Cardiovascular System and Exercise

CV System’s Important Functions During Physical Activity

n   Deliver O2 to active tissues, e.g. muscle

n   Aerates (put O2 into) blood returned to lungs

n   Transport heat from body’s core to skin

n   Deliver fuel nutrients to active tissues

n   Transport hormones to target organs

Components of CV System

n    Heart

   4 chambers/2 pumps

§   Right atrium and ventricle (provide blood to lungs in order to pick up O2 – “pulmonary circulation” pump)

§   Left atrium and ventricle (provide blood to body – “systemic circulation” pump)


n    Vascular system

§   Arteries – takes O2 to body tissues

§   Capillaries – transfer gases, nutrients, and waste products across tissues

§   Veins – return unoxgenated blood to heart via one-way action of its valves

The Venous System

n    Contains ~ 65% of total blood volume

   This serves as a reserve for maintaining appropriate amount of blood in vascular system

n    Potential problem

   Varicose veins – distension of superficial veins due to poor circulation

§   In severe cases, these veins become inflamed and degenerate (phlebitis)

§   May be prevented by regular rhythmic -physical activity

n    Active cool-down

   Important, not only for lactate removal but also prevention of blood pooling


Blood Pressure

n    Amount of pressure exerted on the vascular system

n    Measured by:

    Systole – pressure exerted on blood vessels upon contraction of the heart

    Diastole – pressure exerted on blood vessels when heart is relaxed

n    Typical numbers

    120/80 is an average “good” blood pressure


§    Systolic BP of 140-159 or Diastolic of 90-99    (Stage 1)

§                        160-179                     100-109 (Stage 2)

§                         > 180                         > 110  (Stage 3)

Blood Pressure Response to Exercise

Comparison of Aerobic vs Resistance Training BP’s

Comparison of Upper vs Lower Body Exercise with BP

Body Inversion and
Blood Pressure

n    Devices that allow an individual to hang upside-down have been used for:

§   Relaxation

§   Facilitate strength-training response

§   Relieve low back pain

 * None of these have been proven by research


n    These devices put extreme pressure within the eye; should be avoided also in individuals with hypertension

Recovery Blood Pressure

n   Will decrease upon cessation of exercise

   Systolic pressure may actually decrease below resting values up to 12 hours post-exercise

§   Occurs primarily after light-to-moderate intensity exercise

§   Due to pooling of blood in lower extremities

§   May be beneficial for hypertensive therapy

Heart Function

Heart’s Blood Supply

n    Coronary circulation

Myocardial O2 Utilization

n   Heart extracts 70-80% of its O2 need from coronary vessels at rest

§   Other tissues can only extract about 25% from available capillaries

n      Mechanical factors that affect heart’s uptake of O2

   Tension development within myocardium

   Contractility of heart

   Heart rate


Myocardial Work

n    How do we measure the heart’s effort?

   Rate Pressure Product (RPP) = SBP x HR

           or Double Product


§      RPP helps predict possibility of heart problems

§      Typical RPP values:

§    6000 at rest  (HR = 50 bpm; SBP = 120 mmHg)

§    40,000 during intense exercise  (HR = 200 bpm; SBP = 200 mmHg)


Heart’s Energy Supply

n   Relies almost exclusively on aerobic metabolism

   Myocardial fibers have greatest mitochondrial content of any body tissues

   Rely on energy from glucose, fatty acids, and lactate

§   May get as much as 50% of its total energy from circulating lactate

§   During prolonged submaximal exercise, may derive up to 70% of its energy from fat metabolism

Heart Regulation

n    Intrinsic control

   Specialized cells (sino-atrial node) send out and carry electric signal through the heart on a rhythmic basis

§   i.e. resting HR  (60-100 bpm)


n    Extrinsic control

   Nervous System

§   Sympathetic – speeds up heart and increases contractility

§   Parasympathetic – slows down heart rate

   Hormonal System

§   Regulates heart function in response to exercise


Electrical System of Heart

Normal vs Abnormal HR

n   60-100 bpm – normal range for resting HR


n   < 60 bpm – bradycardia


n   > 100 bpm - tachycardia

How do we follow the Heart’s Electrical Activity?

The ECG Tracing

Peripheral Inputs to alter HR and BP with Exercise

n    Mechanoreceptors

     sensors in skeletal muscles that signal the cardiovascular control center in the medulla to activate changes in blood flow and heart rate

n    Chemoreceptors

     sensors in blood vessels joints, and muscles detect changes in chemical status of body and subsequently signal cardiovascular control center to elicit appropriate responses

n    Baroreceptors

     sensors in aortic arch and carotid sinus respond to changes in pressure.  As pressure increases, vessels stretch causing HR to slow and peripheral blood vessels to dilate.  These receptors are believed to  prevent abnormally high BP with exercise

     carotid artery palpation can possibly decrease HR response


n   Irregularities in heart rhythm

   Can occur in the Atria

   Can occur in the Junctional Tissue (between atria and ventricles)

   Can occur in the Ventricles

Atria ECG Irregularities

Atrial ECG Irregularities

Atrial ECG Irregularities

Junctional ECG Irregularities

Ventricular ECG Irregularities

Ventricular ECG Irregularities

Ventricular ECG Irregularities

Ventricular ECG Irregularities

n   Ventricular Tachycardia – 3 or more PVC’s in a row


n   Ventricular Fibrillation – 3 or more PVC’s with no regularity

   This is a emergency situation; may lead to stopping of heart

Blood Distribution

n   Exercise Effect

   Blood vessels near active muscles will dilate while vessels close to inactive tissues will tend to constrict

How is blood flow regulated?

n   Based upon the following equation:

        Flow = Pressure ÷ Resistance


n    3 factors determine resistance to blood flow:

   Viscosity (or blood thickness)

   Length of conducting tube

   Radius of blood vessel  (primary factor affecting flow)



Muscle regulation of blood flow

n   At rest, one out of 30-40 capillaries remains open in muscle

n   Remainder of capillaries are available for blood flow during exercise.  These dormant capillaries serve 3 functions:

   Increase blood flow when needed

   Increase blood volume when needed

   Increase effective surface area for gas (O2 and CO2) and nutrient exchange in muscle

Cardiovascular Dynamics
During Exercise

n   Cardiac Output – indicator of how well the cardiovascular system is working


        Cardiac Output = HR x Stroke Volume


        Cardiac Output = VO2 (ml/min)  X  100

                                        aVO2 diff


a-VO2 Difference

n    The difference in the amount of oxygen in the artery vs the vein after blood flows through the muscle.

n      Example:  20 ml O2 – 15 ml O2 = 5 ml O2

Resting Cardiac Output

n   Approximately 5 liters/min

   Both in untrained and trained individuals

§   Example “Untrained”

   C.O. = HR x SV

              = 70 bpm x 71 ml per beat

                 = 5 liters/min

§   Example “Trained”

   C.O. = HR x SV
     = 50 bpm x 100 ml per beat
     = 5 liters/min

What accounts for Athletic Heart?

n   Increased vagal tone ( parasympathetic activity) slows heart rate and allows for more filling time


n   Enlarged ventricular volume due to bigger heart and improved ability to stretch


n   More powerful contraction due to bigger heart

Exercise Cardiac Output

n    Blood flow from heart increases in direct proportion to exercise intensity

Cardiac Output Response to Exercise

Heart Rate Response to Exercise

Stroke Volume Response to Exercise

Why doesn’t stroke volume increase linearly?

n   Limitation of available space to fill with blood in the left ventricle


n   Ability to contract

Cardiac Output Distribution

n     At rest:

§    27% of blood goes to liver

§    22% of blood goes to kidney

§    20% of blood goes to muscles

§     4% of blood goes to heart

§    14% of blood goes to brain

§     6% of blood goes to skin

§     7% of blood goes to remainder of body tissues


n     During Intense Exercise

§    2% of blood goes to liver

§    1% of blood goes to kidney

§    84% of blood goes to muscles

§     4% of blood goes to heart

§     4% of blood goes to brain

§     2% of blood goes to skin

§     3% of blood goes to remainder of body tissues