The Effect of Exercise
on the
Cardiovascular System
Effect during rhythmic exercise (jogging)
1.
2.
3.
4.
5.
Blood vessels dilate in active muscles
Muscles pump (push) the blood to
circulate faster
Increased blood flow increases the
systolic blood pressure initially, then the
systolic pressure will level off (approx
140-160)
The diastolic pressure does not increase
significantly
This response is similar for conditioned
and unconditioned individuals
Response to sub-maximal exercise
unconditioned
140 mmHg
conditioned
120 mmHg
Jogging
time
Initial minutes
2-3 hours after exercise
recovery
Effect during resistance exercise (lifting)
1. More dramatic changes are
seen
2. Strained muscle activity
compresses peripheral
arteries causing significant
resistance to blood flow and
an increase in blood pressure
3. This is dangerous to
individuals with HTN (high
blood pressure) or heart
disease
Response to resistive exercise
190 mmHg
170 mmHg
unconditioned
140 mmHg
conditioned
120 mmHg
Blood pressure changes are more dramatic with
resistance exercise to the upper extremities
(compared to the lower extremities)
• Upper extremity muscles cause greater
resistance to blood flow in the smaller arterioles
in the upper extremities
• Lower extremity muscles cause less resistance
to blood flow in the larger arterioles of the lower
extremities
Recovery
1. After sustained sub-maximal exercise, systolic
blood pressure is reduced below pre-exercise
levels for 2 – 3 hours in all subjects (normal or
individuals with high blood pressure)
2. Blood pressure (diastolic and systolic) appear
to be lower with a regular exercise program
BEFORE TRAINING
at rest
139/78
during exercise
173/92
AFTER 4 -6 WEEKS
of SUB- MAXIMAL
EXERCISE
TRAINING
133/73
155/79
Why does regular exercise decrease
blood pressure?
Not fully understood
May be an effect on the sympathetic
nervous system
May be the increased elimination of
Na (sodium) which decreases blood
volume which decreases blood
pressure
Resistance training causes a short
term increase in blood pressure
during the exercise, but no long term
rise in blood pressure noted
Oxygen supply to the heart
1. Normal tissues use 25% of oxygen in the blood
2. Heart muscle uses 70-80% of oxygen in the
blood
3. Exercise can increase coronary blood flow 4-6
times
4. Exercise increases myocardial metabolism
– If blood flow is restricted (due to coronary
disease) chest pain results
– Stress tests are done during exercise to
measure the demand on the heart
Energy for the heart
 Myocardium (heart muscle) has the greatest
number of mitochondria per cell (compared to all
muscles in the body)
 Myocardium uses glucose, fatty acids, and lactic
acid (from skeletal muscle activity) for energy
 During sub-maximal exercise, the heart muscle
may get up to 50% of its energy from lactic acid
Cardiovascular regulation and
integration
• Nerves and chemicals regulate
vasodilation (opening of blood vessels)
• Nerves and chemicals regulate heart rate
• The heart, at rest, regulates itself at rate of
60-80 b/m (beats per minute)
• Nerves and chemicals can reduce that rate
as low as 30 b/m in a conditioned athlete
• Nerves and chemicals can increase that
rate as high as 220 b/m during maximum
exercise
Athletes have a high heart rate before events
called an anticipatory response
• Sprinters increase the most – up to 148 b/m (74%
of the entire increase in the event)
• Heart rate increase is progressively less with
longer distance events (long distance runners have
a higher anticipatory heart rate than the highest
heart rate of the whole event)
Distribution of blood
(arterial)
 Vasodilatation in active muscles will increase
blood flow significantly
• At rest, only 1 of 30-40 capillaries in muscle tissue are
open
• Exercise will open these capillaries
– This increases the exchange surface area between
blood and muscle cells
– This is stimulated mostly by sensors in the tissue that
sense an increased demand for oxygen
– Increased circulation is also stimulated by tissue’s
increased temperature, and increased carbon dioxide
levels
Distribution of blood
(venous)
 Adequate venous return is also important for regulating
distribution of blood
– This is achieved by action of muscles (pushing blood
along)
 Also achieved by venous valves (prevention of back
flow)
Distribution of blood
At rest
Muscles = 20%
During Exercise
increases significantly in
active muscles
Brain = 14%
increases
Skin = 6%
increases especially in hot
weather in order to lose heat
Heart = 4%
increases blood flow
proportionately with increased
cardiac output
Kidneys = 22%
decreases to about 1%
• Kidney, at rest, receives 1100 ml/min of
blood (20% of cardiac output)
• Kidney, during heavy exercise, receives
only 250 ml/min (less than 1%)
Cardiac output (CO)
• Measures the functional capacity of the
circulation to meet the demands of physical
activity
• CO is equal to HR (heart rate or rate of
pumping) times SV (stroke volume or quantity of
blood ejected in each ventricular contraction)
CO = HR X SV
Let’s try these problems!
At rest (untrained individual)
• Entire blood volume (5000 ml) is pumped out of
the left ventricle each minute - this is the same
for trained and untrained individuals (males)
CO = 5000ml/min
• Untrained person at rest average
HR is 70 b/m
• Now substitute the values in the equation below
to solve for the stroke volume (SV)
CO = HR x SV
CO = HR x SV
5000 ml/min = 70 b/m x SV
SV = 71 ml/beat
(the average stroke volume
for an untrained individual)
At rest (trained individual)
• Remember, CO stays constant
CO = 5000ml/min
• Endurance athletes at rest average
HR = 50 b/m
• Now substitute the values in the equation below
to solve for the stroke volume (SV)
CO = HR x SV
CO = HR x SV
5000 ml/min = 50 b/min x SV
SV = 100 ml/beat
(the average stroke volume
for a trained individual)
AT REST
CARDIAC
OUTPUT
HEART
RATE
STROKE
VOLUME
UNTRAINED
5000 ml/min
70 b/min
71 ml/b
TRAINED
5000 ml/min
50 b/min
100 ml/b
In conclusion:
• CO (cardiac output) stays the same at rest
for trained and untrained individuals
• The heart rate (HR) decreases with
training.
WHY?
Why?
Endurance training strengthens heart
muscle and allows the heart to pump with
more force pushing out more blood per
stroke (ventricular contraction)
Because the stroke volume is greater in
conditioned persons, the heart rate can be
lower, the heart does not have to beat as
many times/minute to maintain the
necessary cardiac output.
Is this same effect seen during
exercise?
Blood flow increases rapidly at first,
then rises gradually until it reaches a
plateau
During exercise in an untrained
person
CO increases to ~22,000 ml/min
HR increases to ~195 b/min
What is the stroke volume?
CO = HR x SV
22,000 ml/min = 195 b/min x SV
SV = 113 ml/beat
An Olympic athlete exercising
(at the same level as the previous individual)
CO increases to 22,000 ml/min
HR will increase to ~150 b/min
What is the stroke volume?
CO = HR x SV
22,000 ml/min = 150 b/min x SV
SV = 147 ml/beat
DURING EXERCISE
CARDIAC
OUTPUT
UNTRAINED 22,000 ml/min
TRAINED
22,000 ml/min
HEART
RATE
STROKE
VOLUME
195 b/min
113 ml/b
150 b/min
147 ml/b
What happens when both
individuals perform maximum
exercise?
** We will have both individuals work up to a
pulse of 195 b/min **
MAXIMUM EXERCISE
CARDIAC
OUTPUT
UNTRAINED 22,000 ml/min
TRAINED
35,000 ml/min
HEART
RATE
STROKE
VOLUME
195 b/min
113 ml/b
195 b/min
179 ml/b
In conclusion:
The untrained person increases his cardiac
output mainly due to an increased pulse
*The trained athlete increases his cardiac
output mainly due to an increased stroke
volume
*Stroke volumes are larger in athletes at rest
and during exercise, therefore the HR (pulse)
does not need to rise as much in either case
Oxygen transport in the blood remains
constant
• The blood carries about 200 ml of oxygen
per liter of blood
• The hemoglobin is about 100% saturated
and can not increase what it carries
• The body tissues use about 25% of
circulating oxygen from the blood at rest
• Increased demands of the tissues during
exercise is met by increased cardiac out
put, not more oxygen in the blood
Oxygen up-take increases with exercise
At rest - tissues use 25% of oxygen in the
blood (~50 ml per liter of blood)
During exercise – tissues may use up to
75% of oxygen in the blood(~150 ml/l of
blood)
After 55 days of training – tissues may
use up to 85% of oxygen in the blood
(~175 ml/l of blood)
How does oxygen uptake increase with
exercise?
• This increased oxygen up-take is due
primarily to increased blood flow in the
tissues
• also training increases the muscle cell’s
ability to metabolize oxygen (with greater
numbers of mitochondria)
Patients with heart disease can improve
oxygen use (by improving the tissue’s
oxygen up-take) even if heart rate and
stroke volume are unable to improve