Cardiac OutputCardiac Output

““So you want to be a So you want to be a marathoner?”marathoner?”

Do you have the blood for Do you have the blood for it?it?

““Q” In The Untrained PersonQ” In The Untrained Person

In the average person, a 5-L cardiac In the average person, a 5-L cardiac output is usually sustained with a heart output is usually sustained with a heart rate of approximately 70 beats a minute.rate of approximately 70 beats a minute.

Stroke volume and cardiac output for Stroke volume and cardiac output for women usually average approximately women usually average approximately 25% below the values for men.25% below the values for men.

This “gender difference” is essentially due This “gender difference” is essentially due to the smaller body size of the average to the smaller body size of the average women.women.

Stroke volume is about 70ml at rest.Stroke volume is about 70ml at rest.

““Q” In The Endurance Q” In The Endurance AthleteAthlete

Endurance training causes the sinus node Endurance training causes the sinus node in the heart to come under greater control in the heart to come under greater control from the parasympathetic nervous system.from the parasympathetic nervous system.

At the same time there is probably a At the same time there is probably a reduction in the sympathetic activity.reduction in the sympathetic activity.

When the heart slows due to the When the heart slows due to the parasympathetic influence, this is called parasympathetic influence, this is called “vagal” tone.“vagal” tone.

Stroke volume may be 100ml at rest for Stroke volume may be 100ml at rest for the athlete.the athlete.

Heart Rate During ExerciseHeart Rate During Exercise

The large stroke volume of an endurance The large stroke volume of an endurance athlete is accompanied by a heart rate athlete is accompanied by a heart rate reduction during submaximal exercise.reduction during submaximal exercise.

Distribution of Cardiac Distribution of Cardiac OutputOutput

At rest: approximately 1/5 of blood flow is At rest: approximately 1/5 of blood flow is directed toward muscle tissue.directed toward muscle tissue.

The majority of blood is directed to the The majority of blood is directed to the digestive tract,liver,spleen,brain and digestive tract,liver,spleen,brain and kidneys.kidneys.

During exercise: the major portion of the During exercise: the major portion of the cardiac output is diverted to working cardiac output is diverted to working muscles.muscles.

Some tissues can handle a temporary Some tissues can handle a temporary reduction in blood during heavy exercise.reduction in blood during heavy exercise.

Example:blood flow to skin increases with Example:blood flow to skin increases with light/medium exercise but decreases with light/medium exercise but decreases with heavy exercise.heavy exercise.

Blood Flow to the Heart and BrainBlood Flow to the Heart and Brain

Some tissues cannot compromise their blood Some tissues cannot compromise their blood flow.flow.

The myocardium uses about 75% of the The myocardium uses about 75% of the oxygen flowing through the coronary vessels oxygen flowing through the coronary vessels at rest.at rest.

A large increase in heart rate during exercise, A large increase in heart rate during exercise, is accompanied by an increase in coronary is accompanied by an increase in coronary circulation.circulation.

This increase is up to 1 liter of blood per This increase is up to 1 liter of blood per minute.minute.

Cerebral blood flow is also increased by up Cerebral blood flow is also increased by up 30% compared to resting conditions.30% compared to resting conditions.

Extraction of Oxygen: A-V 02 Extraction of Oxygen: A-V 02 DifferenceDifference

At rest: about 75% of the blood’s At rest: about 75% of the blood’s original oxygen load is still bound to original oxygen load is still bound to hemoglobin after it makes the hemoglobin after it makes the complete tour through the body.complete tour through the body.

After training: up to 85% of the After training: up to 85% of the oxygen is removed from the oxygen is removed from the hemoglobin during exercise.hemoglobin during exercise.

But only in the But only in the specificspecific muscle fibers muscle fibers used during exercise.used during exercise.

This is due to increased capillaries, This is due to increased capillaries, mitochondria and aerobic enzymes.mitochondria and aerobic enzymes.

Cardiovascular Adjustments to Cardiovascular Adjustments to Upper Body ExerciseUpper Body Exercise

Maximal oxygen uptake during Maximal oxygen uptake during exercise with the arms is generally exercise with the arms is generally 20-30% lower than exercise with the 20-30% lower than exercise with the legs.legs.

Maximal heart rate is also much Maximal heart rate is also much lower with arm work.lower with arm work.

What is the reason ?What is the reason ? Relatively smaller muscle mass Relatively smaller muscle mass

involved.involved.

The Athlete’s HeartThe Athlete’s Heart

Cardiac hypertrophy results from Cardiac hypertrophy results from individual myofibrils thickening and individual myofibrils thickening and from an increased number of from an increased number of myofibrils.myofibrils.

This is viewed as a fundamental This is viewed as a fundamental adaptation to an increased work load.adaptation to an increased work load.

In endurance athletes the heart may In endurance athletes the heart may be up to 25% larger.be up to 25% larger.

Not sure if this is genetic endowment Not sure if this is genetic endowment or training induced or both.or training induced or both.

Shot Putter vs RunnerShot Putter vs Runner ““Isometric” athletes like wrestler, lifters Isometric” athletes like wrestler, lifters

have larger muscle mass, especially the have larger muscle mass, especially the intraventricular septum.intraventricular septum.

Lifters heart may weigh 330grams and Lifters heart may weigh 330grams and have left ventricular volume of 110ml.have left ventricular volume of 110ml.

Runners heart may weigh 308 grams and Runners heart may weigh 308 grams and have left ventricular volume of 180ml.have left ventricular volume of 180ml.

Non-athletic heart weighs 211 grams and Non-athletic heart weighs 211 grams and has left ventricular volume of 101ml.has left ventricular volume of 101ml.