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Cardiovascular response to exercise

Cardiovascular response to exercise. The Heart. Outline. General cardiac responses to exercise Control of heart rate Control of stroke volume Blood pressure Distribution of blood flow Barroreceptors Adaptations to training Impact of the environment. Examples of work (METS).

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Cardiovascular response to exercise

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  1. Cardiovascular response to exercise The Heart

  2. Outline • General cardiac responses to exercise • Control of heart rate • Control of stroke volume • Blood pressure • Distribution of blood flow • Barroreceptors • Adaptations to training • Impact of the environment

  3. Examples of work (METS) • Rest 1 • Cycling <10 mph 6 • Cycling >20 mph 16 • Running (10 min/mile) 10 • Running (6 min/mile) 16 METS=metabolic equivalent tasks 1 MET=resting energy expenditure= 3.5 mlO2kg-1 min-1= 1 Kcalkg-1 min-1

  4. O2 CO=5 L/min aO2 content=20 ml O2/100 ml blood vO2 content=15 ml O2/100 ml blood

  5. Effects of Exercise on Blood Pressure MABP-RAP = CO  TPR

  6. 120 80 systolic Pressure (mmHg) mean diastolic

  7. Impact of Dynamic and Isometric Exercise on Arterial Blood Pressure Dynamic Static (isometric)

  8. Comparison of BP Response Between Arm and Leg Ergometry

  9. Why is blood pressure going up? I thought we had sensors that control blood pressure.

  10. Arterial Baroreceptors Cardiovascular Physiology. Berne and Levy 1972

  11. Activation of Barroreceptor reflex Response to an increase in arterial pressure • Withdrawal of sympathetic tone • Activation of parasympathetic tone • Results: • Decrease heart rate and contractility • Arterial vasodilation • Increasein venous compliance

  12. Afferent nerve firing responds to absolute pressure and rate of change in pressure

  13. Baroreceptors adapt

  14. Afferent and efferent neural baroreflex responses Arterial Baroreflex Control of the Peripheral Vasculature in Humans: Rest and Exercise. FADEL, PAUL Medicine & Science in Sports & Exercise. 40(12):2055-2062, December 2008

  15. Afferent and efferent neural baroreflex responses to the application of neck pressure (NP) and neck suction (NS) Arterial Baroreflex Control of the Peripheral Vasculature in Humans: Rest and Exercise. FADEL, PAUL Medicine & Science in Sports & Exercise. 40(12):2055-2062, December 2008

  16. Schematic illustration of the effect of exercise on arterial baroreflex control of heart rate. Exercise resets the relationship between arterial pressure and heart rate upward and to the right (OP = hypothetical arterial baroreflex operating point). 3 Heart rate control during exercise by baroreceptors and skeletal muscle afferents. OLEARY, DONAL Medicine & Science in Sports & Exercise. 28(2):210-217, February 1996.

  17. Oxygen Demand

  18. O2 CO=5 L/min aO2 content=20 ml O2/100 ml blood vO2 content=15 ml O2/100 ml blood

  19. Meeting oxygen needs during exercise Fick equation VO2 = Q (CaO2 – CvO2) VO2 = [HR SV] (CaO2 – CvO2) VO2 = [BP TPR] (CaO2 – CvO2)

  20. Oxygen Extraction (E) Fick equation VO2 = Q  (CaO2 – CvO2) CaO2 – CvO2 CaO2 E= VO2= Q  CaO2 x E

  21. Arterial and venous oxygen during exercise O2Extraction =(19-12)/19 =0.33 O2 Extraction =(19.5-2)/19.5 =0.90

  22. Heart rate and stroke volume

  23. Heart rate Estimate Maximal heart rate =208-0.7 x (age year) =208-0.7x54=170 bpm

  24. Autonomic Nervous System

  25. The heart is under net vagal tone

  26. Epinephrine • Source: Adrenal medulla • Increase heart rate and contractility (1), • low concentrations vasodilation (2) • high concentrations vasoconstriction (1), decrease venous compliance (1)

  27. Norepinephrine • Source: Adrenal medulla • Increase heart rate and contractility (1), • Limited effect on 2 • At all concentrations vasoconstriction (1), decrease venous compliance (1)

  28. Determinants of Cardiac Output • Heart rate • Stroke volume • Ventricular end-diastolic volume • Contractility • Afterload (aortic pressure)

  29. Venus Blood Return to Heart • muscle pump • one-way venous valves • breathing Return of blood to heart

  30. Increase Preload

  31. Increase Afterload

  32. Increase Contractility

  33. Stroke volume • End diastolic volume • End-diastolic volume (Starling’s Law) • End systolic volume • Afterload • Contractility

  34. Time between beats

  35. Increase in heart rate decreases filling time Time between beats Heart rate control during exercise by baroreceptors and skeletal muscle afferents. OLEARY, DONAL Medicine & Science in Sports & Exercise. 28(2):210-217, February 1996. 2

  36. What would happen if you could not increase adrenergic tone to the heart during exercise? Metaprolol= 1 antagonist

  37. Οaverage-trained  endurance trained J Appl Physiol 106: 486-493, 2009

  38. Training and the CV system VO2= Q  CaO2 x E = SV x HR x CaO2 x E

  39. Training

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