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Exercise and the Heart
O2 Delivery
 Q increase is in direct
proportion to the O2
demand of the
 Heart Rate
 Stroke Volume
 Blood pressure
 Systolic
 Diastolic
 a-v O2 Difference
Redistribution of Blood Flow
 Muscle blood flow to working
skeletal muscle
 Splanchnic blood flow  to less
active organs (Liver, kidneys, GI
tract, etc.)
Redistribution of Blood Flow
During Exercise
Fig 9.19
(c) 2004 The McGraw-Hill Companies, Inc. All rights reserved.
Redistribution of Blood Flow
Increased Blood Flow to Skeletal
Muscle During Exercise
 How?
 Withdrawal of sympathetic
 Autoregulation
 Blood flow increased to meet metabolic
demands of tissue
 Vasodilation:  O2 tension,  CO2
tension, pH, potassium, adenosine,
nitric oxide
Circulatory Responses to
 Depend on:
 Type, intensity, and duration of
 Environmental condition
 Emotional influence
Transition From Rest  Exercise
and Exercise  Recovery
 Rapid increase in HR, SV, cardiac
 Plateau in submaximal (below
lactate threshold) exercise
 O2 supply = O2 demand
 Recovery depends on:
 Duration and intensity of exercise
 Training state of subject
O2 supply = O2 demand
O2 supply < O2 demand
From Rest
 Exercise
 Recovery
 O2 supply > O2 demand
 What is the extra oxygen used for?
 Restore O2 inside muscles (myoglobin)
 Removal of lactic acid
 Reduce body temperature
Incremental Exercise
Heart rate and cardiac output
 Increases linearly with increasing work
 Reaches plateau at 100% VO2max
Systolic blood pressure
 Increases with increasing work rate
Incremental Exercise
 Stroke Volume
 Reaches
plateau at 4060% VO2max
 Why?
Arm vs. Leg Exercise
 At the same oxygen uptake arm work
results in higher:
 Heart rate
 Due to higher sympathetic stimulation
 Blood pressure
 Due to vasoconstriction of large inactive
muscle mass
Heart Rate
and Blood
During Arm
and Leg
Prolonged Exercise
 Cardiac output is maintained
 Gradual decrease in stroke volume
 Gradual increase in heart rate
 Cardiovascular drift
 Due to dehydration and increased
skin blood flow (rising body
Fig 9.22
HR, SV, and CO During
Prolonged Exercise
Fig 9.22
Cardiovascular Adjustments
to Exercise
Fig 9.23
Summary of Cardiovascular
Control During Exercise
Initial signal to “drive”
cardiovascular system comes
from higher brain centers
Fine-tuned by feedback from:
Fig 9.24
A Summary
Fig 9.24