Energy Systems for Exercise

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Energy Systems for Exercise
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Energy Sources

• From Food
• CHO 4 kcal
• Fat 9 kcal
• Protein 4 kcal
• For Exercise
• ATP ? ADP P energy (for muscle contraction)

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Adenosine Triphosphate

• Energy-carrying molecule found in the cells of
  all living things.
• ATP captures chemical energy obtained from the
  breakdown of food molecules and releases it to
  fuel other cellular processes.
• Cells require chemical energy for three general
  types of tasks to drive metabolic reactions that
  would not occur automatically to transport
  needed substances across membranes and to do
  mechanical work, such as moving muscles.

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Methods of Supplying ATP For Energy

• Stored ATP PC (Creatine Phosphate) or ATP-PC
• Anaerobic metabolism/ glycolysis/lactic acid
  system
• Aerobic metabolism

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ATP-PC System

• Short duration (lt10 secs) anaerobic
• Uses stored ATP
• Strength/power movements
• Replenishes rapidly

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The ATP-PC system

• Active at the beginning of all forms of
  activities
• Especially important in high intensity exercises
  like weight lifting that require short bursts of
  energy.
• The source of fuel for the ATP-PC system is ATP
  and PC that is stored in the muscles. Only a
  small quantity can be stored, so this energy
  source is only effective for activities that last
  ten seconds or less.

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Glycolysis

• Breakdown of carbohydrates for fuel
• Fuel stored in the muscle as glycogen / delivered
  to the muscle as blood glucose
• Glycolysis can produce fuel for 30 seconds to a
  minute for moderate heavy resistance training

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Fast (Anaerobic) Glycolysis(The lactic acid
system)

• Fast glycolysis is used when oxygen is in short
  supply.
• Fast glycolysis results in the formation of
  lactic acid
• An increase in lactic acid in the muscle can
  involve muscular fatigue and ultimately cessation
  of exercise.

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Active Recovery from Exercise (Cool down)

• Facilitates lactate removal because of
• increased perfusion of blood through the liver
  and heart
• increased blood flow in muscles because muscle
  tissue oxidizes lactate

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Slow (Aerobic) glycolysis(The aerobic system)

• Slow glycolysis is used if there is enough oxygen
  to allow a continuous supply of fuel.
• The byproduct of this form of glycolysis is
  pyruvate, which is not converted to lactic acid
  but is transported elsewhere.
• Pyruvate is eventually dissipated as sweat/urine

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Aerobic/Oxidative System

• Supplies energy to the muscle through the use of
  continuous oxygen transport.
• System works at rest and during very low
  intensity exercise such as walking
• This form of energy primarily utilizes fats (70)
  and carbohydrates (30) as fuel sources, but as
  intensity is increased there is a switch in
  substrate majority from fats to carbohydrates

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Oxygen Uptake During Aerobic Exercise

• Increases sharply at onset
• Levels off within a few minutes if pace is
  constant (steady state)
• Oxygen demand met by supply

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Maximal Oxygen Uptake (VO2 max)

• The region where oxygen uptake plateaus and does
  not increase despite an additional increase in
  exercise intensity.

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Oxygen Deficit

• Difference between oxygen consumed during
  exercise and amount that would have been consumed
  had a steady rate, aerobic metabolism occurred at
  onset of exercise.

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Order of energy production

• Initial energy comes form ATP stored in muscles
  about 2 seconds
• Then the ATP-PC system about 10 seconds
• Then the Lactic acid system about 1 minute
• Then the Aerobic system 1minute onwards

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The Energy-Time Continuum

• As the work time increases, the percentage of
  energy contributed by the aerobic system
  increases.

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Blood Lactate Threshold

• Exercise intensity at the point of lactate
  buildup.
• Predicts aerobic exercise performance.
• Untrained 55 of VO2 max.
• Trained 75 of VO2 max.