AS PE
CARDIOVASCULAR SYSTEM
HEART RATE
STROKE VOLUME
CARDIAC OUTPUT
LEARNING OBJECTIVES
1.
Can I explain what happens to the CV
system at rest?
2.
Can I explain what happens to the CV
system during exercise?
BLP LEARNING HABITS

Listening and Questioning
STARTER – EXAM QUESTIONS
d) Describe how the conduction system of the heart
controls the cardiac cycle.
(3 marks)
c) Endurance (aerobic) performance is dependent
upon the heart supplying blood to the muscles.
Describe the flow of blood through the heart
during the cardiac cycle (Diastole and Systole
Phases).
(4 marks)
RESTING VOLUMES AND
DEFINITIONS – HEART RATE



This is the number of times the Heart ventricles
beats in One minute. The average resting HR is 72
beats per minute (bpm). The maximum HR is
calculated by subtracting your age from 220.
Low resting HR may indicate a high level of
aerobic/endurance fitness. Highly trained athletes
can have a resting HR as low as 28 bpm
A resting HR below 60 bpm is termed bradycardia
(or slow HR), due to increase in Stroke Volume due
to an increase size of the heart muscle (called
hypertrophy)
RESTING VOLUMES AND
DEFINITIONS – STROKE VOLUME



This is the volume of blood ejected from the
ventricles every beat
This is the difference in volume of blood in the
ventricles before and after the ventricles contract
The following terms are used to measure SV:
–
–
–
End-diastolic volume (EDV) – volume of blood in
ventricles at the end of relaxation phase (before
contraction)
End-systolic volume (ESV) – volume of blood in ventricles
at the end of contraction phase (after contraction)
Resting EDV is about 130ml; resting ESV is about 60ml.
Therefore, resting SV is about 70ml
RESTING VOLUMES AND
DEFINITIONS – CARDIAC OUTPUT




This is the volume of blood ejected by the
heart ventricles in one minute (can also be
called Q)
The resting value is about 5 litres per minute
Q
=
(L/min)
SV
(ml per
beat)
x
HR
(beats per min)
RESPONSE TO EXERCISE – STROKE
VOLUME



As an athlete starts running, their SV increases
linearly as their running speed/intensity increases
(only up to 40-60% of max running speed). SV will
then reach a plateau
SV is determined by the heart’s ability to fill and
empty each beat.
Ability of heart to fill is dependent on:
–
–

Venous return – SV increases due to an increase in blood
returning to the heart
The ventricles are able to stretch further
Ability of heart to empty is dependent on:
–
–
Greater EDV provides a greater stretch on the heart walls
A greater stretch increases the force of ventricular systole
(contraction of ventricles)
RESPONSE TO EXERCISE – STROKE
VOLUME


These increase ventricular contractility
(capacity of the ventricles to contract) which
almost completely empties the blood from
the ventricles
During exercise EDV = 130ml; ESV = 10ml;
therefore SV = 120ml
RESPONSE TO EXERCISE – HEART
RATE



HR will change before, during and after exercise
depending on the exercise being taken
HR will increase above resting values before
exercise takes place. This is called the anticipatory
rise which is the early release of adrenaline which
stimulates the SA node to increase HR
HR increases as exercise intensity increases but
slows down just before maximal HR values
RESPONSE TO EXERCISE – HEART
RATE




HR decreases as exercise intensity decreases
HR reaches a plateau during sub-maximal work,
which represents the optimal steady state HR for
meeting the demand for oxygen at that specific
intensity of work
HR decreases rapidly after exercise stops due to a
decrease in demand for oxygen by the working
muscles
A more gradual decrease in HR towards resting
levels, but still elevated to allow the body to recover
– this is oxygen debt (additional oxygen
consumption during recovery, above that usually
required when at rest)
RESPONSE TO EXERCISE – CARDIAC
OUTPUT



Increases directly in line with exercise
intensity from resting values of 5 L/min to
maximal values of 20-40 L/min in highly
trained endurance athletes
Q primarily increases to supply the increase
in demand for oxygen from our working
muscles
When exercise intensity exceeds 40-60% of
an athlete’s maximal exercise intensity, SV
begins to plateau. Any further increase in Q
is a result of an increase in HR
RESPONSE TO EXERCISE – CARDIAC
OUTPUT

Here is a summary of HR, SV and Q values related to
exercise intensity:
EXERCISE INTENSITY
Value
Resting
Sub-Max
Max
HR
70-72
Up to 100 130
220 minus
your age
SV
Q
60 - 80ml 80 - 100ml
80 - 110ml untrained
160 - 200ml
trained
5 L/min
Up to 10
L/min
100 - 120
untrained
160 - 200
trained
20 - 40
L/min
PLENARY
1.
How do you think HR, SV and Q will change
with exercise?