CHAPTER 4
Acute Responses to Exercise
Key Knowledge 2.1: Functions responsible for short term (acute) responses to
physical activity in the cardiovascular, respiratory and muscular systems
Acute Responses :
Acute Responses :
ACUTE RESPIRATORY RESPONSES
Acute Respiratory Responses
Physiological Responses
Outcome
↑Tidal Volume
Increase O2 uptake
↑ Respiratory Rate
↑ Ventilation
↑ Gas Exchange / Diffusion
Increase removal of CO2
Increased aerobic ATP production
(can produce energy aerobically at a higher
intensity)
Acute Respiratory Responses
Acute Respiratory Responses
↑ Gas Exchange / Diffusion
Oxygen/Carbon Dioxide move from areas of high pressure to areas of low pressure.
Lungs
•oxygen from alveoli to capillary
•carbon dioxide from capillary to alveoli
Muscles (opposite concentrations to lungs)
•oxygen from capillary to muscles
•carbon dioxide from muscles to capillary
Acute Respiratory Responses
CARDIOVASCULAR RESPONSES
Acute Cardiovascular Responses
Physiological Responses
Outcome
↑Heart Rate
↑ O2 transport and delivery
↑ Stroke Volume
↑ Cardiac Output (Q)
↑ Blood flow to working
muscles
↑ removal of metabolic by products
↑ aerobic ATP production
(can produce energy aerobically at a higher
intensity)
Acute Cardiovascular Responses
Heart rate
• Immediately before an exercise effort or race it is normal to experience an
anticipatory rise in heart rate.
• Linear relationship between intensity and heart rate
Acute Cardiovascular Responses
Stroke volume
• the left ventricle will also eject a greater volume of blood with each beat to
assist in meeting oxygen demands
• Stroke Volume will plateau at ‘submaximal intensities’ for non elite athletes
Acute Cardiovascular Responses
Cardiac output
Q = SV X HR
• As intensity increases Q increases in a linear relationship
• Increases in Q arise from a rapid rise in both SV and HR, until an
intensity of approximately 60 per cent VO2max.
• Beyond this intensity, it is HR rather than SV that increases Q
Acute Cardiovascular Responses
Acute Cardiovascular Responses
Acute Cardiovascular Responses
Acute Cardiovascular Responses
Acute Cardiovascular Responses
Exam Question (VCAA 2011)
Exam Question (VCAA 2011)
Acute Cardiovascular Responses
Blood pressure
• Increases immediately in the transition from rest to exercise
• The extent of this increase depends on the exercise intensity
Acute Cardiovascular Responses
Redistribution of blood flow
• Immediately after the onset of exercise there is a redistribution of
blood flow throughout the body to meet the energy demands of
active muscle.
• Specifically, an increase in blood flow to the active muscles and a
reduction in blood flow to the organs occurs to meet the greater
oxygen and nutrient demands.
Acute Cardiovascular Responses
Acute Cardiovascular Responses
↑ Blood pressure
(mainly systolic) affected by stroke volume increase
↑ Venous return to heart
(assisted by muscle pump, respiratory pump and venoconstriction –5 times as
much blood compared to rest)
↓ Blood volume
(plasma loss) caused mainly by decrease in plasma volume which is mainly due to
a loss in H2O.
MUSCULAR RESPONSES
Acute Muscular Responses
Physiological Responses
Outcome
↑ muscle recruitment
↑ rate of ATP production
↑ fuel metabolism
(therefore  fuel stores)
↑ rate of ATP production
↑ muscle temperature
↑ a-VO2 difference
Body needs to ↑ blood flow to skin to
regulate
↑ O2 extraction
↑ aerobic ATP production
(can produce energy aerobically at a higher
intensity)
Acute Muscular Responses
Muscle Fibre Types
• Type I fibres are more efficient at
using oxygen to generate ATP for
continuous exercise requiring
muscle contractions to occur for
an extended time.
• These fibres fire at a slower rate
than Type II fibres and have
greater
fatigue
resistance,
proving valuable to endurance
performance in distance running,
swimming and cycling.
• Type II fibres are capable of
greater force production and
contract at a faster rate. This
makes them advantageous for
performance in strength, speed
and power events.
Acute Muscular Responses
Muscle Fuel Concentration 60 min run
30
25
20
15
10
5
0
Slow Twitch
Fast Twitch
Glycogen (mol/g) -pre
Glycogen (mol/g) - post
Acute Muscular Responses
Muscle Substrate
120
100
% fuel in muscle
80
60
40
20
0
% Fuel Substrate - pre
% Fuel Substrate - post
% Fuel Substrate - pre
Event 1
% Fuel Substrate - post
Event 2
Slow Twitch
Fast Twitch
90 second event vs. 30 minute event?
Event 2
Event 1
Justification
Justification
Acute Muscular Responses
↑ Arteriovenous oxygen difference (a-vO2 diff)
The difference in oxygen between the arterioles and venules
The greater the extraction of oxygen by working muscles, the greater the a-vO2 diff
Acute Responses
Acute Responses
Exam Question (VCAA 2011)
Exam Question (VCAA 2011)