Hypertension and ExerciseHypertension and Exercise

due to hardening of arteries, excessive due to hardening of arteries, excessive peripheral resistance (enhanced nervous peripheral resistance (enhanced nervous tone or kidney malfunction)tone or kidney malfunction)

pressures of 250-300 for systole and >90 pressures of 250-300 for systole and >90 mm Hg for diastolemm Hg for diastole

aerobic exercise can modestly lower BP aerobic exercise can modestly lower BP extent is unclear, but beneficial for extent is unclear, but beneficial for

normotensive and hypertensive individualsnormotensive and hypertensive individuals

resting BP also lowers significantly, resting BP also lowers significantly, possibly due to higher circulating possibly due to higher circulating catecholamines after training catecholamines after training decreased decreased peripheral resistance to blood flow, peripheral resistance to blood flow, decreasing BPdecreasing BP

exercise may enhance sodium elimination exercise may enhance sodium elimination by kidneysby kidneys

BP and ExerciseBP and Exercise

static and dynamic resistance exercise will static and dynamic resistance exercise will increase peripheral resistance to BFincrease peripheral resistance to BF

even at light loads, e.g., 25% 1RMeven at light loads, e.g., 25% 1RM potential for harm for those with heart and potential for harm for those with heart and

vascular disease vascular disease chronic resistance training does not chronic resistance training does not

appear to increase resting BP, and can appear to increase resting BP, and can blunt the response to a single boutblunt the response to a single bout

Steady State exerciseSteady State exercise

dilation of blood vessels in working dilation of blood vessels in working muscles will decrease TPR, increase BF muscles will decrease TPR, increase BF to working muscleto working muscle

may see a small rise in systole, 140-160 may see a small rise in systole, 140-160 mm Hg, then levels offmm Hg, then levels off

diastole may increase or decrease 10 mm diastole may increase or decrease 10 mm Hg, or remain unchangedHg, or remain unchanged

Graded ExerciseGraded Exercise

Increase in systole, mean, and diastole Increase in systole, mean, and diastole with increase in Qwith increase in Q

greatest changes are in systole, diastole greatest changes are in systole, diastole may change only ~12%may change only ~12%

Arm ExerciseArm Exercise

systole and diastole significantly higher systole and diastole significantly higher than with leg exercise, even at same than with leg exercise, even at same intensityintensity

may be due to smaller vasculature, may be due to smaller vasculature, increased resistance to flowincreased resistance to flow

heart will have to work harderheart will have to work harder

RecoveryRecovery

after submax exercise, systolic pressure after submax exercise, systolic pressure can be temporarily (2-3 hrs) depressed can be temporarily (2-3 hrs) depressed below pre-exercise levelsbelow pre-exercise levels

B/c TPR remains low after exerciseB/c TPR remains low after exercise

Heart Blood SupplyHeart Blood Supply

has its own blood supplyhas its own blood supply has dense capillary network has dense capillary network @ rest, normal BF to myocardium is ~200-@ rest, normal BF to myocardium is ~200-

250 ml, 5% of Q250 ml, 5% of Q

Myocardial oxygen utilizationMyocardial oxygen utilization

@ rest, 70-80% of oxygen is extracted @ rest, 70-80% of oxygen is extracted from the blood in coronary vesselsfrom the blood in coronary vessels

in other tissues, @rest, ~25% of the in other tissues, @rest, ~25% of the oxygen is extractedoxygen is extracted

coronary BF will increase during exercise coronary BF will increase during exercise to meet myocardial oxygen requirements, to meet myocardial oxygen requirements, can increase 4-6X above resting levelscan increase 4-6X above resting levels

Two ways to increase myocardial Two ways to increase myocardial BFBF

1. Increased myocardial metabolism causes 1. Increased myocardial metabolism causes dilation of coronary vesselsdilation of coronary vessels

2. Increased aortic pressure forces a larger 2. Increased aortic pressure forces a larger amount of blood into coronary circulationamount of blood into coronary circulation

coronary BF is 2.5X greater during diastole than coronary BF is 2.5X greater during diastole than during systoleduring systole

heart has limited ability to generate energy heart has limited ability to generate energy anaerobicallyanaerobically

Myocardial MetabolismMyocardial Metabolism

has a 3X higher oxidative capacity than has a 3X higher oxidative capacity than skeletal muscleskeletal muscle

have the greatest mitochondrial density, have the greatest mitochondrial density, well adapted for fat catabolism as primary well adapted for fat catabolism as primary source of ATP resynthesissource of ATP resynthesis

Figure 15-9 this is the substrate use of the Figure 15-9 this is the substrate use of the heart at rest, during exercise, and during heart at rest, during exercise, and during recoveryrecovery

glucose, fatty acids, and lactate provide glucose, fatty acids, and lactate provide energy for the heartenergy for the heart

during heavy exercise, with a large during heavy exercise, with a large concentration of lactic acid in the blood, the concentration of lactic acid in the blood, the heart can use lactate for 50% of its total heart can use lactate for 50% of its total energyenergy

during prolonged submax activity, 70% of during prolonged submax activity, 70% of energy comes from fatty acidsenergy comes from fatty acids

metabolic patterns are similar for TR and metabolic patterns are similar for TR and UNTR, but TR have a greater contribution of UNTR, but TR have a greater contribution of fats to the total energy requirementfats to the total energy requirement

Rate-Pressure Product: Rate-Pressure Product: Estimate of myocardial workEstimate of myocardial work

increase in myocardial contractility and heart increase in myocardial contractility and heart rate will increase the demand for oxygenrate will increase the demand for oxygen

estimate myocardial workload and oxygen estimate myocardial workload and oxygen consumption, use product of peak systole consumption, use product of peak systole and heart rateand heart rate

index of relative cardiac workindex of relative cardiac work

called the double product, or rate-pressure called the double product, or rate-pressure productproduct

highly related to myocardial oxygen consumption highly related to myocardial oxygen consumption and coronary BFand coronary BF

RPP = SBP X HRRPP = SBP X HR with training in cardiac patients, a higher RPP with training in cardiac patients, a higher RPP

can be achieved before ischemic symptoms can be achieved before ischemic symptoms appearappear

this measure is used in coronary heart disease this measure is used in coronary heart disease patientspatients

Blood DistributionBlood Distribution

rapid adjustments are necessary during rapid adjustments are necessary during exercise, possible by constriction and dilation exercise, possible by constriction and dilation of smooth muscular bands of arteriolesof smooth muscular bands of arterioles

additionally, venous capacitance vessels additionally, venous capacitance vessels stiffenstiffen

can rapidly redistribute blood to meet can rapidly redistribute blood to meet metabolic demand of exercise, while metabolic demand of exercise, while preserving adequate flow and pressure preserving adequate flow and pressure throughout the systemthroughout the system

Regulation of Blood FlowRegulation of Blood Flow

changing diameter of blood vessels is changing diameter of blood vessels is most important factor regulating regional most important factor regulating regional flowflow

resistance to flow changes with vessel resistance to flow changes with vessel diameter (to the fourth power)diameter (to the fourth power)

reducing diameter by 1/2, causes flow to reducing diameter by 1/2, causes flow to decrease 16Xdecrease 16X

Local FactorsLocal Factors

1 in 30-40 capillaries is open at rest1 in 30-40 capillaries is open at rest

opening capillaries during exercise willopening capillaries during exercise will

1. Increase muscle blood flow1. Increase muscle blood flow

2. Due to the increase in channels, 2. Due to the increase in channels, increased blood volume can be delivered increased blood volume can be delivered with only small increases in velocity of flowwith only small increases in velocity of flow

3. Enhanced vascularization will increased 3. Enhanced vascularization will increased the effective surface for exchange the effective surface for exchange between blood and muscle cellsbetween blood and muscle cells

local factors can increase the dilation of local factors can increase the dilation of arterioles and precapillary sphinchtersarterioles and precapillary sphinchters

Local FactorsLocal Factors

1. Decrease in oxygen supply1. Decrease in oxygen supply

2. Increase in temperature2. Increase in temperature

3. increase in carbon dioxide3. increase in carbon dioxide

4. increase in acidity4. increase in acidity

5. increase in adenosine5. increase in adenosine

6. increase in ions of magnesium and potassium6. increase in ions of magnesium and potassium these are autoregulatory mechanismsthese are autoregulatory mechanisms

Neural factorsNeural factors

sympathetic and to small extent, sympathetic and to small extent, parasympathetic portions of autonomic NS parasympathetic portions of autonomic NS provide a central vascular controlprovide a central vascular control

muscles contain sensory nerve fibers which are muscles contain sensory nerve fibers which are sensitive to substances released in local tissue sensitive to substances released in local tissue during exercise: causes vascular responsesduring exercise: causes vascular responses

central regulation ensures that the area with the central regulation ensures that the area with the most need for oxygen gets the most blood flowmost need for oxygen gets the most blood flow

norepinephrine is the general norepinephrine is the general vasoconstrictor, and is released at vasoconstrictor, and is released at certain sympathetic nerve fibers certain sympathetic nerve fibers (adrenergic fibers)(adrenergic fibers)

other sympathetic fibers can release other sympathetic fibers can release ACH, causing vasodilation (cholinergic ACH, causing vasodilation (cholinergic fibers)fibers)

dilation of blood vessels is due more to dilation of blood vessels is due more to a reduction in vasomotor tone than to a reduction in vasomotor tone than to an increase in action of either an increase in action of either sympathetic or parasympathetic dilator sympathetic or parasympathetic dilator fibersfibers

Hormonal FactorsHormonal Factors

sympathetic nerves terminate in the sympathetic nerves terminate in the medullary portion of the adrenal glandmedullary portion of the adrenal gland

with activation, epi is released in large with activation, epi is released in large quantities, norepi in small quantitiesquantities, norepi in small quantities

epi and norepi cause a constrictor epi and norepi cause a constrictor response, except in blood vessels of the response, except in blood vessels of the heart an skeletal muscleheart an skeletal muscle

during exercise, hormonal control is minor during exercise, hormonal control is minor in the control of regional BFin the control of regional BF

BF is decreased to the skin, gut, spleen, BF is decreased to the skin, gut, spleen, liver, and kidneys as a general responseliver, and kidneys as a general response

Integrated Response in Integrated Response in ExerciseExercise

Nerve centers above the medullary region Nerve centers above the medullary region are active both before and at the onset of are active both before and at the onset of exercise to cause increases in the rate exercise to cause increases in the rate and contractility of the heart, as well as to and contractility of the heart, as well as to change regional blood flowchange regional blood flow

sympathetic cholinergic outflow plus local sympathetic cholinergic outflow plus local metabolic factors acting on metabolic factors acting on chemosensitive nerves and on blood chemosensitive nerves and on blood vessels cause dilation in active musclesvessels cause dilation in active muscles

this reduces peripheral resistance, this reduces peripheral resistance, allowing for greater blood flowallowing for greater blood flow

constriction adjustments will then occur constriction adjustments will then occur in less active tissues as exercise in less active tissues as exercise continues, so that perfusion pressure continues, so that perfusion pressure can be eliminatedcan be eliminated

factors influencing venous return:factors influencing venous return:1. action of muscle and ventilatory pumps1. action of muscle and ventilatory pumps2. stiffening of the veins2. stiffening of the veins3. increase in venous tone with an 3. increase in venous tone with an

increase in Qincrease in Q

Cardiac OutputCardiac Output

Q = HR X SVQ = HR X SV primary indicator of the functional capacity primary indicator of the functional capacity

of the circulation to meet the demands of of the circulation to meet the demands of PAPA

Four methods to determine Q:Four methods to determine Q:

Direct FickDirect Fick Q = OQ = O22 consumed/ (a-v)O consumed/ (a-v)O22 Indicator Indicator

Dilution: examine an indicator dilution Dilution: examine an indicator dilution curvecurve

COCO22 rebreathing, indirect Fick rebreathing, indirect Fick Q = COQ = CO22 production/ (v-a)CO production/ (v-a)CO22 X 100 X 100

ImpedanceImpedance SVSV PreloadPreload AfterloadAfterload ContractilityContractility BPBP Systemic Vascular Resistance (SVR)Systemic Vascular Resistance (SVR) Can index the values to body sizeCan index the values to body size