Fluid, Electrolytes, And Exercise Flashcards
What is water’s role in the body?
Solvent, Solute, Reactant, Product, Carrier, Lubricant, Shock absorber, Coolant, Catalyst, Ionizing agent, Messenger, Controller
What are water’s unique properties?
High heat capacity
High thermal conductivity
The above 2 help keep the body from overheating
High latent heat of evaporation
In thermoneutral conditions, what is body fluid balanced maintained at?
0.2% of total body weight
How is fluid lost?
Urine, feces, sweat, respiration, and transcutaneous water loss
What 2 receptors help maintain hydration?
Hypothalamic osmoreceptors - gauge the osmolality of the blood
Vascular baroreceptors - gauge the pressure within major vessels
What is osmolality?
Concentration of particles dissolved in fluid
High - dehydration
Normal - euhydration
Low - overhydration
What is vasopressin?
Antidiuretic hormone - increases water reabsorption
Where is vasopressin released from?
Pituitary gland
What does renin do and where is it released from?
Controls the production of aldosterone
Kidneys
What does aldosterone do?
Helps manage blood pressure
Retains sodium
Loses potassium
What is angiotensin II?
Helps regulate blood pressure by constricting (narrowing) blood vessels
Triggers sensation of thirst and desire for salt intake via hypothalamus
Stimulates release of vasopressin
Factors that affect fluid status
Body size
Body composition
Physical activity
Environmental (temperature, altitude, humidity)
What is the DRI recommendations for water intake?
Males - 3.7 L/day (130 oz) or 16 cups
Females - 2.7 L/day (95 oz) or 12 cups
What is the daily percentage of fluid consumed by food and beverages?
Food - 20%
Beverages - 80%
What two minerals are found in the greatest concentration of sweat?
Sodium and chloride
Symptom of large salt losses in sweat
Dry, white residue on the skin and clothing after sweat dries
Health risks of large sodium chloride losses
Heat-related problems
Hyponatremia
Muscle cramps
Hydration recommendations pre exercise
Both answers
5-10 ml/kg of body weight 2-4 hours before
OR
2 hours before: 16-24 oz
15 minutes before: 8-16 oz
Hydration recommendations during exercise:
General
High intensity (30-75 minutes)
Endurance and intermittent, high intensity (1-2 hours)
Endurance (2-3 hours)
Endurance (>/=) 2.5 hours)
Typically depends on sweat rate
General guideline: 0.4-0.8 L/hr
High intensity (30-75 minutes): 6-12 oz of water every 15 minutes (plus carbs and electrolytes as needed)
Endurance and intermittent, high intensity (1-2 hours): 6-12 oz of water every 15 minutes plus carbs (and electrolytes as needed)
Endurance (2-3 hours): 6-12 oz of water every 15 minutes plus carbs (and electrolytes as needed)
Endurance (>/=) 2.5 hours): 6-12 oz of water every 15 minutes plus carbs (and electrolytes as needed; may also be beneficial to add small amounts of protein)
Hydration recommendations after exercise
Drink 1.25-1.5 L for every 1 kg of body weight lost
Benefits of adequate fluid intake on heart rate, stroke volume, cardiac output, skin blood flow, core temperature, perceived exertion, performance
Heart rate Lower
Stroke volume Higher
Cardiac output Higher
Skin blood flow Higher
Core temperature Lower
Perceived exertion Lower
Performance Better
What is the most biologically active molecule in the body
Water
An appetite for what minerals exist
Sodium chloride, but not for any other minerals
What percent of body weight change is considered excessive regarding hydration status
> 2%
What sweat glands are responsible for secreting sweat during exercise and heat exposure and are part of the thermoregulatory response
Eccrine
Total volume of fluid loss is based on
Environmental conditions
Size (surface area) of individual
Metabolic rate
Physical activity
Sweat loss
Composition of diet
Volume of excreted fluids
Why is water loss high during cold temperatures
The air inhaled during cold weather activity contains relatively little water vapor, so as it is warmed and humidified during its transit through the respiratory tract, additional water loss occurs
What is the minimum daily water need for a completely sedentary individual and what is the requirement in most minimally active individuals
Sedentary: No less than 1 L/day
Minimally active: 3-4 L/day
Average water loss per hour of most athletes
1-2 L/hr
Ingesting an extra 3g of sodium requires how much additional fluid intake
1 L
How much water is required to excrete the urea produced from 100 G protein
700 mL
How much fluid is required to oxidize 100 kcal of carbs, protein, and fat
Carbs: 15 mls
Protein: 13 mls
Fat: 9 mls
Three reasons why thirst is an unreliable regulator of fluid needs during exercise
Behavioral - signals can be easily missed or disregarded due to distractions
Fluid may not be readily available
Physiological - osmolality must reach a certain point to trigger thirst
What is the average level of thirst threshold for people
290-295 mOsm/kg
How much sweat needs to be lost for electrolyte intake to become important
Greater 4 L
Sensation of thirst is a function of what
Changes in plasma sodium concentrations (plasma osmolality) and of changes in blood volume
Drinking plain water removes the osmotic drive to drink (by quickly diluting the sodium concentration of the blood) and reduces the volume dependent drive (by partially restoring blood volume), causing the premature satiation of thirst
Plasma sodium decreases
Blood volume increases
Why is it unwise to recommend glycerol induced hydration
Athletes pay a metabolic cost for carrying around extra weight
No compelling evidence it causes any physiological benefit
Side effects
Can possibly cause hyponatremia
Banned for the World Anti-Doping Agency (may mask doping)
Why to avoid consuming a sports drink that contains more than 6-7% carbohydrates
Decrease the rate of gastric emptying
Decreases the rate of fluid absorption
How much sodium is lost per hour during exercise
50 mEq/L or 1 g/hr
List the added benefits of consuming sodium in a rehydration drink
Stimulating athletes to drink more
Palatability
Reduces urination to help maintain blood volume
List the several different mechanisms of cooling and which ones are more prevalent in adults and children
Radiation, Evaporative, Conductive, and Convective
Adults: evaporative/sweating
Children: radiative and conductive
At what temperature is fluid most lost from urine or sweat
Urine: 68F
Sweat: 85F
What is the amount of weight lost and physical effect of the below dehydration percentages
1%
3%
5%
7%
10%
1.5# - increased body temperature
4.5# - impaired performance
7.5# - GI problems, Heat exhaustion
10.5# - hallucinations
15# - circulatory collapse
Losing more than 2% of body weight from dehydration may result in
Early fatigue
Difficulty making decisions
Difficulty determining the best play
Difficulty communicating with teammates
Why would an athlete’s fluid needs be increased in altitude training
Increase diuresis
Expanding blood volume
How often should a well hydrated athlete urinate daily
Every 2-4 hours
Typical sports drink breakdown
15 g carbs/8 oz
110 mg/8 oz
Negative effects of consuming alcohol
Diuretic
At risk for dehydration, heat illness, and cramping
Suppresses fat use as a fuel during exercise
Interferes with post-exercise recovery by delaying carb repletion and muscle recovery
Increases risk for micronutrient deficiencies and adds empty calories
Decreases restful and restorative sleep
What are the fluid, carbohydrate, electrolyte, and protein recommendations for the below activities
High intensity activity (30-75 minutes)
Endurance and intermittent, high intensity (1-2 hours)
Endurance (2-3 hours)
Endurance (>/= 2.5 hours)
High intensity activity (30-75 minutes): 6-12 oz/15 minutes (plus carbs and electrolytes as needed when > 1 hour)
Endurance and intermittent, high intensity (1-2 hours): 6-12 oz/15 minutes plus carbs (and electrolytes as needed)
Endurance (2-3 hours): 6-12 oz/15 minutes plus carbs (and electrolytes as needed)
Endurance (>/= 2.5 hours): 6-12 oz/15 minutes plus carbs (and electrolytes as needed; may also benefit to add small amounts of protein)
