Transcript cardiac output

Cardiac Output
“So you want to be a
marathoner?”
Do you have the blood for it?
“Q” In The Untrained Person
In the average person, a 5-L cardiac output is
usually sustained with a heart rate of
approximately 70 beats a minute.
 Stroke volume and cardiac output for women
usually average approximately 25% below the
values for men.
 This “gender difference” is essentially due to the
smaller body size of the average women.
 Stroke volume is about 70ml at rest.
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“Q” In The Endurance Athlete
Endurance training causes the sinus node in the
heart to come under greater control from the
parasympathetic nervous system.
 At the same time there is probably a reduction in
the sympathetic activity.
 When the heart slows due to the
parasympathetic influence, this is called “vagal”
tone.
 Stroke volume may be 100ml at rest for the
athlete.
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Heart Rate During Exercise
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The large stroke volume of an endurance athlete
is accompanied by a heart rate reduction during
submaximal exercise.
Distribution of Cardiac Output
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At rest: approximately 1/5 of blood flow is
directed toward muscle tissue.
The majority of blood is directed to the
digestive tract,liver,spleen,brain and kidneys.
During exercise: the major portion of the
cardiac output is diverted to working muscles.
Some tissues can handle a temporary
reduction in blood during heavy exercise.
Example:blood flow to skin increases with
light/medium exercise but decreases with
heavy exercise.
Blood Flow to the Heart and Brain
Some tissues cannot compromise their blood
flow.
 The myocardium uses about 75% of the oxygen
flowing through the coronary vessels at rest.
 A large increase in heart rate during exercise, is
accompanied by an increase in coronary
circulation.
 This increase is up to 1 liter of blood per minute.
 Cerebral blood flow is also increased by up 30%
compared to resting conditions.
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Extraction of Oxygen: A-V 02 Difference
 At
rest: about 75% of the blood’s original
oxygen load is still bound to hemoglobin
after it makes the complete tour through
the body.
 After training: up to 85% of the oxygen is
removed from the hemoglobin during
exercise.
 But only in the specific muscle fibers used
during exercise.
 This is due to increased capillaries,
mitochondria and aerobic enzymes.
Cardiovascular Adjustments to
Upper Body Exercise
 Maximal
oxygen uptake during exercise
with the arms is generally 20-30% lower
than exercise with the legs.
 Maximal heart rate is also much lower
with arm work.
 What is the reason ?
 Relatively smaller muscle mass involved.
The Athlete’s Heart
 Cardiac
hypertrophy results from
individual myofibrils thickening and from
an increased number of myofibrils.
 This is viewed as a fundamental
adaptation to an increased work load.
 In endurance athletes the heart may be
up to 25% larger.
 Not sure if this is genetic endowment or
training induced or both.
Shot Putter vs Runner
 “Isometric”
athletes like wrestler, lifters
have larger muscle mass, especially the
intraventricular septum.
 Lifters heart may weigh 330grams and
have left ventricular volume of 110ml.
 Runners heart may weigh 308 grams and
have left ventricular volume of 180ml.
 Non-athletic heart weighs 211 grams and
has left ventricular volume of 101ml.