1. THE PHYSIOLOGY OF FITNESS
The body’s response to acute exercise
Part Two: Respiratory Response

2. 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

3. 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

4. Responses to physical activity
Respiratory responses:
Increased breathing rate
Increased tidal volume

5. 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)

6. Respiratory Responses – Neural & Chemical Control
1. Stretch receptors in lungs detect increase in rate and depth of breathing
2. The respiratory centres (the medulla and pons) send nerve impulses to the respiratory muscles that controls breathing frequency and tidal volume each breath
3. The respiratory centres are responding to central nervous system and peripheral nervous system information.
4. Other information comes from chemorereceptors (i.e. within aortic arch and carotid bodies) and mechanoreceptors in joints, tendons and active muscles that assess movement and metabolic status

7. 2. Increased tidal volume
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
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.

8. 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

9. 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

10. 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
Exercise Intensity
Anticipatory response

11. Respiratory responses 1. Increased breathing rate
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.
Body
Heart
Lungs

12. 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

13. Recap

14. 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

15. 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

16. Redistribution of blood flow during exercise
Heavy/intense exercise, short duration, e.g. 400 m
Rest
Heart muscle
GI tract
Kidneys
Bones
Brain
Skin
Muscle
Cardiac output
5 litre/min
25 litre/min

17. 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

18. Investigation into acute cardiovascular responses
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

19. 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)

20. 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

21. Vasodilation & Vasoconstiction
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

22. TASK
In small groups produce a poster presentation on an elite athlete showing the acute cardiovascular responses to their activity.

23. 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