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