Bioenergetics

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C H A P T E R
Bioenergetics of Exercise and Training
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Objectives

• Discuss the role of ATP
• Explain the three energy systems
• Discuss training effects on bioenergetics
• Recognize substrates
• Design programs to stimulate growth

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Energy

• The ability or capacity to perform work
• Bioenergetics is the flow of energy in a
  biological system
• Digestion of fats, CHO, protein
• Synthesis of fats, glycogen, protein
• Release of energy stored in fat, CHO, protein

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Metabolism

• Sum of all anabolic and catabolic processes in
  the body
• Series of enzyme controlled chemical reactions to
  build up and break down substances in the body
• Anabolic- to build up (store energy)
• Catabolic- to break down (release energy)

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Control of Metabolism

• Protein based enzymes control the rate of
  metabolism
• Substrate is the substance that an enzyme works
  on
• Enzymes work by a lock and key mechanism
• Enzymes are not changed in the reaction

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Chemical Structures of ATP, ADP, and AMP with
phosphates.
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Energy stored in the chemical bonds of adenosine
triphosphate (ATP) is used to power muscular
activity. The replenishment of ATP in human
skeletal muscle is accomplished by three basic
energy systems phosphagen, glycolytic, and
oxidative.
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1. Phosphagen (Anaerobic) System
?Occurs in the absence of molecular oxygen
?Provides ATP for short-term, high-intensity
activities
?Is active in the start of all exercise
regardless of intensity
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Substrate Depletion and Repletion

• Substrate- starting materials for bioenergetic
  reactions
• Fatigue
• Depletion of phosphagens
• Depletion of glycogen
• Depletion of fatty acids
• Depletion of amino acids
• Depletion of lactate

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Glycogen

• Glycogen supply is limited 300-400 grams in
  muscle, and 70-100 grams in liver
• Both aerobic and anaerobic exercise increase
  glycogen stores, repletion is related to
  post-exercise CHO ingestion
• The rate of glycogen depletion is related to the
  intensity of exercise high intensity
  intermittent exercise can cause glycogen depletion

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Restore CHO Stores
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2. Glycolytic System
?Breaks down carbohydrates to produce ATP that
supplements the supply from the phosphagen system
for high-intensity muscular activity
?May go in one of two ways fast glycolysis or
slow glycolysis 41 ATP production difference
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• During fast glycolysis, pyruvate is converted to
  lactic acid, providing ATP at a fast rate.
• With slow glycolysis, pyruvate is transported to
  the mitochondria for use in the oxidative system.
• ATP-PC 4 moles ATP/min (capacity 1 mole)
• FG-2 moles ATP/min (capacity 1.5 moles)
• Aerobic-1 mole ATP/min (capacity 90 moles)

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Fast glycolysis has commonly been called
anaerobic glycolysis. Slow glycolysis has been
called aerobic glycolysis. Also a function of
fiber type.
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Glycolysis
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Lactate Threshold (LT) and Onset of Blood
Lactate Accumulation (OBLA)
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3. Oxidative (Aerobic) System
?Requires molecular oxygen
?Provides ATP at rest and during low-intensity
activities
?Uses primarily carbohydrates and fats as
substrates
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The oxidative metabolism of blood glucose and
muscle glycogen begins with glycolysis. If oxygen
is present in sufficient quantities the end
product of glycolysis, pyruvate, is not converted
to lactic acid but is transported to the
mitochondria, where it is taken up and enters the
Krebs Cycle.
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Krebs Cycle
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In general, an inverse relationship exists
between the relative rate and total amount of ATP
that a given energy system can produce. 1. The
phosphagen energy system primarily supplies ATP
for high-intensity activities of short
duration 2. The glycolytic system for moderate-
to high-intensity activities of short to medium
duration. 3. The oxidative system for
low-intensity activities of long duration.
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Table 5.3 Effect of Event Duration on Primary
Energy System Used
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The extent to which each of the three energy
systems contributes to ATP production depends
primarily on the intensity of muscular activity
and secondarily on the duration. At no time,
during either exercise or rest, does any single
energy system provide the complete supply of
energy.
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Energy Systems During Exercise
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The use of appropriate exercise intensities and
rest intervals allows for the selection of
specific energy systems during training and
results in more efficient and productive regimens
for specific athletic events with various
metabolic demands.
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Implications for
Training and Conditioning

1. Nutritional implications
2. Metabolic specificity
3. Interval training
4. Combined training

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Nutrition

• Carbohydrate intake
• During activity
• Following activity
• Maximize glycogen storage

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Metabolic Specificity

• Training must be metabolically specific to an
  activity to elicit maximal performance
  enhancement
• Metabolic profiling
• Recovery is aerobic
• High intensity anaerobic activities train aerobic
  metabolism

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Interval Training

• More work can be performed with less fatigue by
  exercising at high intensities with intermittent
  rest
• Metabolic profile of interval training similar to
  performance in a variety of sports
• 90-100 ATP-PC 5-10 secs 112, 120
• 75-90 FG 15-30 secs 13, 15
• 30-75 FG, Ox 1-3 min 13, 14
• 20-35 Ox gt 3 min 11, 13

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Combination Training

• Aerobic training may reduce anaerobic performance
• Decrease strength
• Decrease muscle mass
• Resistance training has a generally positive
  effect on aerobic performance
• Extensive aerobic training to enhance recovery
  from anaerobic exercise is not necessary and may
  be counterproductive

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Next Class

• Chapter 18 anaerobic part 1