Fluids and perfomance Flashcards
What are the 2 fluid categories?
ECF and ICF
Main electrolytes ECF:
Na+ and Cl-
Main electrolytes ICF:
K+
Explain the function of electrolytes
Help maintain body fluid balance by keeping water within a particular body compartment
What is osmosis?
the diffusion of water across a membrane in response to osmotic pressure, caused by an imbalance of molecules on either side of the membrane
What is osmoregulation?
is the process of maintenance of mineral ions and water balance across membranes within the body’s fluid
What adds a greater effect on osmotic pressure?
Electrolytes
What is osmolarity?
number of solute particles in 1L of solvent
What is osmolality?
number of solute particles in 1kg of solvent
Explain osmotic regulation in the cell
- hypotonic: swollen cell
- isotonic: normal looking cell
- hypertonic: shrivelled cell
What increases the sweat threshold?
dehydration
What decreases the sweat threshold?
acclimatisation and exercise training
What type of sports drink would be most appropriate when hydration is more important than refuelling?
Hypotonic drink <4% CHO
Name 2 components of a sports drink that would delay gastric emptying
> 8% CHO
Osmolality: increased solute concentration
What is the effect of high-intensity exercise on gastric emptying?
Slows gastric emptying during and after exercise
Outline the physiological effects of dehydration that would contribute to impaired exercise performance
Mental haziness
Impaired psychomotor ability
Which two main factors contribute to the development of hyponatremia during exercise in the heat?
- excessive fluid intake
- impaired urinary water excretion
- persistent secretion of ADH
Outline some of the effects of dehydration (%) on performance
- 3-5% dehydration results in lowered VO2max due to lowered blood volume and reduced maximal cardiac output
- 3-7% dehydration loss of bm decreases endurance performance
- running or cycling sprints: lighter body mass may sometimes counteract the effects of dehydration
Regarding hydration, what would the effect of ingesting a sports drink with lower osmolality than bodily fluids be?
(Hypotonic drink <4% CHO) Rapid absorption, suitable for intense exercise <1 hour.
The preferred option if the primary goal is hydration.
Outline the potential sources of error when using loss of body mass solely to calculate sweat rates
- water produced due to substrate oxidation
- water stored with glycogen
Briefly outline a rapid rehydration strategy following a dehydrating exercise
- Drink 1.5L of fluid for each kg of body weight lost
- Include sodium in rehydration solution; more fluid is retained when sodium content >50mmol/L
- Drink containing glucose and electrolytes
What are the advantages of including highly branched glucose polymers in sports drinks?
- provide more energy, less sweet taste
- lower osmolality than body fluids, therefore accelerate gastric emptying
- taste advantages, reduce GI distress
What is the purpose of employing pre-cooling methods before exercise?
- to reduce body temperature prior to exercise, therefore decrease heat stress, improve exercise tolerance to heat and performance
- can redistribute blood to working muscles, preserve optimum temp for enzymatic reactions, delay volitional fatigue
True or false
2% loss in body mass impairs performance tasks that require attention, psychomotor and immediate memory skills, perception, etc
True
Recommendations for pre-exercise hydration
- 500ml water or sports drink the night before the event
- further 500ml water on awakening
- further 400-600ml water or sports drink 20-30min before the event
- if exercising in the heat, an additional 250-500ml before exercise
- add salty snacks
True of false
Creatine increases short-term intracellular water uptake and fluid retention
True
How does sodium aid in hydration?
stimulates ADH secretion - renal water reabsorption - reduced urine output
How does glycerol aid in hydration?
- improved time to exhaustion
- GI issues
- body mass gain
True or false
1L sweat removes 580 kcal heat from body via evaporation
True
Fluid replacement strategies
during exercise
Need to be adapted to individual’s sweat rate, duration, clothing, weather conditions, genetic predisposition, training status, heat acclimatisation
Mention some practical cooling strategies
- cooling vest (pre-cooling)
- cold water immersion (pre-cooling)
- Nitrogen vapour shower (pre-cooling)
Effect of ingesting a sports drink with similar osmolality to bodily fluids
(Isotonic drink 4-8% CHO)
It is intended to quench thirst and provide energy. Suitable for endurance sports
Effect of ingesting a sports drink with greater osmolality than bodily fluids
(hypertonic drink >8% CHO) Primarily intended to supply energy, thirst-quenching is secondary. Gastric emptying and absorption may be delayed. May be effective for longer-term rehydration
What is the optimal CHO concentration in a sports drink?
6-8%
Sports drinks/rehydration
solutions should contain:
- 4-8g CHO from multiple sugars
- 500-700 mg/L sodium
A good oral hydration solution should:
- empty rapidly from the stomach
- enhance intestinal absorption
- Promote fluid retention
What are the best tests to assess hydration status?
Plasma and serum osmolality
Describe the benefits of sports drinks
- they provide fluids for rehydration
- they provide electrolytes to enhance intestinal water absorption
- they provide carbohydrates for energy
Sports drinks contain sodium because:
- increase fluid retention
- provide electrolytes lost in sweat
Carbohydrate mouth rinsing may be effective at improving cycling performance because:
Glucose sensors in the mouth activate reward centres in the brain
