hydration Flashcards
function of aquaporin
transport water across cell membranes in response to osmotic gradients created by active solute transport
total body water equation
0.6 x body weight as water is 60% of our body weight
dehydration clinical threshold
no more than 2% dehydration as it leads to a 10% in performance
how is water distributed
by compartments- Movement of water between the compartments influenced by (i) hydrostatic pressure and (ii) osmotic pressure of the plasma proteins
what is hydrostatic pressure
pressure exerted by a fluid (liquid or gas) at rest due to the force of gravity acting on the fluid’s weight.
what is thermoregulation
a mechanism by which mammals maintain body temperature with tightly controlled self-regulation independent of external temperatures. Temperature regulation is a type of homeostasis and a means of preserving a stable internal temperature in order to survive
what does fluid loss cause
reduce circulating blood/plasma volume, increased cardiovascular strain, increased glycogen depletion, reduced ability to regulate body temperature (hyperthermia), central fatigue.
sweat rates
vary from individual and conditions
warm environment
If temp greater than body temperature- can’t lose heat via radiation/convection and reduced ability to lose heat via sweat in humid conditions
Heat illness
Heat exhaustion
Heat stroke
Those with long events or those who are required to wear heavy clothing at risk
NB acclimatisation, individualised athlete hydration plans, consumption of cooled fluids during exercise, consider electrolyte sources during exercise, ensure euhydration prior to exercise
cold environment
Energy requirements (CHO) increased- need it to maintain core temperature
Risk of hypohydration because of increased diuresis, reduced thirst sensation and altered urge to drink, sweat losses from increased clothing, increased respiration (at altitude)
However, relative to the heat, dehydration of 2-3% will have less of a detrimental effect on performance vs same losses in heat
restoring fluids nb
Restoring fluids maintains normal muscle function, helps prevent a decrease in physical performance and reduces the risk of heat stress.
clinical level of assessing dehydration
- Monitor intake/losses (e.g. urinary output)
- Appearance of skin, mucous membranes
- Laboratory tests- bloods (can measure specific electrolytes also) urine etc.
field level
-Athlete reports of intake/losses
-Pre and post-event weighing of athlete to monitor losses
- Sweat rate
- Urinary colour
euhdydration
optimal or normal hydration
overhydration aka hyponatremia
overhydration= excessive intake of water that dilutes the levels of sodium in the blood
Sodium is an essential electrolyte that helps regulate the balance of fluids in and around cells. When sodium levels become dangerously low due to overhydration, it can lead to hyponatremia, which can have serious health consequences.
Refractometer
to measure urine specific gravity
hypohydration
is when the body doesn’t receive enough water to compensate for the fluid losses it experiences during various activities
hypohydration symptoms
increased core body temperature,
decreased blood pressure (hypotension),
decreased sweat rate, rapid breathing, fast heartbeat, dizziness or light-headedness,
irritability, confusion, delirium,
lack of urination,
sunken eyes,
shock,
unconsciousness,
dry, wrinkled skin that doesn’t “bounce back” quickly when pitched,
reduced stroke volume and cardiac output,
reduced blood flow to muscles
rhabdomyolysis
rapid breakdown of skeletal muscle tissue, causing the release of muscle cell contents into the bloodstream.
factors affecting during exercise hydration
Rules and format of sport
Athlete preferences- most athletes may tolerate 200-300mls every 15 mins, but this will vary (AIS, 2009)
Temperature of the drink – may further improve performance in heat by reduction in core temperature
Formulation of the drink – i.e. inclusion of CHO in drink as a further ergogenic aid.
Electrolyte composition of the drink
Hydration also a concern for athletes in wet environments and air-conditioned stadiums
post exercise hydration needs
Will need water/fluid and sodium source to minimise urinary losses
Sodium- helps to retain fluids
For effective rehydration, need to consume greater amount of fluids than lost
Hyponatremia
is the reduction of the sodium concentration in the blood
(< 135 mmol/l)
