Chapter 10 Respiration During Exercise

1. Chapter 10Respiration During Exercise EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 5th edition Scott K. Powers & Edward T. Howley

2. Introduction • The Respiratory System • Provides a means of gas exchange between the environment and the body • Plays a role in the regulation of acid-base balance during exercise

3. Objectives • Explain the principle physiological function of the pulmonary system • Outline the major anatomical components of the respiratory system • List major muscles involved in inspiration and expiration, at rest and during exercise • Discuss the importance of matching blood flow to alveolar ventilation in the lung • Explain how gases are transported across the blood-gas interface in the lung

4. Objectives • Discuss the major transportation modes of O2 and CO2 in the blood • Discuss the effects of changes in temperature and pH on the oxygen-hemoglobin dissociation curve • Describe the ventilatory response to constant load, steady-state exercise

5. Objectives • Describe the ventilatory response to incremental exercise • Identify the location and function of chemoreceptors and mechanoreceptors that are thought to play a role in the regulation of breathing • Discuss the neural-humoral theory of respiratory control during exercise

6. Respiration 1. • Ventilation (breathing) and the exchange of gases (O2 and CO2) in the lungs 2. • Relates to O2 utilization and CO2 production by the tissues • This chapter is concerned with pulmonary respiration, and “respiration” will be used to mean such

7. Function of the Lungs • Primary purpose is to provide a means of gas exchange between the external environment and the body • ______________ refers to the mechanical process of moving air into and out of lungs • ___________ is the random movement of molecules from an area of high concentration to an area of lower concentration

8. Lungs (surface between external environment and blood) Alveolus [O2] [CO2] [O2] [O2] [CO2] [CO2] De-Oxygenated Blood Oxygenated Blood

9. ____________ zone Conducts air to respiratory zone _______, _______, and _______ air Components: Trachea Bronchial tree Bronchioles ____________ zone Exchange of gases between _______________ Components: Respiratory bronchioles Alveolar sacs Conducting and Respiratory Zones

11. Mechanics of Breathing • ____________ • Diaphragm pushes downward, lowering intrapulmonary pressure • ____________ • Diaphragm relaxes, raising intrapulmonary pressure • Resistance to airflow • Largely determined by airway ___________

12. The Mechanics of Inspiration and Expiration Fig 10.6

13. Muscles of Respiration Fig 10.7

15. Pulmonary Ventilation (V) • ____________ ventilation (VD) • “Unused” ventilation • Does not participate in gas exchange • Anatomical dead space: conducting zone • ________ ventilation (VA) • Volume of inspired gas that reaches the respiratory zone . V =

16. Pulmonary Volumes and Capacities • ____________ (TV) • Volume of air exhaled in one breath (L/breath) • ____________ (RR) • Number of breaths each minute (breaths/min) • ____________ (VE) VE = TV X RR ___ L/min = ___ L/breath X ___ breaths/min This is similar to Q = HR x SV!!!

17. PO2 = 0.2093 x 760 = 159 mmHg Partial Pressure of Gases______ Law • The total pressure of a gas mixture is equal to the sum of the pressure that each gas would exert independently • The partial pressure of oxygen (PO2) • Air is ______% oxygen • Expressed as a fraction: 0.2093 • Total pressure of air = 760 mmHg PCO2 = 0.0003 x 760 = 0.228 mmHg

18. V gas = x x ( - ) Diffusion of Gases______ law of diffusion • The rate of gas transfer (V gas) is proportional to the tissue area, the diffusion coefficient of the gas, and the difference in the partial pressure of the gas on the two sides of the tissue, and inversely proportional to the thickness. V gas = rate of diffusion D = diffusion coefficient of gas A = tissue area P1-P2 = difference in partial pressure T = tissue thickness

19. Partial Pressure and Gas Exchange Fig 10.11

20. Blood Flow to the Lung • Right ventricle • Output = ____ L/min • Pulmonary circulation = __________ circulation • Right ventricle isn’t as strong as left ventricle, but it doesn’t have as far to pump blood • When standing, most of the blood flow is to the _____ of the lung • Due to gravitational force Fig 10.13

21. O2 Transport in the Blood • Approximately 99% of O2 is transported in the blood bound to hemoglobin (Hb) • ____________: O2 bound to Hb • _______________: O2 not bound to Hb • Amount of O2 that can be transported per unit volume of blood is dependent on the ______________ of hemoglobin • Carrying capacity • ______ ml O2/L blood in males • ______ ml O2/L blood in females

22. O2 Transport in Blood • Normal Hb binds 1.34 ml O2/g • Males have ______ gHb/L of blood If 100% saturated, 150g Hb/L * 1.34ml O2/g = ~____ml O2/L • Females have _____ gHb/L of blood 130g Hb/L * 1.34ml O2/g = ~____ ml O2/L

23. Oxyhemoglobin Dissociation Curve Fig 10.15

24. O2-Hb Dissociation Curve: Effect of pH • Blood pH declines during heavy exercise • Results in a “________” shift of the curve • _______ effect • Favors “________” of O2 to the tissues Fig 10.16

25. O2-Hb Dissociation Curve: Effect of Temperature • Increased blood temperature results in a _______ Hb-O2 bond • _________ shift of curve • Easier “______” of O2 at tissues Fig 10.17

26. O2 Transport in Muscle • __________ (Mb) shuttles O2 from the cell membrane to the mitochondria • ________ affinity for O2 than hemoglobin • Even at low PO2 • Allows Mb to _______ O2

27. Dissociation Curves for Myoglobin and Hemoglobin Fig 10.18

28. CO2 Transport in Blood • Dissolved in plasma ( ___%) • Bound to Hb ( ___%) • Bicarbonate ( ___%) • CO2 + H2O  H2CO3  H+ + HCO3- • Also important for buffering ___

30. Exercise in a Hot Environment • During prolonged submaximal exercise: • Ventilation tends to drift upward • Little change in PCO2 • Higher ventilation not due to increased PCO2 Fig 10.22

31. Incremental Exercise • Linear increase in ventilation • Up to ~50-75% VO2max • Exponential increase beyond this point • _________________ (Tvent) • Inflection point where VE increases exponentially

32. Ventilatory Response to Exercise:Trained vs. Untrained • In the trained runner, • Decrease in arterial PO2 near exhaustion • pH maintained at a higher work rate • Tvent occurs at a higher work rate

33. Ventilatory Response to Exercise:Trained vs. Untrained Fig 10.23

34. Exercise-Induced Hypoxemia • 1980s: 40-50% of elite male endurance athletes were capable of developing • 1990s: 25-51% of elite female endurance athletes were also capable of developing • Causes: • _______________ mismatch • ________ limitations due to reduce time of RBC in pulmonary capillaries due to high cardiac outputs

35. Input to the Respiratory Control Centers • Input to the respiratory control center can be classified into 2 types: 1. (blood-borne) • Classified according to their location • __________ chemoreceptors • Located in the medulla • PCO2 and H+ concentration in cerebrospinal fluid • __________ chemoreceptors • Aortic and carotid bodies • PO2, PCO2, and H+ in blood 2. • From motor cortex or skeletal muscle

36. Effect of Arterial PCO2on Ventilation Fig 10.26

37. Effect of Arterial PO2on Ventilation Fig 10.27

38. Ventilatory Control During Exercise • Submaximal exercise • Linear increase due to: • Central command • Humoral chemoreceptors • Neural feedback

39. Ventilatory Control During Submaximal Exercise Fig 10.28

40. Effect of Training on Ventilation • Ventilation is lower at same work rate following training • May be due to lower blood lactic acid levels • Results in less feedback to stimulate breathing

41. Effects of Endurance Training on Ventilation During Exercise Fig 10.29

42. Do the Lungs Limit Exercise Performance? • Low-to-moderate intensity exercise • Pulmonary system not seen as a limitation • Maximal exercise • Not thought to be a limitation in healthy individuals at sea level • May be limiting in elite endurance athletes • New evidence that respiratory muscle fatigue does occur during high intensity exercise

43. Nasal Strips during Exercise??? • What is their purpose? • To hold the nostrils open >> Thus reduce nasal airway resistance • This would theoretically increase airflow to the lungs • No evidence to support increase pulmonary VE • Thus performance not improved in aerobic or anaerobic events • Placebo effect!!!