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

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

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 myocardium HR  by 12 to 15 bpm

Final Comments on CO and SV Stroke Volume Index Cardiac Output Index

Blood Distribution @ Rest 5000 mL (1000 ml) (700 ml) (1100 ml) (300 ml) (700 ml) (1350 ml)

Blood Distribution during Exercise 25000 mL 1000 ml 21,000 ml 600 ml 900 ml 500 ml 250 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

Athlete’s Heart Myocardial hypertrophy left ventricle Resistance Training  wall thickness /mass <  cavity size Endurance  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

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 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 & BP Mechanism:  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 25 150 132 90 70 40 165 138 93 71 50 175 144 96 73 75 205 160 103

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 Regulation Parasympathetic 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 180 Heart Rate (bpm) 120 60 start 88 176 264 352 440 Distance (yards)

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