Functional Capacity of the Cardiovascular System: Cardiac Output and Oxygen Transport

1. Chapter 17 Functional Capacity of the Cardiovascular System McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

2. Cardiac Output • Cardiac output (Q) = HR × SV • Methods of Measuring Q • Direct Fick • Indicator dilution • CO2 rebreathing McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

3. Direct Fick Method Q = O2 mL · min−1 a- O2 difference McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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5. Indicator Dilution Method Q = Quantity of dye injected Average dye concentration blood ×Duration of curve for duration of curve McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

6. CO2 Rebreathing Method Q = CO2× 100 -aCO2 difference McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

7. Cardiac Output at Rest • Values vary depending upon emotional state. • Average male ~5 L · min-1 • Average female ~4 L · min-1 McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

8. Untrained Characteristics of Q • HR ~ 70 BPM • SV ~ 71.4 mL • Average women ~25% lower due to smaller size McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

9. Endurance Athletes • Characteristics of Q • HR ~ 50 BPM • SV ~ 100 mL • Mechanisms • Increased vagal tone w/decreased sympathetic drive • Increased blood volume • Increased myocardial contractility and compliance of left ventricle McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

10. Cardiac Output During Exercise • Q increases rapidly during transition from rest to exercise. • Q at max exercise increases up to 4 times. Q HR SV Untrained 22 L 195 113 mL Trained 35 L 195 179 mL McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

11. Stroke Volume: Diastolic Filling vs. Systole Emptying • Mechanisms for increased SV with training • Increased blood volume – increase diastolic filling • Increased preload – Starling’s Law of the Heart • Increased Contractility – greater systolic emptying McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

12. Cardiovascular Drift • Results from • Dehydration • Reduction in SV • HR drifts upward to maintain same Q McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

13. Cardiac Output Distribution • Blood flows to tissues in proportion to their metabolic activity. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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16. Cardiac Output and Oxygen Transport Rest Q = 5 L · min-1 O2 transport = 1,000 mL – 200 mL/L blood McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

17. Exercise • Max Q averages ~ 16 L · min-1 • O2 transport = 200 mL/L blood • Result • 3200 mL O2 • Training enables Q to increase up to 40 L · min-1, increasing O2 transport up to 8,000 mL. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

18. Close Association BetweenMax Q and O2max • An almost proportionate increase in max Q accompanies increases in O2max with training. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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20. Cardiac Output Differences: Men, Women, and Children • Women have a 10% lower hemoglobin level than men. • Result is a 5 – 10% increase in Q at any submax level of O2 consumption • Children have higher HR • Result is smaller Q, expanded a- O2 McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

21. O2 Extraction: The a- O2 Difference • O2 consumption increases during exercise. • Increases Q • Increases extraction of O2 by tissues • O2 = Q x a- O2 difference McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

22. a- O2 Difference during Rest • 20 mL O2 ·dL-1 arterial blood • 15 mL O2 ·dL-1 venous blood • 5 mL a- O2diff McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

23. a- O2 Difference during Exercise • 20 mL O2 ·dL-1 arterial blood • 5 – 15 mL O2 ·dL-1 venous blood • Up to a threefold increase in O2 extraction McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

24. Severe Heart Disease • Exhibit low ability to improve Q or SV • Skeletal muscle adaptations allow for increased O2 extraction. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

25. Factors Affecting the a- O2 Differences • Redistribution of flow to active tissues during exercise • Increased capillary density due to training increases surface area and O2 extraction • Increased number and size of mitochondria • Increased oxidative enzymes • Vascular and metabolic improvements McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

26. Cardiovascular Adjustments toUpper-Body Exercise • Max O2 consumption • Upper-body exercise results in max O2 consumption ~20 – 30% lower than lower-body exercise. • Higher O2 consumption for a given submax workload • Lower mechanical efficiency • Muscular effort to stabilize torso McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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28. Physiologic Response • Submaximal arm exercise produces > HR > Pulmonary ventilations > RPE > BP response than comparable leg exercise McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

29. Physiologic Response • Exercise prescription for arm exercise should not be based on values obtained from lower-body exercises. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition