Lecture 9 - Exercise, Fluid balance and Renal Disease Flashcards
What is the function of water in the body?
Transport medium for most body nutrients & gases
• Moistens surfaces for nutrient transfer
• Medium for most waste elimination
• Lubricates joints (water & proteins)
• Gives structure & form to most body structures
• Provides cushioning for many body structures
• Contributes to maintenance of body temperature
Define Dehydration and Rehydration
Dehydration: Process of losing body water, Rehydration: Process of regaining body water to a euhydrated (optimal) state
What %age of water come from fluids, foods and through metabolism?
Flu: 50-60%, Food: 30-40%, Met: 10-15%
What kinds of food contain the most fluid?
Fruit & veg
How do we lose water
Urine: 50-60%, Faces: 5%, Sweat: 5%, Insensible losses from skin and lunges: 30-45%
How many more mL might we lose in hot climates?
NET 3750mL (thru insensible loss)
What infuences body fluid?
Osmolality of fluids via electrolytes (mostly Na+)
What does body fluid mainly affect?
Electrolyte balance, blood volume, arterial blood pressure, cardiac output/blood flow
What is the role of the renal system?
• Formation and excretion of urine
• Regulate blood volume and blood pressure
• Regulate electrolytes
• Stabilize blood pH
• Conserve nutrients
• Excrete waste
• Detoxify poisons
Regulation of body fluids and electrolytes are regulated by which receptors in which parts of the brain?
Osmoreceptors (hypoth.), arterial baroreceptors (mechanoreceptors of the heart), thirst centre/axis (hypoth.)
Name 4 hormones and modulators of the renal axis secreted or controlled by the brain/pituitary
ADH, Aldosterone, ACE, ANP
ADH: a) origin/endocrine gland, b) target tissue, c) mechanism of action, d) stimulators & inhibitors, e) effects or clinical significance
a) post. pituitary, b) collecting duct, c) ADH acts on the collecting duct to increase water reabsorbsion, d) S- osmolreceptors, atrial baroreceptors, thirst centre, angiotensin II. I- ANP , e) inc. water reabsorbsion, decrease urine output, increase atriolar constriction
Angiotensin II: a) origin/endocrine gland, b) target tissue, c) mechanism of action, d) stimulators & inhibitors, e) effects or clinical significance
a) precursor: angiotensin which originates from the liver, b) blood vessels, arenals, kidneys, brain, c) A-II causes vasoconstriction (BV), secrets aldosterone (Adr), enchances sodium reabsorbsion (Kid), acts on the thirst centre (Bra), d) S- mainly renin via the RAAS. I- -ve feedback, ANP, inc. BP and BV, ACE inhibitors, e) increase thirst, vasoconstriction, increases ADH release, increase aldosterone release
Aldosterone: a) origin/endocrine gland, b) target tissue, c) mechanism of action, d) stimulators & inhibitors, e) effects or clinical significance
a) adrenals, b) kidneys c) promotes Na2+ reabsorbsion d) S- mainly renin via the RAAS, hyperkalemia, hypoatremia, I-ANP, increase BP, cortisol
Renin: a) origin/endocrine gland, b) target tissue, c) mechanism of action, d) stimulators & inhibitors, e) effects or clinical significance
a) kidneys, b) angiotensin c) catalyses the conversion of angiotensin to angiotensin-I d) S- decreased BP, stress (SNS), reduced NaCl infiltrate, I- Angiotensin-II, increased BP an BV
ANP: a) origin/endocrine gland, b) target tissue, c) mechanism of action, d) stimulators & inhibitors, e) effects or clinical significance
a) heart b) kidneys, adrenal glands, and blood vessels, c) promote inhibition of sodium and water reabsorption in the kidneys, d) S- increased atrial pressure and volume expansion, I- SNS activation and angiotensin II, e) vasodilation, reduction in blood volume, and blood pressure regulation, as well as antagonism of the renin-angiotensin-aldosterone system.
What are the steps in the RAAS?
Decreased blood pressure or sodium –>
Renin secretion from kidney –>
Renin converts angiotensinogen to angiotensin I –>
ACE in lungs converts angiotensin I to angiotensin II –>
Angiotensin II stimulates adrenal cortex to release aldosterone –>
Aldosterone acts on kidneys to increase sodium reabsorption and potassium excretion.
What initiates renin release and activates the RAAS system? (i.e.: what is the stimulus?)
decreased blood pressure and decrease sodium in the body (at the kidneys)
what are the biochemical effects of ANP
– Blocks release of ADH
– Blocks release of aldosterone
– Blocks Na + reabsorption in kidneys
– Reduces sympathetic cardiac drive: decreases arterial BP
What happens to BP and BV during the onset of exercise? What is the mechanism?
NET DECREASE. BP & BV drop as you start sweating (lose fluid and electrolytes). Metabolites rise, osmolality and osmotic pressure increase in RBCs and water in interstitial spaces like the blood vessels decrease. This stimulates osmolreceptors in the brain which begin a compensatory mechanism
What happens to BP and BV during exercise, after onset? What is the mechanism?
NET INCREASE. To compensate for a decrease in BP and BV, cardiac output increase and vasoconstriction occur. This is due to increases in ADH and activation of the RAAS system as well as a decrease of ANP secretion
What happens to BP and BV during prolonged exercise in the absence of rehydration? What are the consequences?
BP and BV slowly decrease due to loss of fluids and electrolytes in sweat and for metabolic processes. Conseq.: decreased BV, compramised cardiac output and blood pressure.
Name some physiological responces to exercise
• Increase sodium reabsorption
• Increase water reabsorption
• Decrease urine output
• Increase plasma volume
What are some of the effects of repeated days of activity on the renal system?
• Increased release of fluid balance hormones
• Increased plasma volume
How would you prevent dehydration pre-exercise and ensure re-hydration post exercise?
PRE • Ensure at least euhydration pre-exercise
POST • Weigh before & after exercise
– Consume fluid to volume lost plus 25%
• Ensure urine colour returns to pale yellow
When would you especially need to hydrate during exercise?
Hydrate during exercise if:
– Long duration
– High ambient temperature
– High humidity
If you need to rehydrate quickly during exercise, what is it best to consume?
• Consume a cool sports drink if rate of rehydration is important (water and electrolytes)
– Hypotonic (relative to blood) and w/o glucose as this will act against the osmolality of solutes, drawing water out of the bloodstream
What is hyponaturemia and when might it occur?
Low salt/water intoxication - Serum Na < 136 meq/L (150 normal), prolonged sweating & excess plain water intake
What are some symptoms of hyponaturemia?
Mild symptoms - Headache, confusion, nausea, cramps
Severe symptoms - Seizures, coma, pulmonary oedema, death
Who is most at risk of hyponaturemia?
Ultra-endurance athletes, people less accustomed to prolonged exercise, Consume a low salt diet, diauretic medications, large quanities of plain water
What is the prevention of hyponatremia
No more than 1 L plain water per hour during or after exercise
• Add some sodium & glucose to drinks
• Sprinkle salt on food in days prior to (and following) exposure
What are the main risk-factors of kidney disease?
Diabeties and hypertension
What can cause acute kidney injury?
Pre and Intra-Renal: factors that reduce blood flow to kidneys like dehydration, blood loss, lower BP, heart failure. Also: drugs (nephrotoxicity), acute tubular necrosis. Post-renal causes: kidneys stones, tumors, enlarged prostate
What can cause Chronic Kidney Disease?
Diabeties, high blood pressure (hypertension), Glomerulonephritis, Polycystic Kidney Disease, prolonged obstruction of the urinary tract, repeat kidney infection
What happens to aerobic capacities in people with kidney disease
Very low aerobic capacities (VO 2max)
What sorts of tests are relevant with people with kidney disease?
Fitness tests may use lower level activities:
– ADLS
– Stair climbing
– 6 min walk test
What are the considerations of exercise testing for people at: State 1-4 and Stage 5 kidney disease?
• Stages 1-4 – usual considerations
• Transplant - usual considerations
• Stage 5 – requires medical supervision
• Hemodialysis – test on non-dialysis days
• Peritoneal – test when no fluid in abdomen
What sorts of strength tests are relevant with people with kidney disease?
• 3RM or more (not 1RM)
• Isokinetic – slower velocities (60-180 deg/s)
• Sit to stands
What are the standard considerations in aerobic training recommendations for people with kidney disease?
– Low-mod intensity activities (walk, swim, cycle)
• 40-60% max, then progress if can
– As many days as possible
– RPE 11-13 (HR is poor indicator)
• Non-dialysis days = RPE 11-16
– Begin with intermittent (interval) activity
– Progress to continuous activity
– Aim for 30-45 min continuous
• Longer if overweight/obese
What are the standard considerations in anaerobic training recommendations for people with kidney disease?
Strength training
– Aim to increase or maintain muscle mass
– 1 set of 10-15 reps to fatigue
– 8-12 exercises targeting major muscle groups
– 2 x week (non-consecutive days)
– Motivation often difficult
What should be considered regarding the timing of exercise around dialysis (pre-, during-, post-, and non-dialysis days)?
• Pre dialysis:
– Fluid load problems (e.g., breathlessness)
• Post dialysis: (issue is fluid loss)
– Don’t train immediately post dialysis
• During dialysis:
– Possible during first 2 hours of dialysis e.g., cycling
• Non-dialysis days:
– Exercise usually better tolerated
