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Nutr 4210 > 3. hydration > Flashcards

3. hydration Flashcards

1
Q

importance of hydration (4)

A
  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
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2
Q

dehydration is associated with (2)

  • result
  • compensation
A
  1. increased core temp
  2. decreased blood volume (decreased stroke volume)
  • decreased muscular endurance and strength
  • HR increases in attempt to compensate
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3
Q

dehydration and % body mass loss

- 1-2%

A
  • decrease temp control

- increase HR

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4
Q

dehydration and % body mass loss

3%

A
  • 10% decrease in muscle performance

* not clinical problem but strong effect

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5
Q

dehydration and % body mass loss

4-6%

A
  • decrease muscle strength and hand eye coordination
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6
Q

dehydration and % body mass loss

+6%

A

decrease blood volume
increase respiration rate
nausea and confusion

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7
Q

dehydration and % body mass loss

+10%

A

heat stroke
fainting
exhaustion

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8
Q

purpose of sweating

A

decrease core body temp

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9
Q

if not rehydrating when sweating

A

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

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10
Q

volume of fluid that can be lost per hour of exercise

- terms of body mass

A

1-2 leters

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

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11
Q

factors that affect dehydration

  • environmental
  • individual
A

environment

  • hot and humid conditions
  • clothing/equipment
  • lack of rehydration

individual

  • effort
  • training level
  • sweat rate (genetic)
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12
Q

physiological impact of dehydration (8)

- increased (5) and decreased (3)

A

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
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13
Q

study results

  • hydration status and what athletes voluntarily drink
  • running time vs core temperature
A

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

*water ad libitum (voluntary drinking)

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14
Q

critical temp for experiencing central fatigue

A

~39C

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15
Q

water ad libitum

A

voluntary drinking during exercise

- what we choose to drink

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16
Q

study result

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

EUH - faster (5.8%)

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

17
Q

measuring sweat loss volume

A

total sweat volume loss

pre-exercise mass) - (post exercise mass) + (fluid intake) + (urine output

18
Q

goals in preventing dehydration during exercise (4)

A
  1. drink fluids at least 80% of sweat volume loss
    - aim for 60-90min
    - heat increases CHO use
19
Q

problems with over drinking

A

hyponatremia

- low blood sodium

20
Q

benefits of CHO in fluids

A
  • 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
Q

study results

  • endurance trained men exercising at 69% VO2max
  • 8% carb vs placebo drink
A

time to exhaustion increased 30%

- plasma glucose remained above resting while placebo initial increase before fast decline

22
Q

study results

  • hockey players on ice scrimmage
  • no fluid (NF) vs CHO/electrolyte soln
A

no fluid

  • approx 2% body mass decrease
  • slightly higher sweat rate
  • higher core temp during
  • impaired drill performance
23
Q

benefits of sport drinks

A

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
Q

CHO mouth rinsing mechanism

- not swallowing

A

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

25
Q

study results

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

CHO rinse significantly improved performance

- results highly variable

26
Q

controversy and question with CHO mouth rinsing

- possible benefits

A
  • 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
Q

recommended fluid intake before exercise

- how quickly dehydrated subjects return to hydrated state

A

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
Q

optimal fluid intake goals ‘after’ training

A

goal

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

Nutr 4210 (16 decks)

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