Hydration Flashcards
Purpose of water in body
- cushion/protection
- water and electrolyte balance (osmotic pressure)
- carries oxygen, nutrients, hormones, etc
- carries waste products away for excretion
- solvent for minerals, vitamins, AA, glucose
- functioning of our senses
- regulation of body temp
When does heat production increase
Higher BMR, infectious disease, shivering, exercise
60-80% of metabolic heat produced during exercise is converted
To heat (within the body)
How is heat removed from body
Radiation, conduction, convection and evaporation
In sport and physical activity what would impact our ability to sweat (evaporate water)?
- physical environment (heat, humidity)
- hydration
- intensity, duration, body size, training, fitness levels
- equipment (what wearing)
What is most essential nutrient
Water
Losses of water
Perspiration, respiration, urine, feces
What produces water
Metabolism
AI for water
Adult males= 3.7L
Adult females= 2.7L
UL for water
No UL set
What does water include
All foods, beverages and water
Anything liquid at room temp
How does metabolism produce water
Water is by product when break down macronutrients for energy
What is water held in body with
Protein, CHO and electrolytes
How much of body is made up of water
50-60%
What is water regulated by
Regulated by kidneys (euhydration or normohydration)
How do you know if you’re adequately hydrated
Thirst mechanism
Color of urine
When is best time to check urine
Right in morning
3 hydration statuses
Hypo- or dehydration
Euhydration
Hyperhydration
Effects of hypohydration
Detrimental to performance
Heat illness, sickness
Lose consciousness
Death
Effects of euhydration
Good performance
Effects of hyperhydration
No advantage
Hyponatremia
Low sodium in blood
- if sweating lots cant just have plain water
Effects of hyponatremia
Confusion, fainting
Fatal is misdiagnosed
Practical hydration goals
- getting comfortable with hydration during intensity
- consume fluids to match sweat rates (or minimize drop in BW)
How much water include with each meal +snack
250-500ml
When training in heat-
Monitor for signs of dehydration
How much water or fluids with recovery
500-750ml
How much sweating may reduce performance
As little as 2% loss of body weight due to sweating
What exercise does loss of BW due to sweating affect most
Most severe on aerobic endurance performance
- especially hot, humid environments
2 types of loss of BW due to sweating
Voluntary and involuntary
When is it likely that fluid deficits during exercise will reach levels likely to effect performance
When exercise duration exceeds 60mins and when ambient temperature is high
Factors to think about (sweating)
Hydration status at start of training
Equipment worn
Cold temperatures
Training status/individual sweat rates
How can hydration status be measured
Assuming athlete us in energy balance, daily hydration can be estimated by tracking early morning body weight (on very accurate scale) measured upon waking after morning voiding
Acute changes in BW=
A shift in body water
What else can be used to measure hydration status
Specific gravity and urine osmolality
osmolality
Refers to amount, or concentration of dissolved substances (solute) in a solution (osmol/kg solvent)
When does osmolality increase and decrease
Increase with dehydration (hypertonic)
Decreases with overhydration (hypotonic)
Water movemetn from hypo to hypertonic
Osmolarity
Number of solute particles per litre of solution
Value <1.020
Considered adequate for hydration status; usually measured upon waking
Sweat rate calculation
- Weigh prior to workout, record in kg (1kg = approx 1L)
- Weigh post workout, record in kg
- Sweat loss in litres= BW before- BW after (add any fluids consumed during training)
- Divide sweat loss by length of workout (min or hr)
Pre workout 74kg
Post workout 73kg
500ml water consumed in 1 hr training
74kg - 73kg = 1 + 0.5L = 1.5L/hr
What does the assumption 1kg=1L ignore
Other confounding factors: fuel use, CHO oxidation
Limitation with fluid balance assessment: what are conditions that are specific in which testing took place
Temperature
Training status
Humidity
Intensity/duration
Hydration status at start
Acclimitization
As bw increases what happens to sweating
Increases
As intensity increases what happens to sweating
Increases
As temperature increases what happens to sweating
Increase
The old ACSM recommendations for hydration
Athletes should aim to replace 100% of their BW losses during exercise and to ingest supplemental sodium (no performance advantage)
New ACSM recommendations for hydration
Fluids should be replaced at a rate that will insure that BW losses during exercise do not exceed 2%
Dehydration and the effects on exercise performance
- impaired performance
- greater reliance on CHO for fuel
- might degrade mental/cognitive performance
- impair vigilance (errors)
-impair reaction time - may be factor in GI distress
- increased RPE
Does dehydration matter
- in reality performance impact of dehydration is less clear
Athletes complete events with variable fluid intake
What are guidelines for dehydration and reality
Limit %BW loss to within 2% of starting BW
Reality: large variability with % change in BW from -8% to +5% at end of marathon
Physiological effects of dehydration
Decrease plasma volume-> increase plasma osmolality + blood viscosity -> decrease central blood volume + filling of heart -> decrease SV + increase HR -> decrease cardiac output -> decrease blood flow + sweat rate
What does all the physiological effects do
Increase core temperature
Effects of starting a training session in a dehydration state (hypohydration)
3.2% drop in mean power output
Impairs endurance performance
What is sweat made up of
99% water and 1% electrolytes
Major electrolytes in sweat
Sodium and chloride
What is sodium content of sweat
Variable, depends on training status, heat acclimitization, hydration status
If sweating lots what do we need to replace
H20 and electrolytes
Can’t just drink water
Exercise associated hyponatremia
Low concentration of sodium in blood
<135mmol/L
What are symptoms of hyponatremia
- very similar to dehydration
- often can be asymptomatic (biochemical hyponatremia)
What is hyponatremia typically associated with
- endurance events (long duration, low intensity)
- increased availability of fluids (before/during/after)
- slower athletes
- lighter body weight/smaller individuals/females
Signs and symptoms noted with serum sodium <130mmol/L
Bloating
Puffiness of hands and feet
Nausea
Vomiting
Headache
Signs and symptoms of severe cases <120mmol/L
Seizures
Coma
Respiratory arrest
Permanent brain damage
Death
Electrolytes
Substance which, in solution, conducts an electrical current
Primary electrolytes
Sodium, chloride, bicarbonate, surface, magnesium, calcium
AI for sodium and what it doesnt take into account
1,500mg/day
No allowances for increased sodium losses with sweating
Takes into consideration inactive adults
UL of sodium and daily value used on food labels
2,300 mg/day UL
2,400 DV
Do other electrolytes have significant role in hydration before, during, or after
No emerging evidence to suggest anything other then sodium has significant role
Major function of sodium
Principe electrolyte in extracellular fluids, serves to maintain normal body fluid balance & osmotic pressure
What is sodium critical for
Nerve impulse transmission and muscle contraction
What is sodium also a component of
Sodium bicarbonate
- helps maintain normal acid base balance
During intense exercise what happens to sodium concentration
Increases in blood to help maintain blood volume
What else increases during exercise to conserve body water and Na supplies
Antidiuretic hormone (ADH)/vasopressin
What do endurance athletes with high sweat rate/salty sweat have to do
Need additional sodium during and after exercise
What should be included during endurance sport
Sodium if sweat losses high especially if exercise lasts more than 2 hr
Before exercise for sodium recommendations
Foods/fluids containing sodium can help retain fluids consumed prior to exercise to establish euhydration
Sodium reconditions for after exercise
Restoration and replacement of sodium is prerequisite for effective restoration and maintenance of euhydration
Is coconut water a good sodium and hydration drink
Good for hydration not a lot of sodium
Need to eat sodium product
