Transcript Acute Cardiovascular Responses to Exercise

Assessment descriptor: Comprehensive and
detailed analysis of collected data, thorough and
insightful understanding of the mechanisms
responsible for acute effects of the cardiovascular,
respiratory and muscular systems of the body.
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Heart
Blood vessels
Blood
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The CV system regulates the delivery of 02 and
fuel to the body cells.
As we begin exercising the CV system assists
us to meet the additional demands that the
exercise is placing on the body.
They assist to deliver more 02 to the working
muscles.
They also assist to remove more CO2 and other
waste products
HR
Blood
flow
SV
AV02
diff
Q
BP
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HR is the simplest measure to gauge how hard the
CV system is working – it measures the hearts
function.
Measured in beats per minute - bpm
There is a direct link between HR and exercise
intensity.
HR can be affected by variables such as fatigue,
hydration, ambient temp, illness, and altitude.
Resting HR ranges from 60 to 82bpm! However,
endurance athletes have HR’s recorded as low as
28bpm.
Lance Armstrong’s resting HR is 32-34 with a
MaxHR of 201!!!! WOW!!!
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Just before beginning exercise you often get
an increase in HR – this is as a result as
anticipating the exercise.
This occurs because of a release of hormones
such as epinephrine (adrenaline).
HR will increase linearly with exercise
intensity, so as exercise intensity gets harder
heart rate will increase.
This continues until a person reaches their
max HR (MaxHR) and then it will plateau
(even if exercise intensity continues to
increase)
We use this MaxHR to set athlete’s training
zones.
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The general rule for working out a person’s
max HR is
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MaxHR = 220 - age
For example a 20 year old will have a MaxHR
of 220-20 = 200bpm
This is only an estimate and is based on
MaxHR slowly declining with age.
HR will vary for each individual
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HR is controlled by the parasympathetic
and sympathetic nervous system as well
as the endocrine system.
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We have no conscious control over the
parasympathetic nervous system
This system originates in the brain stem and
extends to the heart via the vagus nerve
At rest it the parasympathetic NS is dominant –
when HR is less than 100bpm
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Is the opposite side of the autonomic
sympathetic nervous system
It has the opposite effect of the
parasympathetic NS
It stimulates the heart causing an increase in
HR and an increase in the force of contractions
It is dominant when HR is over 100bpm
Conditions
SV
(mL/beat)
HR
(beats/min)
Cardiac
Output
(L/min)
Untrained
Rest
75
82
6.2
Untrained
Max exercise
112
200
22.4
Trained
Rest
105
58
6.1
Trained
Max exercise
126
192
24.2
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Stroke volume is the amount of blood ejected
from the left ventricle of the heart per beat
Stroke volume will increase with exercise to
assist meet the increased energy demands
Stroke volume is controlled during exercise by:
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Volume of venous blood return
Capacity of the ventricle to expand (distensibility)
Capacity of the ventricle to contract (contractility)
The pressure the ventricles have to contract against
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Untrained athlete
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Trained athlete
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SV at rest 60-75ml/beat
SV during max exercise – 80-115ml/beat
SV at rest 80-110ml/beat
SV during max exercise – 160-200ml/beat
Stroke volume will reach its maximum value
between 40-60% of a person’s VO2 max.
Conditions
SV
(mL/beat)
HR
(beats/min)
Cardiac
Output
(L/min)
Untrained
Rest
75
82
6.2
Untrained
Max exercise
112
200
22.4
Trained
Rest
105
58
6.1
Trained
Max exercise
126
192
24.2
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Why do you think a trained athlete has a larger
SV then an untrained athlete
Why do you think the trained athlete has a
lower resting HR?
Why do you think the trained athlete has a
lower HR whilst exercising?
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There are 3 main factors that account for
the increase in SV during exercise
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How much the ventricle fills and stretches
during diastole (relaxation period)
Increase in neural stimulation
Decrease in peripheral resistance as a result of
vasodilation of the vessels supplying blood to
the exercising muscles. This decrease means it
is easier for the heart to empty blood from the
ventricle and increases SV.
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During exercise venous blood flow increases
This causes the ventricle to stretch more as it
fills more fully with blood
This results in a more forceful contraction as a
result of the greater elastic recall
An increased amount of blood in the ventricle
results in a stronger contraction of the ventricle,
thereby increasing the amount of blood ejected
(increased SV)
Has the greatest effect at lower intensities
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At rest, the left ventricle only ejects 40-50% of
blood in it.
During exercise, the left ventricle ejects more
then that
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Cardiac output = the total volume of blood
ejected from the heart per minute
Measured in litres per min L/min
Q = SV x HR
Q(L/min) = SV(mL/beat) x HR (bpm)
Cardiac output = stroke volume x heart rate
Changes in HR and SV lead to changes in Q.
When exercising, both the SV and HR will
increase, therefore Q increases
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At the beginning of exercise and up until
approx 60% VO2 max the increase in Q comes
from the increase in HR and SV.
However, after approx 60% VO2max what
causes the increase in Q?
SV increases to its max when you are working
submaximal (upto 60%), so when you increase
intensity, the body compensates by increasing
HR, that allows Q to continue to rise
Conditions
SV
(mL/beat)
HR
(beats/min)
Cardiac
Output
(L/min)
Untrained
Rest
75
82
6.2
Untrained
Max exercise
112
200
22.4
Trained
Rest
105
58
6.1
Trained
Max exercise
126
192
24.2
Subject
SV
HR
Q
REST
Untrained male
70
60
100
80
x
x
x
x
72
75
50
55
=
=
=
=
5.0
4.5
5.0
4.4
Trained male
110
90
180
x
x
x
200
200
190
=
=
=
22.0
18.0
34.2
Trained female
125
x
190
=
23.8
Untrained female
Trained male
Trained female
MAX EXERCISE
Untrained male
Untrained female
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Systolic = the contraction or pumping phase of
the heart
Diastolic = the relaxation or filling phase of the
heart
Systolic BP = the pressure in the arteries
following contraction of ventricles as blood is
pumped out of the heart
Diastolic BP = pressure in the arteries when the
heart relaxes and the ventricles fill with blood
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BP increases with exercise
During exercise when we are using large
muscles groups such as running, swimming
and cycling affects the systolic BP more than
the diastolic BP
During max exercise systolic BP can increase
from 120mmHg to 200mmHg
Upper body exercises often see a greater
increases in BP than lower body exercises
Doing resistance activities can cause even
greater increases to systolic BP
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During exercise, arterioles vasodilate (increase
in diameter), which means more blood drains
from the arterioles into the muscles capillaries.
It also means the blood needs to be ejected out
of the heart better to cater for this, therefore
increase in blood pressure
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The blood returning to the heart
When exercising, Q increases, which means
more blood is taken away from the heart,
therefore more blood needs to be returned to
the heart
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This occurs in three ways:
The muscle pump – muscles constantly contracting
squashed veins together, which makes blood travel back
to the heart in the ‘smaller’ vein at a more forceful pace
 The respiratory pump – (similar as above) Breathe in
increase abdominal pressure, which pushes blood in
veins in thorax and abdomen towards the heart.
Breathing out allows pressure to drop and veins to refill.
When RR increase due to exercise, this pump increases
 Vasoconstriction – forces the veins to constrict, which
forces blood to be pushed back to heart quicker
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Blood volume decreases during exercise,
especially in the first 5minutes (it then
stabilises)
The amount of decrease in blood volume is
dependant on the intensity of the exercise,
environmental factors such as temperature and
level of hydration
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During exercise blood flow redistributes – know as
redistributed blood flow
A person of average fitness, during max exertion
has blood flow greater than water from a kitchen
tap!
As soon as exercise begins blood flow is
redistributed – WHY?
To increase the blood flow to the working muscles
and a reduction the blood flow to organs
This occurs to meet the bodies needs for increased
O2 and nutrients and removal of CO2
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Redistributed blood flow occurs as a result of
vasoconstriction and vasodilation
Vasodilation = widening of the blood vessels
causing an increase in blood flow
Vasoconstriction = narrowing of the blood vessels
causing a decrease in blood flow
The blood vessels in regions requiring increases in
02 and nutrient delivery vasodilate
The blood vessels in regions requiring decreases in
02 and nutrient delivery vasoconstrict
These adjustments occur according to intensity
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Vasodilation occurs with blood vessels near
the:
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Working muscles
Vasoconstriction occurs with blood vessels
near the:
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Spleen
Kidney
Gastrointestinal tract
Inactive muscles
Heart gets greater
supply of blood
during exercise, not
just more pumped
there but the heart
muscle itself gets
more blood because
of vasodilation of
the coronary
arteries
Blood directed at
the brain doesn’t
decrease by as
much
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This also allows for increases in the surface
area of capillaries
This increases the area over which gaseous
exchange occurs
This occurs because we need to increase blood
supply up to 20 times greater than rest and this
can not be achieved by Q alone
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Blood flow to the skin increase as it needs to
assist in the regulations of body temperature
through heat exchange with the environment
As exercise intensity increases, blood flow to
the skin also increases
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VO2 is the volume of O2 that can be taken up
and used by the body
As intensity increases, so does O2 consumption
(we know this occurs because ventilation and
cardiac output increase.
A-VO2 difference also increase
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A-VO2 diff is the measure of the difference in
the concentration of O2 in the arterial blood
and the concentration of oxygen in the venous
blood
Measured in millilitres per 100millilitres of
blood
At rest our a-VO2 diff is approx 5mL per
100mL – arteries contain approx 20mL/100mL
and the veins carry approx 15mL/100mL
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About 25% of 02 is extracted from the arterial
blood by the working muscles at rest. The other
75% goes back to the heart in venous blood
During exercise that increases to approx 75% of
available 02 is extracted – up to 1518mL/100mL