3. hydration

Question 1

importance of hydration (4)

Answer 1

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

Question 2

dehydration is associated with (2)

• result
• compensation

Answer 2

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

• decreased muscular endurance and strength
• HR increases in attempt to compensate

Question 3

dehydration and % body mass loss

- 1-2%

Answer 3

• decrease temp control

- increase HR

Question 4

dehydration and % body mass loss

3%

Answer 4

• 10% decrease in muscle performance

* not clinical problem but strong effect

Question 5

dehydration and % body mass loss

4-6%

Answer 5

• decrease muscle strength and hand eye coordination

Question 6

dehydration and % body mass loss

+6%

Answer 6

decrease blood volume
increase respiration rate
nausea and confusion

Question 7

dehydration and % body mass loss

+10%

Answer 7

heat stroke
fainting
exhaustion

Question 8

purpose of sweating

Answer 8

decrease core body temp

Question 9

if not rehydrating when sweating

Answer 9

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

Question 10

volume of fluid that can be lost per hour of exercise

- terms of body mass

Answer 10

1-2 leters

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

Question 11

factors that affect dehydration

• environmental
• individual

Answer 11

environment

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

individual

• effort
• training level
• sweat rate (genetic)

Question 12

physiological impact of dehydration (8)

- increased (5) and decreased (3)

Answer 12

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

Question 13

study results

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

Answer 13

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

*water ad libitum (voluntary drinking)

Question 14

critical temp for experiencing central fatigue

Answer 14

~39C

Question 15

water ad libitum

Answer 15

voluntary drinking during exercise

- what we choose to drink

Question 16

study result

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

Answer 16

EUH - faster (5.8%)

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

Question 17

measuring sweat loss volume

Answer 17

total sweat volume loss

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

Question 18

goals in preventing dehydration during exercise (4)

Answer 18

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

Question 19

problems with over drinking

Answer 19

hyponatremia

- low blood sodium

Question 20

benefits of CHO in fluids

Answer 20

• 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

Question 21

study results

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

Answer 21

time to exhaustion increased 30%

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

Question 22

study results

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

Answer 22

no fluid

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

Question 23

benefits of sport drinks

Answer 23

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

Question 24

CHO mouth rinsing mechanism

- not swallowing

Answer 24

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

Question 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

Answer 25

CHO rinse significantly improved performance | - results highly variable

Question 26

controversy and question with CHO mouth rinsing | - possible benefits

Answer 26

- 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 *

Question 27

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

Answer 27

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

Question 28

optimal fluid intake goals 'after' training

Answer 28

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