Hydration - Health and Phys. Activity Flashcards
What are the purposes of water in the body?
- cushion/protection
- water & electrolyte balance (osmotic pressure)
- carries oxygen, nutrients, hormones, etc.
- carries waste products away for excretion
- solvent for minerals, vitamins, amino acids, glucose
- functioning of our senses
- regulation of body temperature
What things may increase body temperature?
higher BMR, infectious disease, shivering, exercise
What % of metabolic heat produced during exercise is converted to heat?
60-80%
How is heat removed?
via radiation, conduction, convection, and evaporation
In sport and physical activity what would impact our ability to sweat (evaporate water)?
- current hydration levels
- humidity
- weather (heat/cold, humidity, altitude)
- uniforms or equipment
- duration and intensity
- fitness level of the person (not necessarily, but can be a factor)
What are the ways that water is lost from the body?
perspiration, respiration, urine, feces
Does metabolism produce or lose water?
metabolism can produce water
What is the adequate intake of fluids for adult males and females? Does this include only water drank?
adult males = 3.7L
adult females = 2.7L
includes all foods, beverages, and water
Is there a set upper limit for water?
no UL
Is water a reactant or product in metabolism?
product
How is water stored? (With what?)
stored in body with protein, carbohydrates, and electrolytes
Water composes what % of adult body? What does this depend on?
50-60%
depends on body composition
Water storage is regulated by what organ?
Regulated by the kidneys
What is euhydration and normohydration?
Euhydration: state of optimal total body water content as regulated by the brain
Normohydration: normal hydration
In class discussion - how do we know if we’re hydrated, and how can we monitor our hydration?
hydrated - not thirsty
monitor - looking at urine colour
When urine is at its darkest (brownish yellow), what may this indicate?
May indicate blood in urine or kidney disease
Why might the colour in toilet not be accurate of your hydration level?
Certain foods, medications and vitamin supplements may change your urine colour even if you are hydrated.
Colour will be diluted with water in the toilet.
What are the dangers of hypohydration or hyperhydration?
detrimental to performance
heat illness, sickness
lose consciousness
death
What is hyponatremia? What can this cause?
When you drink too much water without replenishing electrolytes, causing sodium/electrolyte levels in blood to be lower than normal
can cause confusion, fainting; fatal if misdiagnosed
What are practical hydration goals?
- Getting comfortable with hydration during intensity
- include 250-500ml water with each meal and snack
- consume fluids to match sweat rates or minimize drop in BW (match in vs out)
- monitor for dehydration in heat
- include 500-750ml water or fluids with recovery planning
At what % loss of body weight due to sweating can performance begin to reduce?
As little as 2%
In what type of exercise are adverse effects of dehydration (>2% loss of BW) most severe on?
aerobic endurance performance (especially in hot or humid environments)
What is the difference between voluntary and involuntary water losses?
Voluntary - urination
Involuntary - sweat
Might dehydration and water differ for a trained athlete?
Yes, trained athlete can acclimatize to heat, weather, altitude, etc.
In what situation should fluids be consumed during performance?
when exercise duration exceeds 60min (and when ambient temperature is high) - then fluid deficits during exercise may reach levels that are likely to effect performance
What was the avg. sweat rate of OHL players?
1.4-1.6L/hr
For candidates for Canada’s junior men’s hockey team? What % started hydrated? What was the avg. sweat rate?
What % of sweat loss was replaced?
over 50% started hydrated
avg. sweat rate of 1.8L/hr (goalies - 2.9L/hr)
replaced only 58% of sweat loss
Acute changes in bodyweight are a result of what?
Shift in body water
How can hydration status be estimated?
track early morning bodyweight - measured upon waking after morning pee
What is osmolality?
refers to amount, or concentration, or dissolved substances (solute) in a solution (osmol/Kg solvent)
How does osmolality relate to dehydration and overhydration?
osmolality increases with dehydration (hypertonic) and decreases with overhydration (hypotonic)
number of solute particles per liter of solution
What osmolality value is considered adequate for hydration status?
< 1.020; usually measured upon waking
What tool measures osmolality of pee to check hydration?
Refractometer
How would you do a sweat rate calculation?
1) weigh yourself before workout, record in Kg
2) weigh post workout (Kg)
3) sweat loss in L = bodyweight before - body weight after + fluids consumed during training session
Sweat loss / workout time = sweat rate
What are the limitations with fluid balance assessments?
- results are specific to conditions in which the testing took place (temperature, training status, humidity, intensity/duration, hydration status at start of exercise, acclimatization to environment)
- assumption that 1Kg = 1L - ignored fuel use, CHO oxidation, etc.
Does sweat rate change at intensity increases but duration is the same?
Does sweat rate increase with increased weight of the athlete?
of course
How have the ACSM and NATA recommendations changed for hydration?
Old: athletes should aim to replace 100% of their body weight losses during exercise and to ingest supplemental sodium
New: fluids should be replaced at a rate that will ensure body weight losses
What are the effects of dehydration on exercise performance in research/lab setting?
impaired performance
greater reliance on CHO for fuel
might degrade mental/cognitive performance
impair vigilance (increased errors)
impair reaction time
maybe factor in GI distress
increased RPE
Individual (gender/age differences)
Are the dehydration impacts the same in research and real performance?
performance impact of dehydration is less clear
Describe the variability with % change dehydration at the end of a marathon?
-8% to +5% at the end of a marathon
What are the physiological effects of dehydration?
decreased plasma volume
increased plasma osmolality
increased blood viscosity
decreased central blood volume
decreased filling of the heart
decreased stroke volume
increased HR
decreased cardiac output
decreased skin blood flow
decreased sweat rate
increased core temperature
How does starting a training session in a dehydrated state impact power output?
3.2% drop in mean power output
How does pre-exercise hypohydration of what % of body mass can impair endurance performance?
3% or more of body mass
What is the composition of sweat?
What are the major electrolytes?
99% of sweat is water and 1% is electrolyes
major electrolytes: Na+ and Cl-
What might sodium content of sweat vary according to?
training status, heat acclimatization, hydration status, etc.
Prolonged sweating can cause what % of decreases in electrolytes?
decrease in body Na+ and Cl- by 5-7% and K+ by 1%
How many grams (approx.) are in 1L of sweat at 1.5L/hr sweat rate?
approx. 3.2g Na/L sweat during exercise with sweat rate of 1.5L/hr
What defines exercise-associated hyponatremia?
serum sodium concentration <135mmol/L
Exercise-associated hyponatremia is typically associated with what?
- endurance events (long duration, low intensity)
- increased availability of fluids (before/during) - may need plan or cues
- slower athletes
- lighter bodyweight/smaller individuals/females
What are the signs and symptoms of serum sodium <130mmol/L?
Bloating (GI discomfort)
Puffiness of hands and feet
Nausea
Vomiting
Headache
What are the signs and symptoms of extreme cases of exercise-associated hyponatremia (serum sodium <120mmol/L)?
Seizures
Coma
Respiratory arrest
Permanent brain damage
Death
What are electrolytes?
substance which, in solution, conducts an electrical current
What are the primary electrolytes?
Sodium, chloride, bicarbonate, sulfate, magnesium, calcium
What is the adequate intake for sodium? Are there allowances for increased sodium losses with sweating?
No allowances for increased sodium losses with sweating
1,500mg/day for males & females (9-50yrs) or 1.5g/day
What is the upper limit for sodium?
2,300mg/day or 2.3g/day
What is the Daily Value on food labels set at?
2,400mg/day or 2.4g/day
Should sodium intake/requirement differ for public vs. athlete?
For general public - choosing low sodium often recommended
But for athletes - may need to take in more sodium to replenish their stores (may not look at it the same)
Why does the electrolyte of sodium get the most attention?
there has been no new emerging evidence to suggest that any electrolyte, other than the already identified sodium, has a significant role in hydration before, during, or after exercise.
What is the major function of sodium?
principal electrolyte in ECF, serves to maintain normal body fluid balance & osmotic pressure. Critical for nerve impulse transmission and muscle contraction
also a component to sodium bicarbonate, which helps to maintain normal acid-base balance
Table salt contains what % of sodium? What amount will meet min requirements?
40% sodium in table salt
1tsp = 2.325g Na
What is the function of sodium during intense exercise?
during intense exercise, sodium concentration increases in the blood to maintain blood volume
What is the function of ADH or vasopressin?
increases in ADH/vasopressin helps to conserve body water and Na+ supplies
sodium should be included when sweat losses are high, especially if exercise last more than ____?
2 hrs
What are sodium recommendations for endurance sport before exercise?
foods/fluids containing sodium can help to retain fluids consumed prior to exercise to establish euhydration
What are sodium recommendations for endurance sport during exercise?
440-640mg Na+/L and up to 700-1150mg Na+/L
76-180 K+/L
consume fluids that contain sodium
What are sodium recommendations for endurance sport after exercise?
restoration and replacement of sodium is a prerequisite for an effective restoration and maintenance of euhydration
What are some things an endurance athlete could consume after a 3.5 hr workout?
sports drink
soup/broth
soda crackers and water
chocolate milk (carb, protein, sodium and fluid)
Can fat aid or impede fluid recovery after exercise?
impede fluid recovery
What do current guidelines recommend in terms of excess fluids?
After exercise, what amount should be consumed?
Should no drink in excess of sweating rate
After exercise, approx. 450-675ml of fluid for every pound of body weight lost during exercise;
990-1485ml/kg BW
(or 1-1.5L/kg BW in recovery)
According to ACSM, what amount of water should be consumed before exercise?
What is the result of hyperhydration?
5-7ml/kg BW water or sports beverage at least 4h prior
Hyperhydration will increase the risk of having to void during competition and provides no clear physiologic or performance - practice is discouraged
According to ACSM, what amount of water should be consumed during exercise?
intent to avert a water deficit in excess of 2% of body weight
dependent on individual athlete’s sweat rate, exercise type and duration, and opportunities to drink
individualize
electrolytes to replace sweat loss - Na+ improves thirst and fluid rentention
CHO: 6-8%, duration > 1hr
What is the typical cause of muscle cramping?
muscular fatigue
Can muscle cramping be associated with anything other than muscular fatigue?
Yes - hyper-hydration and electrolyte imbalance
individuals at a higher risk: heavy sweater/high sweat rate; high sweat sodium concentration; not acclimatized to heat and humidity
How can rapid and complete recovery from dehydration be accomplished?
by drinking at least 450-675ml of fluid for every 0.5kg (or 1lb) of body weight lost during exercise
What are environmental impacts on hydration?
cold:
- respiratory losses, sweat losses, clothing inconvenience
altitude:
- diuresis (increased Na+ and water excretion); high respiratory losses; decreases in appetite
humidity:
- impact on sweat rate (increased water content of the air)
What is the best physiological indicator of a subject’s fluid needs during exercise?
thirst
When is moderate consumption of carb-electrolyte solution recommended?
for long duration activity
Why and how you should practice fluid consumption?
individual responses
know sweat rate in variety of training environments - especially if doing 2-day training sessions
