1. Scott K. Powers Edward T. Howley Theory and Application to Fitness and Performance SEVENTH EDITION Chapter Copyright ©2009 The McGraw-Hill Companies, Inc. Permission required for reproduction or display outside of classroom use. Acid-Base Balance During Exercise

2. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Objectives 1.Define the terms acid, base, and pH. 2.Discuss the importance of acid-base regulation to exercise performance. 3.List principal intracellular and extracellular buffers. 4.Explain the role of respiration in the regulation of acid-base status during exercise. 5.Outline acid-base regulation during exercise. 6.Discuss the principal ways that hydrogen ions are produced during exercise.

3. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Outline  Acids, Bases, and pH  Hydrogen Ion Production During Exercise  Importance of Acid-Base Regulation During Exercise  Acid-Base Buffer Systems Intracellular Buffers Extracellular Buffers  Respiratory Influence on Acid- Base Balance  Regulation of Acid-Base Balance via the Kidneys  Regulation of Acid-Base Balance During Exercise

4. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Acids and Bases Acid –Molecule that can liberate H + Increases H + concentration in solution –Lactic acid is a strong acid Base –Molecule that is capable of combining with H + –Bicarbonate (HCO 3 – ) is a strong base Acids, Bases, and pH

5. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. pH Expression of H + solution in solution Negative logarithm of H + concentration pH of pure water Acids, Bases, and pH pH = –log 10 [H + ] pH (pure water) = –log 10 [H + ] = 7.0

6. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. pH of Blood Normal pH = 7.4±0.05 Acidosis pH < 7.4 Alkalosis pH > 7.4 Abnormal pH can disrupt normal body function and affect performance Survival range: 6.8–7.8 Acids, Bases, and pH

7. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. The pH Scale Acids, Bases, and pH Figure 11.1

8. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Acidosis and Alkalosis Acids, Bases, and pH Figure 11.2

9. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Clinical Applications 11.1 Conditions and Diseases That Promote Metabolic Acidosis or Alkalosis Metabolic acidosis –Gain in the amount of acid in the body –Long-term starvation Through production of ketoacids From fat metabolism –Uncontrolled diabetes Diabetic ketoacidosis Metabolic alkalosis –Loss of acids from the body –Severe vomiting –Kidney disease Acids, Bases, and pH

10. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. In Summary  Acids are defined as molecules that can liberate hydrogen ions, which increases the hydrogen ion concentration of an aqueous solution.  Bases are molecules that are capable of combining with hydrogen ions.  The concentration of hydrogen ions in a solution is quantified by pH units. The pH of a solution is defined as the negative logarithm of the hydrogen ion concentration: pH = –log 10 [H + ] Acids, Bases, and pH

11. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Sources of H + Ions During Exercise Volatile acids –Carbon dioxide End product of carbohydrate, fat, and protein metabolism Fixed acids –Sulfuric acid From metabolism of certain amino acids –Phosphoric acid From phospholipid and nucleic acid metabolism Organic acids –Lactic acid and acetoacetic acid From carbohydrate and fat metabolism CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 – Hydrogen Ion Production During Exercise

12. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Sources of Hydrogen Ions Due to Metabolic Processes Hydrogen Ion Production During Exercise Figure 11.3

13. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Popular Sports and Acid-Base Balance Hydrogen Ion Production During Exercise

14. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. A Closer Look 11.1 Sport and Exercise-Induced Disturbances in Muscle Acid-Base Balance Sports lasting ≥45 seconds can produce significant amounts of H + In many sports, risk of acid-base balance is related to effort of the competitor –Playing at 100% increases risk –Sprint to finish in distance event increases risk Acid-base disturbances can limit performance –Contributes to fatigue –Increasing blood buffering capacity may improve performance Hydrogen Ion Production During Exercise

15. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. In Summary  Metabolic acids can be subdivided into three major groups: (1) volatile acids (e.g., carbon dioxide), (2) fixed acids (e.g., sulfuric acid, phosphoric acid), and (3) organic acids (e.g., lactic acid). Hydrogen Ion Production During Exercise

16. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Importance of Acid-Base Regulation During Exercise Heavy exercise results in production of lactic acid Increased [H + ] can impair performance –Inhibits enzymes in aerobic and anaerobic ATP production –Hinders muscle contractile process by competing with Ca +2 for binding sites on troponin Importance of Acid-Base Regulation During Exercise

17. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. In Summary  Failure to maintain acid-base balance may impair performance by inhibiting metabolic pathways for the production of ATP or by interfering with the contractile process in the working muscle. Importance of Acid-Base Regulation During Exercise

18. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Acid-Base Buffer Systems Acid-base balance maintained by buffers –Release H + ions when pH is high –Accept H + ions when pH is low Intracellular buffers –Proteins –Phosphate groups –Bicarbonate Extracellular buffers –Bicarbonate –Hemoglobin –Blood proteins Acid-Base Buffer Systems

19. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Bicarbonate Buffering System Bicarbonate buffering system Henderson-Hasselbalch equation –Describes ability of bicarbonate-carbonic acid to act as buffer system CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 – Acid-Base Buffer Systems pH = pKa + log 10 (HCO 3 – / H 2 CO 3 )

20. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Acid-Base Buffer Systems

21. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. The Winning Edge 11.1 Ingestion of Sodium Buffers and Human Performance Acid-Base Buffer Systems Some studies show improved performance with ingestion of sodium buffers –Other studies show no improvement in performance Sodium Buffers –Sodium bicarbonate and sodium citrate –Can increase time to exhaustion during high- intensity exercise (80–120% VO 2 max) Considerations for use –Can cause nausea and vomiting Especially with sodium bicarbonate –Large doses can cause alkalosis –May be banned

22. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. In Summary  The body maintains acid-base homeostasis by buffer-control systems. A buffer resists pH change by removing hydrogen ions when the pH declines and by releasing hydrogen ions when the pH increases.  The principal intracellular buffers are proteins, phosphate groups, and bicarbonate. Primary extracellular buffers are bicarbonate, hemoglobin, and blood proteins. Acid-Base Buffer Systems

23. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Respiratory Influence on Acid- Base Balance Carbonic acid dissociation equation When pH decreases, [H + ] increases –Reaction moves to the left –CO 2 is “blown off” by the lungs, raising pH Respiratory Influence on Acid-Base Balance CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 –

24. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. In Summary  Respiratory control of acid-base balance involves the regulation on blood PCO 2. An increase in blood PCO 2 lowers pH, whereas a decrease in blood PCO 2 increases pH. Respiratory Influence on Acid-Base Balance

25. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Regulation of Acid-Base Balance via the Kidneys Important in long-term acid-base balance –Not significant in acid-base balance during exercise Regulate blood bicarbonate concentration –When blood pH decreases Reduced rate of bicarbonate excretion –When blood pH increases Increased rate of bicarbonate excretion Regulation of Acid-Base Balance via the Kidneys

26. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. In Summary  Although the kidneys play an important role in the long-term regulation of acid- base balance, the kidneys are not significant in the regulation of acid- base balance during exercise. Regulation of Acid-Base Balance via the Kidneys

27. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Regulation of Acid-Base Balance During Exercise Lactic acid production depends on: –Exercise intensity –Amount of muscle mass involved –Duration of exercise Blood pH –Declines with increasing intensity exercise Muscle pH –Declines more dramatically than blood pH Muscle has lower buffering capacity Regulation of Acid-Base Balance During Exercise

28. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Changes in Arterial Blood and Muscle pH During Exercise Regulation of Acid-Base Balance During Exercise Figure 11.4

29. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Regulation of Acid-Base Balance During Exercise Buffering of lactic acid in the muscle –60% through intracellular proteins –20–30% by muscle bicarbonate –10–20% from intracellular phosphate groups Buffering of lactic acid in the blood –Bicarbonate is major buffer Increases in lactic acid accompanied by decreases in bicarbonate and blood pH –Hemoglobin and blood proteins play minor role Regulation of Acid-Base Balance During Exercise

30. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Regulation of Acid-Base Balance During Exercise Figure 11.5 Changes in Blood Lactic Acid, HCO 3 –, and pH During Exercise

31. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Regulation of Acid-Base Balance During Exercise First line –Cellular buffers Proteins, bicarbonate, and phosphate groups –Blood buffers Bicarbonate, hemoglobin, and proteins Second line –Respiratory compensation Increased ventilation in response to increased H + concentration Regulation of Acid-Base Balance During Exercise

32. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Lines of Defense Against pH Change During Intense Exercise Regulation of Acid-Base Balance During Exercise Figure 11.6

33. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. In Summary  Figure 11.6 outlines the process of buffering exercise-induced acidosis.  The first line of defense against exercise-produced hydrogen ions is the chemical buffer systems of the intracellular compartment and the blood. These buffer systems act rapidly to convert strong acids into weak acids.  Intracellular buffering occurs with the aid of cellular proteins, bicarbonate, and phosphate groups. Regulation of Acid-Base Balance During Exercise

34. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. In Summary  Blood buffering of hydrogen ions occurs through bicarbonate, hemoglobin, and blood proteins, with bicarbonate playing the most important role.  The second line of defense against pH shift during exercise is respiratory compensation for metabolic acidosis. Regulation of Acid-Base Balance During Exercise

35. Chapter 11 Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved. Study Questions 1.Define the terms acid, base, buffer, acidosis, alkalosis, and pH. 2.Graph the pH scale. Label the pH values that represent normal arterial and intracellular pH. 3.List and briefly describe the major groups of acids formed by the body. 4.Why is the maintenance of acid-base homeostasis important to physical performance? 5.What are the principal intracellular and extracellular buffers? 6.Discuss respiratory compensation for metabolic acidosis. What would happen to blood pH if an individual began to hyperventilate at rest? Why? 7.Briefly, outline how the body resists pH change during exercise.