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

6. Examples of work (METS) Rest 1 Cycling <10 mph 6 Cycling >20mph 16 Running (10 min/mile)10 Running (6 min/mile)16 METS=metabolic equivalent tasks 1 MET=resting energy expenditure= 3.5 mlO 2  kg -1  min -1 = 1 Kcal  kg -1  min -1

7. aO 2 content=20 ml O 2 /100 ml blood vO 2 content=15 ml O 2 /100 ml blood CO=5 L/min

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

10. 80 120 Pressure (mmHg) systolic diastolic mean

12. Impact of Dynamic and Isometric Exercise on Arterial Blood Pressure DynamicStatic (isometric)

13. Comparison of BP Response Between Arm and Leg Ergometry

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

15. Arterial Baroreceptors Cardiovascular Physiology. Berne and Levy 1972

17. 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 – Increase in venous compliance

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

19. Baroreceptors adapt

20. 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

21. 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

22. 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. 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).

23. Oxygen Demand

24. aO 2 content=20 ml O 2 /100 ml blood vO 2 content=15 ml O 2 /100 ml blood CO=5 L/min

25. Meeting oxygen needs during exercise Fick equation VO 2 = Q  (Ca O 2 – Cv O 2 ) VO 2 = [HR  SV]  (Ca O 2 – Cv O 2 ) VO 2 = [BP  TPR]  (Ca O 2 – Cv O 2 )

26. Oxygen Extraction (E) Ca O 2 – Cv O 2 Ca O 2 Fick equation VO 2 = Q  (Ca O 2 – Cv O 2 ) VO 2 = Q  Ca O 2 x E E=

27. Arterial and venous oxygen during exercise O 2 Extraction =(19-12)/19 =0.33 O 2 Extraction =(19.5-2)/19.5 =0.90

28. Heart rate and stroke volume

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

33. Autonomic Nervous System NervesNeurotran smitter DistributionEffect SNSCervical Thoracic Pregang: ACH Postgang: NE Heart, Arteries & Most veins  1 (  HR)  1  2 PNSVagus and lumbar Pregang: ACH Post gang ACH Heart Vessels of Genitalia & colon  HR

34. The heart is under net vagal tone

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

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

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

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

41. Increase Preload

42. Increase Afterload

43. Increase Contractility

44. Stroke volume End diastolic volume – End-diastolic volume (Starling’s Law) End systolic volume – Afterload – Contractility

45. Time between beats

46. 2 Heart rate control during exercise by baroreceptors and skeletal muscle afferents. OLEARY, DONAL Medicine & Science in Sports & Exercise. 28(2):210-217, February 1996. Increase in heart rate decreases filling time Time between beats

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

48. J Appl Physiol 106: 486-493, 2009 Ο average-trained  endurance trained

49. Training and the CV system VO 2 = Q  CaO 2 x E = SV x HR x CaO 2 x E

50. Training Benefits seen after 3x week for 6 weeks 70% of max heart rate > 30 min/bout Maintenance 2x week but maintain intensity

51. College StudentsWorld Class Athletes ControlBedrestTrained VO 2 max (L/min)3.32.43.95.3 Max Ventilation (L/min) 191201197219 Arterial O 2 (mlO 2/ 100 ml blood) 21.920.520.822.4 Art-Ven O 2 (mlO 2/ 100 ml blood) 16.216.517.118 Max. cardiac Output (L/min) 2014.822.830.4 Max Heart rate (bpm) 192197190182 Stroke Volume (ml) 10474120167

52. Directly measured cardiac pressure–volume curves for athletes and non-athletic controls Note the marked improvement in both static and dynamic compliance in the endurance athletes Levine B D J Physiol 2008;586:25-34

53. Winder et al JAP 45:370,1978

54. Heart Adaptations to Training Endurance trained Sedentary Resistance trained

55. 1995 Marathon Training Data (females)

56. Adaptations to Training Resting bradycardia Increased stroke volume Increased cardiac size and compliance Increased blood volume Lower vascular resistance at any work load Improved flow distribution Improved oxygen extraction Improved heat tolerance

57. Training Heart Rates Low range – Between 60-70% of maximal heart rate – ~50-60% of VO 2 max High range – 90% of max heart rate – 85-90% of VO 2 max

58. Thermal stress and exercise

59. Impact of duration of exercise

60. Rowell LR Ann Rev Physiol 54:75,1976

61. Rowell LR. Ann Rev Physiol 54:75,1976