THE PHYSIOLOGY OF FITNESS
The body’s response to acute exercise
Part Two: Respiratory Response
Session Outcomes



List two responses of the respiratory system to acute
exercise
Describe the processes involved in one response of
the respiratory system
Explain why the process occurs and the benefits it
generates for exercise
Recap :
Responses to physical activity



Can be acute or
chronic
Acute – body’s
immediate responses
to exercise
Chronic – adaptations
to the body that occur
through regular
training
Responses to physical activity
Respiratory
responses:
1.
Increased
breathing rate
2.
Increased
tidal volume

Respiratory Responses – Neural &
Chemical Control
Breathing is a highly complex process
controlled by neural and chemical
factors
 Largely under involuntary control by
the respiratory centres of your brain
 Breathing involves two actions:
- inhalation (an active process)
- exhalation (a passive process)

Respiratory Responses – Neural &
Chemical Control
1. Stretch receptors in lungs 3. The respiratory centres are
detect increase in rate and responding to central nervous
depth of breathing
system and peripheral nervous
system information.
2. The respiratory centres
(the medulla and pons)
4. Other information comes from
send nerve impulses to the
chemorereceptors (i.e. within aortic
respiratory muscles that
arch and carotid bodies) and
controls breathing
mechanoreceptors
in
joints,
frequency and tidal volume tendons and active muscles that
each breath
assess movement and metabolic
status
2. Increased tidal volume



Tidal Volume is the
amount of air

breathed in and out in
each breath (approx
500cm3 at rest)

Only two-thirds
(350cm3) reaches the
alveoli where gaseous
exchange occurs.
During exercise, tidal volume increases to
allow more air to pass through the lungs
The volume of air passing through the
lungs each minute is know as the ‘minute
volume’ (breathing rate x tidal volume).
Tidal volume is elevated by both aerobic
and anaerobic exercise. During exercise,
oxygen depletion triggers a deeper
tidal volume to compensate
Respiratory responses
1. Increased breathing rate



A minor rise in breathing rate has been recorded
prior to exercise – this is know as ‘anticipatory rise’.
When exercise begins there is an immediate and
significant increase in breathing rate.
This is believed to be a result of receptors working
in both muscles and joints
Respiratory responses
1. Increased breathing rate



Muscles demand more O2
after changes in exercise
intensity
CO2 increase as result of
increased energy
production
Breathing rate increases to
satisfy these demands


The capillary network
surrounding the alveoli
expands.
This results in increased
blood flow to the lungs
and increased
pulmonary diffusion
Breathing
Rate
Breathing rate will
plateau if exercise
intensity remains
the same
If intensity continues to
rise breathing rate will
plateau when athlete
reaches their maximal
level for oxygen
consumption (Vo2 max)
Breathing rate increases
with exercise intensity as
more oxygen is required for
energy production
Anticipatory response
Exercise
Intensity
Respiratory responses
1. Increased breathing rate
Body


Heart
Lungs
Changes in the concentration
of CO2 and O2 in the blood
are detected by the
respiratory centre which
increases the rate of breathing
The intercostal muscles,
diaphragm and other muscle
which aid the expansion of the
thoracic cavity work harder to
further increase the expansion
during inhalation, to draw in
more air.
Cardiovascular responses
2. Activity response
Oxygen demand by muscles many times
greater during exercise than at rest
 Increased oxygen delivery accomplished by:
 Increase in heart rate – b.p.m. increase with
exercise intensity
 Increased cardiac output
 Redistribution of blood flow to skeletal
muscle

Recap
http://www.teachpe.com/cross/breathing_m
echanisms.htm
2. Activity response – Increased
Cardiac Output


Cardiac output (SV x HR) increased by:
Increase in heart rate
Increase in stroke volume
Oxygen uptake by the muscle also
increases as intensity increases
2. Activity response - Redistribution of
blood flow
Blood flow to working skeletal muscle
increased
 Blood flow to less active organs (liver,
kidneys, gastrointestinal tract)
decreased

Redistribution of blood flow during exercise
Rest
Heavy/intense exercise, short duration,
e.g. 400 m
Muscle
Heart muscle
GI tract
Kidneys
Bones
Brain
Skin
Cardiac output
25 litre/min
5 litre/min
16
Acute response to exercise
Cardiovascular responses:
 Increased heart rate x Increased stroke
volume → increased cardiac output
 Redistribution of the blood around the
body, 20% to skeletal muscle increases to
80–85% during exercise
17
Investigation into acute cardiovascular
responses
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20 minute Cardio session x2
Subject 1: 3 tier intensity – walk – Steady state jog
– run (6min intervals)
Measurements and results taken every 6 minutes
Subject 2: Interval training session – 3 minute jog, 1
minute sprint (4 minute intervals)
Measurements and results taken every 4 minutes
Heart Rate monitors required
Blood pressure monitors required
3. Increased Blood Pressure




BP is the pressure of blood against the walls of your
arteries.
Normal BP 120/80
Systolic BP – Highest pressure within bloodstream.
Occurs when the heart is in systole (contacting)
Diastolic BP – Lowest pressure within bloodstream.
Occurs when the heart is in dyastole (relaxing,
filling with blood)
3. Increased Blood Pressure




Oxygen consumption and HR increases in relation to
the intensity of the activity
Systolic pressure rises progressively why??
Diastolic pressure stays the same or decreases
slightly
Pulse rate rises and blood flow to muscles increases
Vasodilation & Vasoconstiction

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Vasodilation –
Vascular portion of active muscles increases through
dilation of arterioles.
Increased diameter of blood vessels results in
increased blood flow to muscles
Vasoconstriction –
Contraction of arterioles
Decreased diameter of blood vessels results in
reduced blood flow to the muscles
TASK

In small groups produce a poster presentation on an
elite athlete showing the acute cardiovascular
responses to their activity.
Session Outcomes




Explain the term ‘acute response’
Describe two acute responses of the cardiovascular
to exercise
Investigate acute responses during short term
exercise
Evaluate acute responses after short term exercise