Exercise metabolism

1
Exercise metabolism

• ATP production available through 1) high energy
  phosphate sources (PCr) 2) Glycolysis 3)
  aerobic oxidation. Potential problems with
  lactate formation A) Availability of adequate
  oxygen in cells B) rate of glycolytic flux and
  H2 production-mismatch with transport into
  mitochondria C) Activity of LDH pyruvate
  accepts H2 and lactate forms

2
Metabolic Machinery

• Accepting pyruvate depends upon Mitochondrial
  reticulum (network). Activity of Krebs Cycle
  Electron transport chain insulates cell from high
  pyruvate. Fiber-type specific LDH drives pyruvate
  to lactate. Fast-twitch fiber disadvantage for
  sedentary subjects.

3

• 3-4

4
Response to Energy charge changes

• Rate of ATP production based on demand- Rising
  ADP and drop in ATP prime modulators.
• Creatine Kinase-high energy phosphate controller
• Phosphofructokinase-glycolytic rate
• Dehydrogenases of Krebs Cycle
• Cytochrome oxidase of ETC controls rate of O2
  acceptor of electrons in ETC.

5
Fuel Sources during Exercise

• Intensity and Duration dependent
• Crossover Concept -role of training status
  dictates how far into intensity spectrum fatty
  acids are predominate fuel source
• Transition from rest to exercise-O2 deficit?
  Impact on short-term moderate to hi intensity
  exercise.
• VO2 drift with prolonged exercise.

6
Fig 3-5 3-8
7
Lactate Threshold

• Intensity dependent, training-specific change in
  metabolic response to exercise
• Implications for ventilation, CO2 and muscle
  blood pH changes
• Ability to exercise at or above LT threatens
  exercise session.

8
3-10
9
Ventilatory response

• Ventilatory threshold, anaerobic threshold, or
  Lactate threshold-
• Evaluate rise in Ve, VCO2, and/or Ve/VCO2 ratio.
• Jump in lactate concentrations in blood

10
Recovery from exercise-EPOC

• Re-establish dynamic equilibrium of body at rest
• Core temperature lactate metabolism
  catecholamines glycogen restoration cardiac
  output,
• Contributes to overall exercise energy
  expenditure.
• Combines with exercise VO2 for total energy
  expenditure- VO2 RER used to estimate kcals/
  liter O2 consumed.

11
Normal Cardiorespiratory Responses to Exercise

12
Myocardial Response

• HR-influenced by SNS PSNS circulating
  hormones
• As HR inc. diastole dec. and systoles stays about
  same.
• SV influenced by Frank-Starling
  mechanism/length-tension relationship of
  myocardial cells (Preload or LVEDV)
• Effect of afterload may hinder ventricular
  performance.
• Exercise inc LVEDV, small change in LVESV so SV
  increases.

13

• 3-12

14

• 3-13

15
Cardiac Output

• Table 3-3 HRSV- big difference is in SV.

16
Peripheral Blood Flow

• MAP-balance of increased Q and greater
  vasodilation Inc. cardiac output of heart raises
  SBP while peripheral vasodilation keeps diastolic
  fairly constant.
• TPR-vessel radius changes-combined efforts of
  vasoconstriction in inactive tissue beds by
  SNS-alpha receptors, and local vasodilatory
  substances (Nitric oxide) and beta receptors of
  SNS.
• Arm vs leg exercise also a factor.

17
Dynamic vs static exercise

• Table 3-2

18
Arms vs legs

• Absolute vs relative workload
• Arms can do less work (65-80 of VO2max of legs,
  HR 10 bpm lower) than legs, so same absolute
  workload is at a higher of arms capacity than
  legs. See greater HR, SBP, DBP, Ve, VO2, lactate
  with lower SV.
• When arms legs exercise at same relative
  workload, CV response quite similar.

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Myocardial Work

• 3-15

20
Factors determining myocardial demand

• 3-16

21
Cardiorespiratory Adaptations to Exercise
Training

• Pulmonary-limited improvements-likely result of
  other adaptations-perhaps at maximal exercise or
  reduced respiratory muscle fatigue in prolonged
  exercise Less lactate in blood may lower
  ventilatory drive greater diffusion capacity
  makes lungs more efficient.
• Central Circulation-major change is greater SV.
  Blood volume expands which stresses ventricle,
  leads to larger ventricular cavity (LVEDV),
  greater ventricular mass improves Preload, which
  leads to greater SV.
• Improved contractility-greater SNS stimulation
  or Ca dynamics in cell.

22

• 22-1

23
Training and Blood Lactate changes

• 22-1

24
Peripheral Circulation

• Decrease in Total peripheral resistancedue to
  increase capillaries improved vasodilator
  effects
• Greater shunting of blood from splancnic
  kidneys to skeletal muscle maintains central
  venous pressure filling of heart

25

• 22-5

26
Specificity Principle

• 22-7

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Muscle Adaptations

• Type of exercise dictates changes
  Endurance-oxidative enzymes-Krebs cycle, oxidases
  of ETC, shutttle of NADH2 fatty acid use
  (carnitine palmitoyal transferase) Glycogen and
  triglyceride storage maintain lower ADP levels
  with more fuel choices
• Fiber type determines magnitude of
  changesmigration toward oxidative