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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. Presentation revised and updated by Brian B. Parr, Ph.D.

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chapter 13 the physiology of training effect on vo 2 max performance homeostasis and strength

Chapter 13The Physiology of Training: Effect on VO2 max, Performance, Homeostasis, and Strength

EXERCISE PHYSIOLOGY

Theory and Application to Fitness and Performance, 6th edition

Scott K. Powers & Edward T. Howley

Presentation revised and updated by

Brian B. Parr, Ph.D.

University of South Carolina Aiken

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

objectives
Objectives
  • Explain the basic principles of training: overload and specificity.
  • Contrast cross-sectional with longitudinal research studies.
  • Indicate the typical change in VO2 max with endurance training programs, and the effect of the initial (pretraining) value on the magnitude of the increase.
  • State the typical VO2 max values for various sedentary, active, and athletic populations,
  • State the formula for VO2 max using heart rate, stroke volume, and the a-vO2 difference; indicate which of the variables is most important in explaining the wide range of VO2 max values in the population.
  • Discuss, using the variables identified in objective 5, how the increase in VO2 max comes about for the sedentary subject who participates in an endurance training program.

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

objectives3
Objectives
  • Define preload, afterload, and contractility, and discuss the role of each in the increase in the maximal stroke volume that occurs with endurance training.
  • Describe the changes in muscle structure that are responsible for the increase in the maximal a-vO2 difference with endurance training.
  • Describe the underlying causes for the decrease in VO2 max that occurs with cessation of endurance training.
  • 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 O2 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.

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

objectives4
Objectives
  • 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.
  • Contrast the role of neural adaptations with hypertrophy in the increase in strength that occurs with resistance training.

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

exercise a challenge to homeostasis
Exercise: A Challenge to Homeostasis

Figure 13.1

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

principles of training
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

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

research designs to study training
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

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

endurance training and vo 2max
Endurance Training and VO2max
  • Training to increase VO2max
    • Large muscle groups, dynamic activity
    • 20-60 min, 3-5 times/week, 50-85% VO2max
  • Expected increases in VO2max
    • Average = 15%
    • 2-3% in those with high initial VO2max
    • 30–50% in those with low initial VO2max
  • Genetic predisposition
    • Accounts for 40%-66% VO2max
    • Prerequisite for VO2max of 60–80 ml•kg-1•min-1

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

range of vo 2max values in the population
Range of VO2max Values in the Population

Table 13.1

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

calculation of vo 2max
Calculation of VO2max
  • Product of maximal cardiac output and arteriovenous difference
  • Differences in VO2max in different populations
    • Due to differences in SVmax
  • Improvements in VO2max
    • 50% due to SV
    • 50% due to a-vO2

VO2max = HRmax x SVmax x (a-vO2)max

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

increased vo 2max with training
Increased VO2max With Training
  • 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

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

factors increasing stroke volume
Factors Increasing Stroke Volume

Figure 13.2

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

increased vo 2max with training14
Increased VO2max With Training
  • a-vO2max
    •  Muscle blood flow
      •  SNS vasoconstriction
    • Improved ability of the muscle to extract oxygen from the blood
      •  Capillary density
      •  Mitochondial number

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

factors causing increased vo 2max
Factors Causing Increased VO2max

Figure 13.3

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

detraining and vo 2max
Detraining and VO2max
  • Decrease in VO2max with cessation of training
    •  SVmax
      • Rapid loss of plasma volume
    •  Maximal a-vO2 difference
      •  Mitochondria
      •  Oxidative capacity of muscle
        •  Type IIa fibers and  type IIx fibers

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

detraining and changes in vo 2max and cardiovascular variables
Detraining and Changes in VO2max and Cardiovascular Variables

Figure 13.4

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

effects of endurance training on performance
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

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

structural and biochemical adaptations to endurance training
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

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

changes in oxidative enzymes with training
Changes in Oxidative Enzymes With Training

Table 13.4

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

time course of training detraining mitochondrial changes
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

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

time course of training detraining mitochondrial changes22
Time Course of Training/Detraining Mitochondrial Changes

Figure 13.5

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

effect intensity and duration on mitochondrial adaptations
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

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

changes in citrate synthase activity with exercise
Changes in Citrate Synthase Activity With Exercise

Figure 13.6

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

biochemical adaptations and the oxygen deficit
Biochemical Adaptations and the Oxygen Deficit
  • [ADP] stimulates mitochondrial ATP production
  • Increased mitochondrial number following training
    • Lower [ADP] needed to increase ATP production and VO2
  • Oxygen deficit is lower following training
    • Same VO2 at lower [ADP]
    • Energy requirement can be met by oxidative ATP production at the onset of exercise
      • Faster rise in VO2 curve and steady-state is reached earlier
  • Results in less lactic acid formation and less PC depletion

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

mitochondrial number and adp concentration needed to increase vo 2
Mitochondrial Number and ADP Concentration Needed to Increase VO2

Figure 13.7

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

endurance training reduces the o 2 deficit
Endurance Training Reduces the O2 Deficit

Figure 13.8

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

biochemical adaptations and the plasma glucose concentration
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

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

effect of mitochondria and capillaries on free fatty acid and glucose utilization
Effect of Mitochondria and Capillaries on Free-Fatty Acid and Glucose Utilization

Figure 13.9

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

biochemical adaptations and blood ph

LDH

pyruvate + NADH

lactate + NAD

Biochemical Adaptations and Blood pH
  • 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 (H4) has lower affinity for pyruvate = less lactic acid formation

M4 M3H  M2H2  MH3  H4

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

mitochondrial and biochemical adaptations and blood ph
Mitochondrial and Biochemical Adaptations and Blood pH

Figure 13.10

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

biochemical adaptations and lactate removal
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

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

biochemical adaptations and lactate removal33
Biochemical Adaptations and Lactate Removal

Figure 13.12

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

j shaped relationship between exercise and urti
J-Shaped Relationship Between Exercise and URTI

Figure 13.11

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

links between muscle and systemic physiology
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

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

lack of transfer of training effect
Lack of Transfer of Training Effect

Figure 13.13

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

peripheral and central control of cardiorespiratory responses
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

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

peripheral control of heart rate ventilation and blood flow
Peripheral Control of Heart Rate, Ventilation, and Blood Flow

Figure 13.14

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

central control of cardiorespiratory responses
Central Control of Cardiorespiratory Responses

Figure 13.15

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

physiological effects of strength training
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

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

neural and muscular adaptations to resistance training
Neural and Muscular Adaptations to Resistance Training

Figure 13.16

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

training to improve muscular strength
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

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