1. 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 CHAPTER 4

2. Acute Responses :

4. ACUTE RESPIRATORY RESPONSES

5. Acute Respiratory Responses Physiological Responses Outcome ↑Tidal Volume Increase O 2 uptake Increase removal of CO 2 Increased aerobic ATP production (can produce energy aerobically at a higher intensity) ↑ Respiratory Rate ↑ Ventilation ↑ Gas Exchange / Diffusion

6. Acute Respiratory Responses

7. ↑ 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

9. CARDIOVASCULAR RESPONSES

10. Acute Cardiovascular Responses Physiological Responses Outcome ↑Heart Rate ↑ O 2 transport and delivery ↑ removal of metabolic by products ↑ aerobic ATP production (can produce energy aerobically at a higher intensity) ↑ Stroke Volume ↑ Cardiac Output (Q) ↑ Blood flow to working muscles

11. 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

12. 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

13. 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 VO 2 max. Beyond this intensity, it is HR rather than SV that increases Q

14. Acute Cardiovascular Responses

19. Exam Question (VCAA 2011)

21. Acute Cardiovascular Responses Blood pressure Increases immediately in the transition from rest to exercise The extent of this increase depends on the exercise intensity

22. 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.

23. Acute Cardiovascular Responses

24. ↑ 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 H 2 O. Acute Cardiovascular Responses

26. MUSCULAR RESPONSES

27. Acute Muscular Responses Physiological Responses Outcome ↑ muscle recruitment↑ rate of ATP production ↑ fuel metabolism (therefore  fuel stores) ↑ rate of ATP production ↑ muscle temperature Body needs to ↑ blood flow to skin to regulate ↑ a-VO 2 difference ↑ O 2 extraction ↑ aerobic ATP production (can produce energy aerobically at a higher intensity)

28. 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.

29. Acute Muscular Responses

31. 90 second event vs. 30 minute event? Event 1 Event 2 Justification

32. ↑ Arteriovenous oxygen difference (a-vO 2 diff) The difference in oxygen between the arterioles and venules The greater the extraction of oxygen by working muscles, the greater the a-vO 2 diff Acute Muscular Responses

33. Acute Responses

35. Exam Question (VCAA 2011)