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The Physiology of Training

Chapter 13. The Physiology of Training. Performance Effect on VO 2max and Strength. Principles of Training. Overload Training effect occurs when a system is exercised at a level beyond which it is normally accustomed Specificity Training effect is specific to the muscle fibers involved

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The Physiology of Training

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  1. Chapter 13 The Physiology of Training . Performance Effect on VO2max and Strength

  2. Principles of Training • Overload • Training effect occurs when a system is exercised at a level beyond which it is normally accustomed • Specificity • Training effect is specific to the muscle fibers involved • Type of exercise • Reversibility • Gains are lost when overload is removed

  3. Moffit’s corollary to Principles of Training • Consistency • Once in a while is better than nothing….. but just barely • Even if just a little overload, as long as there is consistency there will be positive changes

  4. Result of Endurance Training • Structural and biochemical changes in muscle •  Mitochondrial number •  Enzyme activity •  Capillary density

  5. Result of Endurance Training • Ability to perform repeated sub maximal muscle contractions • Ability to support aerobic energy production • For longer periods (duration) • At higher intensities (work capacity) • Higher maximal oxygen consumption (VO2max) .

  6. . What is VO2max? • Maximum capacity to use oxygen in the recycling of ATP • Factors Affecting: • Delivery of oxygen • Blood circulation • Extraction of oxygen • Unloading • Use in metabolism • Mitochondria

  7. . Calculation of VO2max . • Product of maximal cardiac output (Q) and arteriovenous difference (a-vO2) • a-vO2 difference • Represents amount of oxygen taken into muscle tissue • Known from PO2 in arterial and venous blood • Greater difference = more O2 extracted . VO2max = HRmax x SVmax x (a-vO2)max

  8. Questions: . • Can VO2max be improved? • How much can it be improved? • What change influences it the most?

  9. Answers: • Yes, it can be improved • It can be increased by up to 15% • Improvements in VO2max from: • 50% due to  a-vO2 difference • 50% due to  SV • Differences in VO2max in untrained • Due to differences in SVmax . .

  10. a-vO2 Difference and Increased VO2max . • Improved ability of the muscle to extract oxygen from the blood: • 1.  Muscle blood flow (delivery) •  Capillary density (delivery) • 2.  Mitochondial number

  11. . Stroke Volume and Increased VO2max • Increased SVmax •  Preload (EDV) •  Plasma volume •  Venous return •  Ventricular volume •  Afterload (TPR) •  Arterial constriction •  Maximal muscle blood flow with no change in mean arterial pressure •  Contractility

  12. Structural and Biochemical Adaptations to Endurance Training •  Mitochondrial number  •  Oxidative enzymes • Krebs cycle (citrate synthase) • Fatty acid availability (-oxidation) • Electron transport chain (cytochromes) •  NADH (shuttling system) • Change in type of LDH (pyruvate unchanged) • Adaptations quickly lost with detraining

  13. Influence of Mitochondrial Number on ADP Concentration and VO2 . • [ADP] stimulates mitochondrial ATP production • Increased mitochondrial number following training • Lower [ADP] needed to increase ATP production and VO2 • More ATP available sooner when trained .

  14. Effect of Exercise Intensity and Duration on Mitochondrial Enzymes • Citrate synthase (CS) • Marker of mitochondrial oxidative capacity • Light to moderate endurance training • Increased CS in high oxidative fibers (Type I and IIa) • Strenuous endurance training • Increased CS in low oxidative fibers (Type IIb)

  15. Biochemical Changes and FFA Oxidation • Increased mitochondrial number and capillary density • Increased capacity to transport FFA from plasma to cytoplasm to mitochondria • Increased enzymes of -oxidation • Increased rate of acetyl CoA formation • Increased FFA oxidation • Spares muscle glycogen and blood glucose

  16. LDH pyruvate + NADH lactate + NAD Blood *Lactate Concentration • Lactate production during exercise • Endurance training  production • FFA use instead of glycolysis • H isoform of LDH = low affinity for pyruvate •  removal • Malate-aspartate shuttle = NADH to mitochondria

  17. . Detraining and VO2max . • Decrease in VO2max with cessation of training •  SVmax •  maximal a-vO2 difference (Opposite of training effect)

  18. Detraining: Time Course of Changes in Mitochondrial Number: Study Results • About 50% of the increase in mitochondrial content was lost after one week of detraining • All of the adaptations were lost after five weeks of detraining • It took four weeks of retraining to regain the adaptations lost in the first week of detraining

  19. Time-course of Training/Detraining Mitochondrial Changes

  20. Time Course of Changes Associated With Detraining

  21. Physiological Effects of Strength Training • Neural factors • Increased ability to activate motor units - recruitment • Strength gains in initial 8-20 weeks • Muscular enlargement • Mainly due enlargement of fibers (hypertrophy) • More sarcomeres in parallel • More fluid within the cell • Long-term strength training

  22. Neural and Muscular Adaptations to Resistance Training

  23. Questions?

  24. End

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