4. regulates body temp

2

dehydration is associated with (2)
- result
- compensation

1. increased core temp
2. decreased blood volume (decreased stroke volume)

* decreased muscular endurance and strength
- HR increases in attempt to compensate

3

dehydration and % body mass loss
- 1-2%

- decrease temp control
- increase HR

4

dehydration and % body mass loss
3%

- 10% decrease in muscle performance

* not clinical problem but strong effect

5

dehydration and % body mass loss
4-6%

- decrease muscle strength and hand eye coordination

6

dehydration and % body mass loss
+6%

decrease blood volume
increase respiration rate
nausea and confusion

7

dehydration and % body mass loss
+10%

heat stroke
fainting
exhaustion

8

purpose of sweating

decrease core body temp

9

if not rehydrating when sweating

decrease in body fluids
leads to decrease in blood volume
further increases core body temp

10

volume of fluid that can be lost per hour of exercise
- terms of body mass

1-2 leters

~2-3% body mass/hour (assuming 67kg athlete)

11

factors that affect dehydration
- environmental
- individual

environment
- hot and humid conditions
- clothing/equipment
- lack of rehydration

individual
- effort
- training level
- sweat rate (genetic)

12

physiological impact of dehydration (8)
- increased (5) and decreased (3)

increased
- plasma osmolarity
- HR
- skin and core temp
- RPE (rating of perceived exhaustion)
- CHO oxidation (glycogen stores deplete faster)

decreased
- plasma volume
- cardiac filling
- sweat rate and skin blood flow

13

study results
- hydration status and what athletes voluntarily drink
- running time vs core temperature

60 mins of running
- athletes "voluntarily" drink less than 50% of their body fluid loss during exercise

*water ad libitum (voluntary drinking)

14

critical temp for experiencing central fatigue

~39C

15

water ad libitum

voluntary drinking during exercise
- what we choose to drink

16

study result
- 10 well trained cyclists
- 5k hill climb
- either euhydrated (EUH - normal hydration) or dehydrated (DEH - 1% of body mass)

EUH - faster (5.8%)
DEH - higher core temp, RPE (rating of perceived exhaustion), decreased sweat rate

17

measuring sweat loss volume

total sweat volume loss
(pre-exercise mass) - (post exercise mass) + (fluid intake) + (urine output)

18

goals in preventing dehydration during exercise (4)

1. drink fluids at least 80% of sweat volume loss
- aim for 60-90min
- heat increases CHO use

19

problems with over drinking

hyponatremia
- low blood sodium

20

benefits of CHO in fluids

- shown to enhance performance in exercise greater than 60-90min
- heat increases CHO use
- CHO used 2-4 times faster with intermittent sprints (stop and go sports)
- enhances recovery

21

study results
- endurance trained men exercising at 69% VO2max
- 8% carb vs placebo drink

time to exhaustion increased 30%
- plasma glucose remained above resting while placebo initial increase before fast decline

22

study results
- hockey players on ice scrimmage
- no fluid (NF) vs CHO/electrolyte soln

no fluid
- approx 2% body mass decrease
- slightly higher sweat rate
- higher core temp during
- impaired drill performance

23

benefits of sport drinks

flavour encourages drinking

contains 2-6% extra energy
- extra energy in muscle and brain
- maintains blood glucose levels

similar absorptive capacity as water

contains electrolytes
- Na, Cl, K
- replace salt loss in sweat
- retain fluid in body and blood

24

CHO mouth rinsing mechanism
- not swallowing

mental/cognitive stimulation of CNS by oral receptor exposure to CHO with

25

study results
- CHO mouth rinsing
- 2 performance trials with carb rinse (6.4%) and placebo
- rinse 5sec every few mins
- approximately 1hr of exercise

CHO rinse significantly improved performance
- results highly variable

26

controversy and question with CHO mouth rinsing
- possible benefits

- studies 1hr and stop/go events)
- duration of rinse
- frequency
- muscle and liver glycogen stores
- duration of fasting before trial
- type of activity

benefits?
- may not like stomach full of fluid
- may alter sensitivity of receptors

*

27

recommended fluid intake before exercise
- how quickly dehydrated subjects return to hydrated state

600-700mL of water or sport drink approximately 60-90mins prior
- all dehydrated subjects returned to hydrated status in 45mins
- hydration status assessed by measuring urine specific gravity

28

optimal fluid intake goals 'after' training

goal
- replace lost fluid and electrolyte stores
- within 2hrs following
- need to also help body re-synthesize liver and muscle glycogen stores