Exercise and Biochemistry

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Exerciseand Biochemistry
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Energy Partitioning

• Onset of maximal exercise
• Demand for energy is high
• There is a lag time in reaching max. aerobic
  energy production
• Intensity of exercise
• Nature of onset of exercise
• Low intensity exercise, long duration
• Heart rates around 160 beats/min
• Energy provided largely by aerobic pathways
• Produce ATP at sufficient rates
• Greatest fuel economy

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Energy Partitioning

• High intensity exercise of short duration
• Energy provided by anaerobic pathways
• Offers high rates of ATP
• Low fuel economy
• At any point in time
• Muscle fibers will be functioning aerobically and
  anaerobically
• Anaerobic pathway reliance increases as speeds
  increase
• Speeds greater than 8-10 m/s or 20 mph
• Back-up of substrates in mitochondria
• Not due to oxygen depletion

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Energy Partitioning

• Main drive to recruit the anaerobic pathway
• Aerobic energy pathways are working at max, but
  demand for ATP is still rising.
• The use of anaerobic pathways result in
• Increase in blood lactate levels
• Anaerobic threshold
• Energy Partitioning
• Contribution of each energy pathway to the total
  energy requirement for exercise.

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Energy Partitioning

• Measurement of pathway utilization
• Estimated by measuring O2 uptake and CO2 and
  lactate production at various speeds
• Sprinters (2 furlongs or 400 m)
• Obtain approx. 60 of energy from anaerobic
• 40 aerobically
• Traveling abt 40 mph
• Middle distance runners (1 ½ miles, Derby)
• Approx. 80 aerobically
• And 20 anaerobically
• Start and finish of the race
• Endurance (100 miles at 10 mph)
• Approx. 96 aerobically
• And 4 anaerobically

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Energy Partitioning

• Anaerobic energy production
• Normally begins around 150-180 beats/min
• Equivalent of a good or ¾ speed canter
• Initial appearance of lactic acid
• Factors affecting onset of anaerobic E production
• Unfit compared to a Fit horse
• High proportion of fast twitch high glycolyti
  muscle fibers
• Health problems
• Upper airway obstruction
• Cardiovascular disease
• Lower airway disease
• Pain, excitement, and type of warm-up exercise
• Time of feeding
• Environmental conditions

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Energy Partitioning

• How can you tell what fuels are being used for
  energy generation?
• Respiratory exchange ratio (RER)
• Ratio of carbon dioxide production (Vco2,
  liters/m) to oxygen consumption (Vo2, liters/m)
• CHO RER is 1
• Fat RER is 0.7
• RER gt 1 indicates that some of the energy is
  coming from anaerobic lactate acid prod.

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Energy Partitioning

• RER can be used to determine response to
• Dietary manipulation
• RER 0.9 rest
• RER 0.9 typical hay/conc diet
• RER 0.75 high fat diet
• Exercise and training
• May reflect muscle fiber type composition

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Energy Partitioning

• Size of the fuel stores
• How much fuel can a 500kg horse carry?
• Sum of fat, muscle and liver 230kg (500 lbs.)
• Muscle 200 kg (440 lbs)
• Liver 6.5 kg 14.3 lbs)
• Fat 25 kg (55 lbs)
• 95 of glycogen stores are in muscle
• 5 in liver
• 95 of the bodys fat is stored in adipose tissue
• 5 stored w/in the muscles

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Energy Partitioning

• Approx. 10 times as much energy is stored as fat
  compared w/ glycogen.
• Fat is ideal for exercise where the body
  requires
• Slow release of energy
• Large energy reserve
• Training at low speeds and long durations
• Increases the number of enzymes involved in
  oxidative phosphorylation

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Energy Partitioning

• Galloping a fat horse
• Risk breakdown of musculoskeletal structures
• Make it sweat and lose body mass
• Use up muscle glycogen
• Give it an appetite
• Fat is less dense than muscle
• Muscle is 20 more dense
• Dieting and exercise shape change

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Energy Partitioning

• Running out of energy
• Fatigue during exercise
• Never the result of depletion of fat
• Commonly due to depletion of muscular/liver
  glycogen
• Light headed/tired depletion of blood Glu and
  liver glycogen
• Muscle fatigue depletion of muscle glycogen
• Glycogen loading is not recommended

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Energy Partitioning

• Workout schedules
• Maximal sprint or interval work more than 2 to 3
  times a week or consecutive days
• Will not allow glycogen stores to be replenished
  by next bout
• Glycogen breakdown
• Dependent on its concentration
• Breakdown is high w/ high concentrations

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Exercise and Biochemistry

• Homeostasis
• Is the maintenance of a dynamic equilibrium in
  the body.
• Dynamic implies activity, energy, and work.
• Equilibrium refers to balance.
• The whole body is responsible for homeostasis.

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Exercise and Biochemistry

• Steady-state
• Internal environment is unchanging while under
  some stressor (exercise).
• How is this done?
• Control Systems of the body
• Cellular control
• Regulation of protein synthesis, degradation,
  energy production, maintenance of nutrient levels
• Systemic control
• Pulmonary
• Gas exchange
• Cardiovascular
• Gas and nutrient transport

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Exercise and Biochemistry

• Nature of the Control Systems
• Biological control system
• Receptor
• Integrating center
• Effector
• Stimulus or signal
• Negative feedback

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Exercise and Biochemistry

• Example
• Regulation of body CO2
• Increased CO2 triggers receptor
• Sends information to integrating center
  (Respiratory control center) to increase
  breathing.
• Effectors are respiratory muscles.
• Such changes will lower extracellular CO2 back to
  normal conditions thereby re-establishing
  homeostasis.

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Exercise and Biochemistry

• Exercise
• A Test of Homeostatic Control
• Increased lactic acid and acidity
• Challenges acid-balance
• Increased O2 uptake and CO2 production
• Increases in ventilation
• Increases blood flow to working muscles