cardiovascular system and exercise. cardiac output amt. of blood pumped by heart in 1 - minute hr x...

Cardiovascular System and Exercise

Cardiac Output Amt. of blood pumped by heart in

1 -minute

HR x SV

Measuring Cardiac Output Fick Method

Indicator Dilution

Thermal Dilution

CO2 Rebreathing

Direct Fick Method 02 consumption spirometry

Arterial blood ABG

Mixed venous blood catheter

Direct Fick Method

Direct Fick Method

O2 consumption (mL/min) x 100

a-v O2 difference (mL/100 mL blood)

Advantages/Disadvantages

Indicator Dilution Dye or radioactive solution injected

into large vein

ABG

radioactive counter or photosensitve device

Indicator Dilution dye injected

avg dye conc. in blood x duration

Advantages/Disadvantages

Thermal Dilution Catheter Right Heart

Inject saline (temp. < blood) RA

Measure temp. in PA

temp / time

Thermal Dilution temp / time

Advantages/Disadvantages

CO2 Rebreathing Spirometry w/ rapid CO2 analyzer

breath by breath analysis

estimation of venous and arterial CO2 conc.

CO2 Rebreathing

CO2 production x 100

v-a CO2 difference

Advantages/Disadvantages

Cardiac Output @ Rest

Heart Rate (bpm) Stroke Volume (mL) Cardiac Output (mL)Untrained 70 71 5000Trained 50 100 5000

Immediate Response to Exercise CO 20 HR and SV

HR (later)

SV

CO linearly and directly w/ exercise intensity

Immediate Response to Exercise

Stroke Volume Starling mechanism

ventricular contractility

Cardiac Output during Maxium Exercise

Heart Rate (bpm) Stroke Volume (mL) Cardiac Output (mL)Untrained 195 113 22000Trained 195 179 35000

Training Effect on Cardiac Output SV during rest & exercise

Maximum SV: 40-50% VO2max (60-66% HR max)

SV is > from rest exercise

Factors Affecting Stroke Volume

Diastolic filling

venous return

HR

Factors Affecting Stroke Volume

Systolic Emptying

preload

enhanced by catecholamines

Training Effects

Ventricular enlarged chamber enhanced compliance enlarged myocardiumHR by 12 to 15 bpm

Final Comments on CO and SV

Stroke Volume Index

Cardiac Output Index

Blood Distribution @ Rest

Muscle20%

Heart4%

Skin6%

Brain14%Liver

27%

Kidneys22%

Other7%

(700 ml)

(700 ml)

(1000 ml)

(1100 ml)

(1350 ml)

5000 mL

(300 ml)

Blood Distribution during Exercise

84%

4%2% 4% 2%1%3% Muscle

Heart

Skin

Brain

Liver

Kidneys

Other

21,000 ml1000 ml

900 ml

500 ml

250 ml

600 ml

25000 mL

CO and Oxygen

Rest arterial blood 200 ml O2/L pump 5 L/min 1000 mL O2/min available uptake 250 ml O2/min reserve 750 ml O2/min

CO and Oxygen

Exercise arterial blood 200 ml O2/L pump 25 L/min 5000 mL O2/min available CO available O2

Meeting O2 Demands of Exercise CO

use of O2 carried by blood

O2 Uptake and Exercise

0

0.5

1

1.5

2

2.5

3

3.5

150 300 450 600 750 900 1050 1200 1350

Power Output (kgm/min)

Oxy

gen

Up

take

(L

/min

)

Arms

Legs

Athlete’s HeartMyocardial hypertrophy left ventricleResistance Training wall thickness /mass < cavity sizeEndurance volume < wall thickness

Pathological Heart 20 HTN

Myocardial hypertrophy left ventricle distended less compliant

Hypertension Systolic > 140 mmHg / Diastolic > 90

mmHg

25-33% of populations will have HTN

Prevalent in African Americans

Up to 95% of HTN is of unknown cause

Hypertension

Can result in: Heart failure MI CVA

Hypertension

Rx: Diet Exercise Weight control Stress reduction Medication

Endurance Exercise & BP

Systolic intensity 20 CO

120 200 (240 - 250)

Steady-state: may 20 arteriole dilation TPR

Endurance Exercise & BP

Diastolic little

15mmHg abnormal stop exercise/testing

Graded Exercise & BP

7090

110130150170190210

Treadmill Elevation (% Grade)

Blo

od

Pre

ss

ure

(m

m H

g)

Diastolic

Systolic

Long Term Effects of Aerobic Exercise

Training Effect: Aerobic 6 –10 mm Most effective in mild to moderate

HTN

Mechanism: sympathetic activity Altered renal function

Resistance Training & BP

Isometric (% MVC) Free Weight Bench Press

Hydraulic Bench Press

25 50 75 100 25 50 Slow

Fast

Systolic

172 179

200

225 169 232 237 245

Diastolic

106 116

135

156 104 154 101 160

Resistance Training & BP Muscle Contraction compresses

peripheral arteries ( to force)

> muscle mass > BP

480/350 mmHg 20 valsalva

Resistance Training & BPMechanism: Sympathetic

MAP (average pressure)

Cardiac output

BP = CO x TPR

Resistance Training & BP BP accommodates to regular

resistance training blunted BP response to exercise

Recovery Hypotensive response in recovery

from sustained submaximal

Upper vs. Lower Body Exercise

Systolic (mm Hg)

Diastolic (mm Hg)

% of VO2max Arms Legs Arms Legs

25 150 132 90 70

40 165 138 93 71

50 175 144 96 73

75 205 160 103 75

Upper vs. Lower Body Exercise

Upper vs. Lower Extremity Exercise and BP Response

UE: > BP response 20 smaller

musculature & vasculature > TPR

> BP response Double Product (Rate Pressure Product)

Rate Pressure Product or Double Product = SBP x HR

index of relative cardiac work

indicator of myocardial O2 uptake & coronary blood flow

Cardiovascular Regulation

Electrical Activity (intrinsic regulation)

S-A node atria A-V node A-V bundle (Purkinje fibers) ventricles

Extrinsic Regulation

Sympathetic Catecholamines HR and contractility Adrenergic fibers (norepi)

constrict Cholinergic fibers (acetylcholine)

dilatation in skeletal & cardiac muscle

Extrinsic RegulationParasympathetic Acetylcholine

HR

No effect on contractility

Vagus nerves

Extrinsic Regulation

Pre-exercise anticipation sympathetic activity

parasympathetic

Greatest HR

Extrinsic Regulation

Onset of exercise & low intensity Parasympathetic

Exercise intensity Sympathetic

Extrinsic Regulation

Central command provides greatest control of CV system

Pre-exercise anticipation 100% HR

Heart Rate Response to Exercise

Distance (yards)

start 88 176 264 352 440

60

120

180

Heart

Rate

(b

pm

)

Peripheral Input

Receptors in muscle monitor mechanical and chemical

Exercise Pressor Reflex

Peripheral Input

Receptors in arteries Baroreceptors BP sympathetic input Mechanoreceptors heart and large veins

Blood Distribution & Exercise

Blood is distributed as needed (autoregulated)

Rest - 1 of 30-40 capillaries open in muscle

tissue O2 vasodilation in skeletal & cardiac muscle