Hydration Flashcards
Osmosis
the movement of water across a semi-permeable membrane from where the solute concentration is low to where it is higher
Hypertonic solution and osmosis
solute concentration greater, water will move into solution
Hypotonic solution and osmosis
solution concentration lower, water will move out of solution
What do fluid losses do to the body
reduce circulating blood volume, increased cardiovascular strain. increased glycogen depletion, decreased ability to regulate body temperature
Approx how much sodium loss per litre of sweat
40-50 mmol/L
What level of dehydration effects the body
> 2%
Physiological impacts of dehydration
increase thermoregulatory stress- reduced ability to regulate body temperature.
Pressure on CVS- reduced plasma volume, increase HR.
Accelerated glycogen depletion.
CNS effects
warm temperature effects
if temperature greater than internal body temperature- cant lose heat via radiation/convection and reduced ability to lose heat via sweat if humid conditions
Heat illness
Heat exhaustion
NB- acclimitisation, individualised athlete hydration plans, consumption of cooled fluids during exercise, ensure euhydration prior to exercise
Cold temperature effects
Energy requirements (CHO) increased- need to maintain internal core temp
Hypohydration risk- increased diuresis. reduced thirst sensation and altered urge to drink.
Sweat loss increase- heavy clothing
Relative to heat, dehydration of 2-3% will have less effect on performance vs same losses in heat
Clinical assessment of dehydration
monitor intake/loss.
appearance of skin, mucous membranes
lab tests
Athletic/ ‘field’ assessment of dehydration
pre and post weighing to monitor loss
sweat rate
urinary colour
sensation of thirst not a reliable stimulus
Dehydration
process of losing body water
Hypohydration
uncompensated loss of body water
pre exercise hydration
5-10 mls per kg in 2-4 hrs prior to event
post exercise hydration
need to consume greater amount than loss.
1-1.5 litre per kg of loss
