PT 663 Exam 1 (monday)

PA aerobic guidelines for children and adolescents 11-17yrs old

• 60 minutes or more of moderate to vigorously intense PA daily

  • vigorous activity, muscle strengthening activities, high impact activities at least 3x a week

• variety of enjoyable activities

PA aerobic guidelines for adults 18-64yrs

• at least 150 minutes a week of moderate intensity activity

• or 75 minutes of vigorous intensity activity

• 2x a week of strengthening

PA aerobic guidelines for older adults 65yrs and older

• at least 150 min/week of moderate intensity

• or 75 min/week of vigorous

• at least 2x strengthening

• improve balance

PA recommendations on frequency

moderate

• 5x/week

vigorous

• at least 3x a week

or combination of the two

what is a MET?

used to determine the amount of energy expenditure/the intensity of an exercise

• absolute measure of intensity

describe the intensity of <3.0 METS

light exercise

• slow walking

• sitting

• standing - light work

• fishing

describe the intensity of 3.0-6.0 METS

moderate intensity

• brisk walking (4mph)

• cleaning - heavy

• mowing lawn

• bicycling - light

• badminton

describe the intensity of 6.0 METS

vigorous PA

• intense walking/hiking

• jogging (6mph)

• shoveling

• carrying heavy loads

• fast cycling

• basketball game

• soccer game

what is the Borg scale?

a scale for the rate of perceived exertion (RPE)

• Original Borg = 6-20

• modified Borg = 0-10

works well with patients to understand how hard they are working

how does the Borg scale correlate to METs?

moderate: 3-5.9 METs

• 5 or 6 on RPE

• 30-60 min/day or 150-300 min/week

vigorous: > 6 METs

• relative 7 or 8 on RPE

• 75-100 min/week

how should PA guidelines be applied for people who are insufficiently active

• both decrease sedentary behavior and moderate/vigorous PA

how should PA guidelines be applied for people who are inactive?

• focus on decreasing sedentary behavior

• gradually increase PA

what is the minimum frequency aerobic training should be prescribed?

• minimum 2x/week

• benefits within 8-12 weeks

what is the minimum intensity aerobic training should be prescribed?

• 60-90% HR max

• 50-85% HRR or VO2max

  • 50-65% = moderate

  • 65-85% = vigorous

What is HR max

220 - age (percentage) = age predicted HR

• 60-60%

what is HRR?

HR max - HRrest

• (HR max - HRrest) x% + HRrest

for intensity, is HR reserve or HR max preferred?

HR reserve

• most closely relates to VO2 max (work capacity)

what is VO2max?

measurement of aerobic capacity

what factors affect VO2max?

mode: exercises using larger muscle groups

age: decrease with age

sex: men > women

body size: larger/muscle mass > smaller

hereditary: 20-30%

how should intensity be tracked for patients on beta-blockers?

• should use RPE

• due to the beta blockers working to slow the heart

what is the recommended time for exercise prescription?

minimum of 10 min/session, but overall goal is at least 30 min/session

what is the difference in intensity for UE and LE exercises

• UE exercises have a higher intensity for the same workload, but reaches a maximum sooner

• smaller muscle groups have less mechanical and myocardial efficiency

what is continuous training?

build to overload to complete goal

• light start and gradual increase until steady state is met

• the original start is the oxygen deficit

interval training for aerobic benefits

work interval/recovery interval should be 1:1 or 1:1.5

• activity does NOT stop → it should be high intensity/low intensity

• want average HR to be in zone

what is cardiac output?

CO = HR x SV

• L/min

how does exercise impact CO?

• increases overall CO

• redistributes it to increase the input to muscles (flow)

function of the cardiovascular system

deliver materials throughout the body to meet metabolic needs

how is the flow of cardiac output found?

Q = ΔP/R

• ΔP: pressure gradient

• R = resistance

how are increased metabolic demands met?

• increased CO

• increased Q (flow)

what is resting vs high intensity CO?

Resting: ~5 L/min

Exercising: ~25 L/min

what signal causes the heart to beat?

change in membrane potential

• resting: -90mV (high K+ in cell, more Na+ and Ca++ outside of cell)

• depolarize: Na+ rushes in and increases charge

describe the AP in cardiac tissue

• Na+ rushes in to depolarize

• Na+ gates opening is short, which causes a spike

• Depolarization triggers Ca2+ channels to open, which keep charge up

• K+ open at same time, which keeps charge steady

• Eventually Ca2+ close and K+ rushing out repolarizes membrane

what is nodal tissue

specialized myocytes to be the pacemakers of the cardiovascular system

• resting membrane potential not steady, increases due to Na+ and Ca2+ opening regularly

• depolarizes until threshold is met and AP occurs

what is automaticity important for in the CV system?

• due to unstable resting potential, AP are triggered regularly within the hear without control from the CNS

what are the nodes where the nodal cells cluster?

• SA node

• AV node

• Bundle of His, Bundle branches, and Purkinje fibers

(in order of fastest to slowest intrinsic rate)

how do the nodes in the heart operate to control HR?

Overdrive suppression by the SA node

• since the intrinsic rate of the SA node is higher

• (if there are active APs from the SA node at a faster rate, it does not allow the time for the other nodes to contract on their own)

what does the p wave represent?

depolarization of SA node and ventricles

what does the QRS complex represent?

depolarization of the ventricles

what does the T wave represent?

repolarization of the ventricles

What occurs during contraction/systole of heart muscle

1. Ca²⁺ influx during AP (interacts with RyR)

2. Ca²⁺ release from SR

3. Ca²⁺ binds to troponin, exposing binding site on actin

4. myosin-actin cross-bridge formation and contraction

what occurs during relaxation/diastole of the heart?

1. Ca²⁺ removed from sarcoplasm via

   1. SERCA pump and

   2. Ca²⁺ and Na-Ca exchanger

2. Ca²⁺ leaves troponin, blocking actin-myosin interaction and preventing contraction

measurements gained from an ECHO

• end systolic volume (ESV) - volume in the chamber

  • should be relatively small

• end diastolic volume (EDV)

  • should be smaller

• Stroke volume (SV)

• Ejection fraction (EF)

what is stroke volume?

SV = EDV - ESV

what is ejection fraction?

EF = SV/EDV

• normal ~50-75%

describe the cardiac cycle of the heart

1. Ventricular and atrial diastole

2. Atrial systole and ventricular diastole

3. Isovolumic ventricular contraction and atrial diastole

4. Ventricular systole and atrial diastole

5. Isovolumic ventricular relaxation

what occurs during isovolumic contraction?

• building of pressure but no contraction/pushing

• pressure has to overcome valves before opening

what is a positive chronotropic effect? negative?

• positive = an increasing HR

• negative = a decreasing HR

what controls a positive chronotropic effect?

sympathetic activation

• norepinephrine acts on Beta-1 receptors in the SA node

what controls a negative chronotropic effect?

parasympathetic activation

• ACh released from vagus nerve acts on muscarinic receptors

how does HR and stroke volume relate?

as HR increases → SV decreases

• decreased duration of diastole

• decreased time for ventricular filling

correlation of HR and CO

as HR increases, there is an initial increase in CO, then a decrease

• to increase CO, increase in HR must be accompanied by increased ventricular filling (vasocontriction and muscle pump)

what 3 factors impact stroke volume?

preload

• volume of blood in ventricles at end of diastole (measure of stretch)

• larger = larger SV

afterload

• resistance ventricle must overcome to eject blood

• related to BP

• Increased after load = decreased SV

  • for same amount of effort, less blood ejected

contractility

• how hard the heart is beating

• strength of contraction

• increase = increased SV

how does preload impact SV?

greater EDV → greater stretch on myocyte

• primes it for contraction by pulling it to the optimal sarcomere length

• allows for a stronger contraction → larger SV

affected by

• blood volume

• venous return

• length of diastole

how does after load impact SV?

pressure ventricles must overcome to eject into aorta

• decreased = more SV

  • hypotension

• increased = less SV

  • hypertension, aortic stenosis

how does contractility/inotropy impact SV?

Ca²⁺ dependent strength of the beat

• + inotropy:

  • increased calcium concentration

  • more cross bridge formation

  • stronger contraction

  • greater SV

• - inotropy:

  • decreased calcium concentration

  • less cross bridge formation

  • weaker contraction

  • weaker SV

controlled by sympathetic nervous system

what is the measurement of oxygen consumption?

VO₂ = CO x (Ca_O2 - Cv_O2)

• CO = cardiac output

• a = arterial blood oxygen content

• v = venous blood oxygen content

• work rate and oxygen consumption have a relatively linear relationship

what increases CO physiologically?

increased SV

• positive inotropy via sympathetic stimulation

• increased preload due to increased venous return

increased HR due to

• parasympathetic withdrawal

• sympathetic stimulation of SA node

what are muscle pumps?

muscular components assisting in venous return of blood to the heart

• contracted muscles squeeze veins (valves prevent backflow)

why is an increase HR alone not responsible for an increase in CO?

a high HR decreases diastole → decreases the filling → decreases stroke volume

how does exercise impact the muscle pumps?

• increases the amount of blood returning to heart (more muscle use)

• rapid/deep breathing improves respiratory muscle pump

  • inhalation: decreased thoracic pressure and increased abdominal pressure → blood goes to thorax

  • exhalation: thoracic pressure increased and abdominal pressure decreased → pushes blood from legs into abdomen + thorax into heart

what does the oxygen supply to the heart depend on?

• arterial O2 content

• coronary blood flow

what does the oxygen demand to the heart depend on?

• HR

• factors impacting CO (afterload, preload, contractility)

what is rate pressure product?

myocardial O2 demand

• RPP = HR x SBP (systolic blood pressure)

• best clinical measure we have of demand

• beneficial to use for those with CAD to prescribe exercise and avoid ischemia

how do the coronary arteries flow?

flow to blood during diastole

• Wall is expanded = vessels dilate

• in exercise HR is increased → O2 demand increased → but more contraction = less diastole and less time for oxygen to reach tissues

how does the sympathetic and parasympathetic systems regulate HR?

sympathetic:

• Norepinephrine

• acts on Beta-1 receptors in SA node

• increases inotropy

parasympathetic:

• ACh released from vagus nerve

• acts on muscarinic receptors

how does flow and CO overlap?

Q = ΔP/R

• Q = cardiac output (CO)

• ΔP = mean arterial pressure (MAP)

• R = total peripheral resistance

what are the greatest source of resistance to flow in the cardiovascular system?

arterioles

• a large pressure drop to begging to end of arterioles

• if pressure drops and flow is the same → resistance is increased

what are the important functions of arterioles

• critical for maintenance of blood pressure and distribution of blood flow

what is mean arterial pressure?

average pressure in vessels

• since diastolic is longer than systolic, it is not simply the difference between the two, therefore it is lwoer