1. Cardiovascular System Lecture 5 (part I-II) September 28, 2005 October 5, 2005 EXS 558 Dr. Moran

2. Major Cardiovascular Functions  Delivery (e.g., oxygen and nutrients)   Transportation (e.g., hormones)   Prevention (e.g., infection—immune function)

3. Just Some Facts For an average person the heart pumps ~5L/min With exercise programs the heart (cardiac muscle) can adapt as well

4. Heart

5. Myocardium – Cardiac Muscle  Thickness varies directly with stress placed on chamber walls.   With vigorous exercise, the left ventricle size increases. 

6. Heart Function At rest, the heart spends most of its time filling (60% - diastole) than expelling (40% - systole) Following systole, the AV valves rapidly open and fill the ventricles up to 70-80% The middle 1/3 of diastole has little filling and is known as diastasis

7. Stroke Volume & Cardiac Output Stroke Volume (SV)   End-systolic volume (ESV)—volume of blood in ventricle after contraction  SV = EDV – ESV  Volume of blood pumped per contraction  Cardiac Output (Q).  Q = HR  SV  Varies considerably between people  Trained athletes have lower resting HR and higher SV (Table 4.1).

8. Ejection Fraction  Proportion of blood pumped out of the left ventricle each beat   Averages 60% at rest 

9. Calculation of SV, EF, and Q

10. Vascular System  Arteries  Arterioles  Capillaries   Creates a large surface area ideal for gas exchange  Venules  Veins Blood Flow controlled by the autonomic nervous system During REST  During EXERCISE 

12. Muscle Pump  Blood distribution matched to overall metabolic demands  Autoregulation—  Extrinsic neural control— sympathetic nerves within walls of vessels are stimulated causing vessels to constrict 

13. Blood Pressure  Systolic blood pressure (SBP: s=squeeze) is the highest pressure and diastolic blood pressure (DBP) is the lowest pressure   MAP = DBP + [0.333  (SBP – DBP)] 

14. Review  Blood returns to the heart with the help of breathing, the muscle pump, and valves in the veins.  Vascular System  Autoregulation controls blood flow by vasodilation in response to local chemical changes in an area. (continued)

15. Review (continued)  Extrinsic neural factors control blood flow primarily by vasoconstriction.   Mean arterial pressure (MAP) is the average pressure on the arterial walls.

16. Blood Functions  Transports gas, nutrients, and wastes   Buffers and balances acid base

17. Blood Volume Composition

18. Blood Formed Elements & Hematocrit Blood formed elements  White blood cells—protect body from disease organisms   Red blood cells—carry oxygen to tissues with the help of hemoglobin Hematocrit  Ratio of formed elements to the total blood volume

19. Oxygen Transport Oxygen transported in blood combined to hemoglobin (98%) or dissolved in plasma (2%) Oxygen saturation affected by: 1.) 2.) 3.)

20. Bohr Effect

21. Erythropoietin (EPO) Protein hormone produced by kidney Medically used to treat anemia (chronic kidney failure) Increase oxygen carrying capacity of blood “Sludging” of blood VERY dangerous

22. Cardiovascular Response to Acute Exercise   All result in allowing the body to efficiently meet the increased demands placed on it.  Heart rate (HR) increases as exercise intensity increases up to maximal heart rate..   Increases in HR and SV during exercise cause cardiac output (Q) to increase..

23. Heart Rate During Exercise Initial increase b/c of withdrawal of parasympathetic input Feedback from peripheral mechanical and chemical receptors

24. Stroke Volume During Exercise Stroke volume changes are because of an increase in EDV Suctioning Mechanism: Frank-Starling Mechanism : with a greater volume of blood returning to the heart the ventricles become stretched and respond with a more powerful contraction

25. Cardiac Drift Increase in HR and decrease in SV Reason: greater % of blood flowing to skin to dissipate heat  lower EDV causes an increased HR

26. Arteriovenous Oxygen Difference Rest  25% of O 2 extracted from blood Exercise  up to 75% of O 2 extracted from blood (used by exercising muscles) Fick Equation:

27. Cardiovascular Response to Training Cardiac Output Heart Rate Cardiac Morphology Table 4.2 (p. 52)

28. Cardiac Output VO 2 max increases due to 1.) Improved oxygen extraction 2.) Increased cardiac output 3.) Max HR NOT affected from training

29. Stroke Volume Endurance-trained athletes have 60% greater SV Enlarged left ventricular chamber (eccentric hypertrophy)

30. Stroke Volume & Training

31. Changes in EDV, ESV, EF

32. Heart Rate Decrease in resting HR  Highly trained endurance athletes may have resting heart rates of 30 to 40 beats/min 

33. Heart Rate Recovery   With training, heart rate returns to resting level more quickly after exercise    Conditions such as altitude or heat can affect it

34. Heart Rate Recovery (continued)

35. Blood Pressure In hypertensive individuals, endurance exercise reduces both systolic and diastolic blood pressure (3-5x week; 30 min) Conflicting results from the result of resistance training 

36. Blood Flow Increases With Training  Increased capillarization of trained muscles (higher capillary-to-fiber ratio)   More effective blood redistribution—blood goes where it is needed 

37. Blood Volume and Training  Endurance training, especially intense training, increases blood volume.   Red blood cell volume increases, but increase in plasma volume is higher; thus, hematocrit decreases.   Changes in plasma volume are highly correlated with changes in SV and VO 2 max..

38. Blood Volume and Training

39. Cardiac Morphology Law of LaPlace: ventricular wall pressure is proportional to pressure and the radius of curvature (Ford 1976) Adaptations from Exercise Programs Endurance Athletes Greater than normal left ventricular internal diameter Resistance Athletes Left ventricular mass 45% greater than age-matched sedentary controls (Fleck 1988)

40. Differences in Heart Size Intraventricular septal thickness

41. The effect of acute aerobic exercise on stress related blood pressure responses: A systematic review and meta-analysis Hamer et al. (2005) Left Ventricular Mass Index and Sports: the influence of different sports activities and arterial blood pressure Cubero et al. (2000)

42. Echocardiograph (ultrasound)

43. Research Design Cross Sectional collected all at the same time (“snapshot”) Randomized Controlled Trial Two groups Treatment group  receives the treatment under investigation, Control group 

44. VO 2 Max Testing Depends on testing protocol Triathletes cycling ergometer protocol will be 3-6% less than that seen in treadmill running, while swimming is 13-18% less (O'Toole and Douglas, 1995)