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© 2007 McGraw-Hill Higher Education. All Rights Reserved. Presentation revised and updated by Brian B. Parr, Ph.D. University of South Carolina Aiken Chapter.

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Presentation on theme: "© 2007 McGraw-Hill Higher Education. All Rights Reserved. Presentation revised and updated by Brian B. Parr, Ph.D. University of South Carolina Aiken Chapter."— Presentation transcript:

1 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Presentation revised and updated by Brian B. Parr, Ph.D. University of South Carolina Aiken Chapter 13 The Physiology of Training: Effect on VO 2 max, Performance, Homeostasis, and Strength EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6th edition Scott K. Powers & Edward T. Howley

2 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Objectives 1.Explain the basic principles of training: overload and specificity. 2.Contrast cross-sectional with longitudinal research studies. 3.Indicate the typical change in VO 2 max with endurance training programs, and the effect of the initial (pretraining) value on the magnitude of the increase. 4.State the typical VO 2 max values for various sedentary, active, and athletic populations, 5.State the formula for VO 2 max using heart rate, stroke volume, and the a-vO 2 difference; indicate which of the variables is most important in explaining the wide range of VO 2 max values in the population. 6.Discuss, using the variables identified in objective 5, how the increase in VO 2 max comes about for the sedentary subject who participates in an endurance training program.

3 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Objectives 7.Define preload, afterload, and contractility, and discuss the role of each in the increase in the maximal stroke volume that occurs with endurance training. 8.Describe the changes in muscle structure that are responsible for the increase in the maximal a-vO 2 difference with endurance training. 9.Describe the underlying causes for the decrease in VO 2 max that occurs with cessation of endurance training. 10.Describe how the capillary and mitochondrial changes that occur in muscle as a result of an endurance training program are related to the following adaptations to submaximal exercise: a lower O 2 deficit, an increased utilization of FFA and a sparing of blood glucose and muscle glycogen, a reduction in lactate and H + formation, and an increase in lactate removal.

4 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Objectives 11.Discuss how changes in “central command” and “peripheral feedback” following an endurance training program can lower the heart rate, ventilation, and catecholamine responses to a submaximal exercise bout. 12.Contrast the role of neural adaptations with hypertrophy in the increase in strength that occurs with resistance training.

5 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Exercise: A Challenge to Homeostasis Figure 13.1

6 © 2007 McGraw-Hill Higher Education. All Rights Reserved. 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: Muscle fibers involved Energy system involved (aerobic vs. anaerobic) Velocity of contraction Type of contraction (eccentric, concentric, isometric)  Reversibility –Gains are lost when overload is removed

7 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Research Designs to Study Training  Cross-sectional studies –Examine groups of differing physical activity at one time –Record differences between groups  Longitudinal studies –Examine groups before and after training –Record changes over time in the groups

8 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Endurance Training and VO 2max  Training to increase VO 2max –Large muscle groups, dynamic activity –20-60 min, 3-5 times/week, 50-85% VO 2max  Expected increases in VO 2max –Average = 15% –2-3% in those with high initial VO 2max –30–50% in those with low initial VO 2max  Genetic predisposition –Accounts for 40%-66% VO 2max –Prerequisite for VO 2max of 60–80 mlkg -1 min -1

9 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Range of VO 2max Values in the Population Table 13.1

10 © 2007 McGraw-Hill Higher Education. All Rights Reserved.  Product of maximal cardiac output and arteriovenous difference  Differences in VO 2max in different populations –Due to differences in SV max  Improvements in VO 2max –50% due to  SV –50% due to  a-vO 2 VO 2max = HR max x SV max x (a-vO 2 ) max Calculation of VO 2max

11 © 2007 McGraw-Hill Higher Education. All Rights Reserved.

12 Increased VO 2max With Training  Increased SV max –  Preload (EDV)  Plasma volume  Venous return  Ventricular volume –  Afterload (TPR)  Arterial constriction  Maximal muscle blood flow with no change in mean arterial pressure –  Contractility

13 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Factors Increasing Stroke Volume Figure 13.2

14 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Increased VO 2max With Training  a-vO 2max –  Muscle blood flow  SNS vasoconstriction –Improved ability of the muscle to extract oxygen from the blood  Capillary density  Mitochondial number

15 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Factors Causing Increased VO 2max Figure 13.3

16 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Detraining and VO 2max  Decrease in VO 2max with cessation of training –  SVmax Rapid loss of plasma volume –  Maximal a-vO 2 difference  Mitochondria  Oxidative capacity of muscle -  Type IIa fibers and  type IIx fibers

17 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Detraining and Changes in VO 2max and Cardiovascular Variables Figure 13.4

18 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Effects of Endurance Training on Performance  Maintenance of homeostasis –More rapid transition from rest to steady-state –Reduced reliance on glycogen stores –Cardiovascular and thermoregulatory adaptations  Neural and hormonal adaptations –Initial changes in performance  Structural and biochemical changes in muscle –  Mitochondrial number –  Capillary density

19 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Structural and Biochemical Adaptations to Endurance Training  Increased capillary density  Increased number of mitochondria   Increase in oxidative enzymes –Krebs cycle (citrate synthase) –Fatty acid (  -oxidation) cycle –Electron transport chain  Increased NADH shuttling system –NADH from cytoplasm to mitochondria  Change in type of LDH

20 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Changes in Oxidative Enzymes With Training Table 13.4

21 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Time Course of Training/Detraining Mitochondrial Changes  Training –Mitochondria double with five weeks of training  Detraining –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

22 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Time Course of Training/Detraining Mitochondrial Changes Figure 13.5

23 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Effect Intensity and Duration on Mitochondrial Adaptations  Citrate synthase (CS) –Marker of mitochondrial oxidative capacity  Light to moderate exercise training –Increased CS in high oxidative fibers Type I and IIa  Strenuous exercise training –Increased CS in low oxidative fibers –Type IIx

24 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Changes in Citrate Synthase Activity With Exercise Figure 13.6

25 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Biochemical Adaptations and the Oxygen Deficit  [ADP] stimulates mitochondrial ATP production  Increased mitochondrial number following training –Lower [ADP] needed to increase ATP production and VO 2  Oxygen deficit is lower following training –Same VO 2 at lower [ADP] –Energy requirement can be met by oxidative ATP production at the onset of exercise Faster rise in VO 2 curve and steady-state is reached earlier  Results in less lactic acid formation and less PC depletion

26 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Mitochondrial Number and ADP Concentration Needed to Increase VO 2 Figure 13.7

27 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Endurance Training Reduces the O 2 Deficit Figure 13.8

28 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Biochemical Adaptations and the Plasma Glucose Concentration  Increased utilization of fat and sparing of plasma glucose and muscle glycogen  Transport of FFA into the muscle –Increased capillary density Slower blood flow and greater FFA uptake  Transport of FFA from the cytoplasm to the mitochondria –Increased mitochondrial number and carnitine transferase  Mitochondrial oxidation of FFA –Increased enzymes of  -oxidation Increased rate of acetyl-CoA formation High citrate level inhibits PFK and glycolysis

29 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Effect of Mitochondria and Capillaries on Free-Fatty Acid and Glucose Utilization Figure 13.9

30 © 2007 McGraw-Hill Higher Education. All Rights Reserved.  Lactate production during exercise –Increased mitochondrial number Less carbohydrate utilization = less pyruvate formed –Increased NADH shuttles Less NADH available for lactic acid formation –Change in LDH type Heart form (H 4 ) has lower affinity for pyruvate = less lactic acid formation pyruvate + NADH lactate + NAD LDH Biochemical Adaptations and Blood pH M 4  M 3 H  M 2 H 2  MH 3  H 4

31 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Mitochondrial and Biochemical Adaptations and Blood pH Figure 13.10

32 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Biochemical Adaptations and Lactate Removal  Lactate removal –By nonworking muscle, liver, and kidneys –Gluconeogenesis in liver  Increased capillary density –Muscle can extract same O2 with lower blood flow –More blood flow to liver and kidney Increased lactate removal

33 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Biochemical Adaptations and Lactate Removal Figure 13.12

34 © 2007 McGraw-Hill Higher Education. All Rights Reserved. J-Shaped Relationship Between Exercise and URTI Figure 13.11

35 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Links Between Muscle and Systemic Physiology  Biochemical adaptations to training influence the physiological response to exercise –Sympathetic nervous system (  E/NE) –Cardiorespiratory system (  HR,  ventilation)  Due to: –Reduction in “feedback” from muscle chemoreceptors –Reduced number of motor units recruited  Demonstrated in one leg training studies –Lack of transfer of training effect to untrained leg

36 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Lack of Transfer of Training Effect Figure 13.13

37 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Peripheral and Central Control of Cardiorespiratory Responses  Peripheral feedback from working muscles –Group III and group IV nerve fibers Responsive to tension, temperature, and chemical changes Feed into cardiovascular control center  Central Command –Motor cortex, cerebellum, basal ganglia Recruitment of muscle fibers Stimulates cardiorespiratory control center

38 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Peripheral Control of Heart Rate, Ventilation, and Blood Flow Figure 13.14

39 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Central Control of Cardiorespiratory Responses Figure 13.15

40 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Physiological Effects of Strength Training  Strength training results in increased muscle size and strength  Neural factors –Increased ability to activate motor units –Strength gains in initial 8-20 weeks  Muscular enlargement –Mainly due enlargement of fibers Hypertrophy –May be due to increased number of fibers Hyperplasia –Long-term strength training

41 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Neural and Muscular Adaptations to Resistance Training Figure 13.16

42 © 2007 McGraw-Hill Higher Education. All Rights Reserved. Training to Improve Muscular Strength  Traditional training programs –Variations in intensity, sets, and repetitions  Periodization –Volume and intensity of training varied over time –More effective than non-periodized training for improving strength and endurance  Concurrent strength and endurance training –Adaptations may or may not interfere with each other Depends on intensity, volume, and frequency of training


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