Cardiovascular Adaptations

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Cardiovascular Adaptations to Exercise
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Cardiac Output (Q)
Cardiac output Q has been defined as the amount
of blood pumped from the heart per minute .
Q (mL/min) HR (beats/min) x SV (mL/beat)
Therefore, cardiac output can be altered by
changing heart rate and/or stroke volume.
When thinking about cardiac output, remember that
the object of the heart is to get oxygenated
blood to the body. Therefore any activity that
requires an increase of oxygen to the
muscles/body will be accompanied by an increase
in cardiac output (and vice versa).
QMAX decreases with age (HRMAX ? ? Age?)
Q can increase up to 5 times with intense
activity!
Cardiovascular Adaptations to Exercise
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Cardiac Output (Q)
While heart rate is controlled by the SA node, it
is regulated by

• Parasympathetic nervous system (slows down)

2. Sympathetic nervous system (speeds up)
3. Body temperature (?T ? ?HR)
Stroke volume is regulated by three factors

• Pre-load (Left Ventricle End Diastolic Volume
  LVEDV)

2. Afterload (pressure in the aorta heart is
pushing against)
3. Strength of ventricular contraction
Cardiovascular Adaptations to Exercise
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Stroke Volume (SV)

• Pre-load (LVEDV)

LVEDV the amount of blood remaining in the
left ventricle after diastole.
Frank Starling Law the myocardium of the
left ventricle is elastic and has the ability to
stretch. The more blood in the ventricle (EDV),
the more it stretches. Fibres lengthen,
resulting in more forceful contraction and
therefore increased stroke volume.
Ejection fraction (EF) - percentage of
proportion of blood ejected from left ventricle
each heartbeat.
Cardiovascular Adaptations to Exercise
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Stroke Volume (SV)
2. Afterload (pressure in the aorta heart is
pushing against)
The pressure in the left ventricle must
exceed the pressure in the aorta in order to
pump blood to the body.
During exercise, aortic pressure drops due
to arteriole dilation.
3. Strength of ventricular contraction
Circulating hormone (epinephrine/norepinephri
ne) in the blood during exercise increases the
amount of calcium available to the heart
resulting in greater contractile ability.
Cardiovascular Adaptations to Exercise
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Oxygen Delivery to Muscles During Exercise
1. Changes in cardiac output (Q)
2. Redistribution of blood flow
Cardiovascular Adaptations to Exercise
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Oxygen Delivery to Muscles During Exercise
1. Changes in cardiac output (Q)

• cardiac output increases depending on the
  intensity of the activity (greater demand for
  oxygenated blood)

• Initially there is an increase in both HR and SV,
  bringing Q to a constant (higher) level

• untrained to moderately trained individuals will
  experience leveling off of SV 40 of VO2 max
  (this does not happen in endurance athletes
  (better ventricle refilling capacity)

Cardiovascular Adaptations to Exercise
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Cardiac output Incremental Exercise

• HR and Q increase in proportion to VO2 (greater
  demand for O2 satisfied)
• HR and Q plateau at VO2 max
• Increase in Q is able to take place due to
  increased sytolic pressure and decreased
  peripheral resistance

Cardiovascular Adaptations to Exercise
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Oxygen Delivery to Muscles During Exercise
During prolonged exercise, SV decreases slightly
due to fluid-loss. The HR increases to maintain
a constant Q.
This phenomena is known as cardiovascular drift.
It is brought on by increased body temperature
which results in

• decrease in blood plasma volume

• redistribution of blood flow to the skin

• dehydration

The net result being a decrease in venous return
to the heart and therefore decreased SV.
Cardiovascular Adaptations to Exercise
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Cardiac output Prolonged Exercise
"Cardiovascular Drift"
Cardiovascular Adaptations to Exercise
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Cardiac output Rest Exercise Recovery

• Rapid increase in SV, HR (Q) at the onset of
  exercise
• If below the lactate threshold, steady state is
  reached in 1- 4 minutes (like VO2)
• Recovery from low intensity exercise is
  relatively quick
• Trained athletes recover quicker as HR doesnt
  reach same level

Cardiovascular Adaptations to Exercise
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Oxygen Delivery to Muscles During Exercise
Cardiovascular Adaptations to Exercise
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Oxygen Delivery to Muscles During Exercise
2. Redistribution of blood flow
In order to meet demand of skeletal muscles for
oxygen, during exercise

• Blood flow to the muscles increases
  (15 20 of
  Q at rest ? 80 85 of Q during maximal
  exercise)

• Blood flow to liver, kidneys, GI tract and skin
  is reduced

• Blood flow to the brain and heart are increased
  (absolute values, not
  of total)

Cardiovascular Adaptations to Exercise
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Oxygen Delivery to Muscles During Exercise
Distribution of blood flow at rest and during
exercise shown as cardiac output.
Cardiovascular Adaptations to Exercise
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Blood Pressure Responses to Exercise
Blood pressure varies widely during exercise
depending on type, duration and intensity of the
activity.

• Type Aerobic Systole (prolonged ? increase,
  then decrease
• 
  because of
  arteriole dilation)
• Diastole
  (unchanged)
  
• Anaerobic Systole Diastole (short, large
  increases)

2. Intensity Greater intensity greater rise in
systolic pressure
Cardiovascular Adaptations to Exercise
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Effects of Training on the Cardiovascular System

• Improvements in efficiency at rest and sub-max
  and maximal exercise

• ? mass and dimensions of the heart (change In
  myocardium)

• ? ventricular volume

• ? thickness of ventricular walls

• ? stroke volume

• ? force of contraction of ventricle

• ? Q

• ? of capillaries that deliver blood to the
  myocardium

• ? diameter of coronary arteries

• ? blood volume (plasma, erythrocytes)

• ? HR

• Bradychardia (HR ? 60 bpm)

Cardiovascular Adaptations to Exercise