Bioenergetics:

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Chapter 5

• Bioenergetics
• Fundamentals of Human Energy Transfer

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First Law of Thermodynamics

• Conservation of energy
• Dictates that the body does not produce, consume,
  or use up energy rather, it transforms it from
  one form into another as physiologic systems
  undergo continual change

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The 6 forms of Energy

1. Light (sun)
2. Mechanical
3. Electric
4. Nuclear
5. Heat (solar)
6. Chemical (fuel, oil)

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What is Photosynthesis?

• The process by which plants, use the energy from
  sunlight to produce sugar, which cellular
  respiration converts into ATP, the "fuel" used by
  all living things.
• The conversion of unusable sunlight energy into
  usable chemical energy, is associated with the
  actions of the green pigment chlorophyll.
• Most of the time, the photosynthetic process uses
  water and releases the oxygen that we absolutely
  must have to stay alive.

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• What is the equation for the chemical reaction of
  photosynthesis?
• CO2 H2O ? Glucose O2
• 6CO2 6H2O ? C6 H12O6 6O2

What do muscles use for energy?

• Glucose (sugar) O2 Insulin for work
• Muscle ? muscle cells (trillions) made up of
  nucleus, cytoplasm, mitochondria, organelles,
  etc.

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Exercise Physiology muscles act on the bones to
transform chemical energy (ATP) into mechanical
energy and motion.
Photosynthesis creates sugar, cellular
respiration breaks down sugar
Organisms transform the chemical energy into a
form it can use.
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Redox Reactions

• Chemical reactions that transfer electrons from
  one substance to another are called
  oxidation-reduction reactions

• Redox reactions for short

• The loss of electrons during a redox reaction is
  called oxidation

• The acceptance of electrons during a redox
  reaction is called reduction

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Oxidation
Glucose loses electrons (and hydrogens)
Glucose
Oxygen
Carbon dioxide
Water
Reduction
Oxygen gains electrons (and hydrogens)
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Key Point

• The limits of exercise intensity ultimately
  depend on the rate that cells, extract, conserve,
  and transfer chemical energy in the food
  nutrients to the contractile filaments of
  skeletal muscle

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Bioenergetics

• Bioenergetics is the subject of a field of
  biochemistry that concerns energy flow through
  living systems.
• It is the study of the metabolic processes that
  can lead to the production and utilization of
  energy in forms such as ATP molecules.
• How we break down energy nutrients into usable
  energy (ATP)

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Bioenergetics

• Potential energy
• Energy associated with a substances structure or
  position.
• Kinetic energy
• Energy of motion.
• Potential energy and kinetic energy
• The total energy of any system
• Releasing potential energy (in the bonds of
  macronutrients) transforms it into kinetic energy
  of motion.

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Some of the ways we transfer energy through
bioenergetics

• Anabolic build up
• requires ATP
• Catabolic break down
• yields ATP

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CHAPTER 6

• Energy Transfer in the Body

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3 ways a muscle cell can produce ATP

• ATP/PCr system
• Anaerobic glycolysis (cytoplasm of muscle cell)
• Lactate shuttle
• Without enough oxygen, muscle cells break down
  glucose to produce lactic acid
• Lactic acid is associated with the burn
  associated with heavy exercise
• If too much lactic acid builds up, your muscles
  give out
• Aerobic glycolysis (mitochondria of muscle cell)
• Glycolysis
• The Krebs cycle
• Electron transport

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Some Definitions

• Glucose simple sugar. The energy required of
  muscles to do work.
• Glycolysis the degradation of glucose.
• Aerobic glycolysis
• Anaerobic glycolysis
• Glycogenolysis the process of carbohydrate
  degradation when the starting substrate is stored
  glycogen.
• Lipolysis the degradation of fats (lipids)
• All ysis reactions require the work of enzymes
  to catalyze (speed up) their reactions.

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Glycolysis occurs in the cytoplasm (the water
medium of a cell)
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HIGH-ENERGY PHOSPHATES

• Adenosine Triphosphate the energy currency
• Powers all of cells energy requiring processes
• Potential energy extracted from food
• Energy is stored in bonds of ATP
• Body stores 80-100g of ATP at any one time
• If its there it gets used quickly (1-3 seconds
  of explosive all-out exercise)
• Energy is transformed to do work

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HARNESSING ATPs POTENTIAL ENERGY

• ADP forms when ATP joins with water (hydrolysis)
• Outermost phosphate is released
• Catalyzed by the enzyme ATPase
• Limited currency
• Low ATP levels in cells create sensitivity to
  ATP/ADP

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At the onset of exercise, ATP is split into ADP
Pi to provide energy for muscular contraction.
The increase in ADP stimulates creatine kinase to
breakdown PCr to resynthesize ATP.
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PHOSPHOCREATINE THE ENERGY RESEVOIR

• Anaerobic resynthesis of ATP
• ADP PCr ? ATP Cr
• Hydrolyzed by the enzyme creatine kinase
• ADP is phosphorylated to ATP
• Creatine may be phosphorylated back to PCr
• Cells store 4-6 times more PCr than ATP
• Gee, why is there so much hype over creatine
  supplements?

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IMPORTANT BY-PRODUCTS

• If ATP is constantly being broken down we must be
  talking about continuous movement (i.e.,
  exercise), therefore hydrolysis and
  phosphorylation stimulate
• Glycogenolysis
• Glycolysis
• Respiratory pathways of mitochondria
• If glycolysis moves into mitochondria, we must be
  talking about aerobic glycolysis!
• Anaerobic glycolysis occurs in the cytoplasm only.

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The Krebs Cycle

• animation

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ENERGY RELEASE FROM FOOD

• Carbohydrate
• Glycolysis
• Occurs in cytosol
• Series of chemical reactions
• The breakdown of Glucose to pyruvate to acetyl
  CoA
• If pyruvate is broken down into acetyl CoA we are
  talking about aerobic glycolysis (aerobic
  respiration) where???
• If pyruvate is not broken down into acetyl CoA it
  is reformulated into lactate meaning we are
  talking about which type of glycolysis (aerobic
  or anaerobic?)
• Limited quantities of ATP are generated
• Glucose is cleaved into 2-pyruvate molecules
• See page 187 in text

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In the Cytoplasm of the Cell
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In the Mitochondria of the Cell
Aerobic Glycolysis
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Aerobic Glycolysis
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Aerobic Glycolysis
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Aerobic respiration is divided into two
processes the Krebs cycle, and the Electron
Transport Chain, which produces ATP through
chemiosmotic phosphorylation. The energy
conversion is as follows C6H12O6 6O2 -gt
6CO2 6H2O energy (ATP) muscular work
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LACTATE FORMATION

• Pyruvate may be reduced to form lactate
• Occurs in an anaerobic state
• Lactate dehydrogenase drives this reversible
  reaction
• Oxidation of glucose, which causes protons to be
  released into solution
• pH drops as proton concentration rises
• What does a lowered pH mean?
• Reduction of pyruvate to lactate helps to buffer
  the solution

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LACTATE IS NOT A WASTE PRODUCT

• Blood lactate potential uses
• Lactate shuttle
• Converted to pyruvate and oxidized as an energy
  source in another cell
• Gluconeogenesis
• Converted back to glucose in the liver in Cori
  Cycle

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GLYCOGENESIS

• Metabolism of glucose to glycogen
• Is this an anabolic or catabolic reaction?
• Regulation of glycogen metabolism
• Glycogen Synthase drives the reaction

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GLYCOGENOLYSIS

• Metabolism of glycogen to glucose
• In the liver
• Glycogen Phosphorylase drives the reaction
• Glucose released into blood
• Maintains blood glucose levels
• Epinephrine stimulates Glycogen Phosphorylase

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ENERGY RELEASE FROM FOOD

• Citric Acid Cycle
• Also known as Krebs Cycle
• Continues oxidation of
• Carbohydrates following glycolysis
• Fatty acids following beta oxidation
• Some amino acids following deamination
• Whats the purpose of the krebs cycle?
• See page 189

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The Krebs Cycle

• animation

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TOTAL ENERGY TRANSFER FROM GLUCOSE CATABOLISM
Ok, decent
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ENERGY RELEASE FROM FAT

• Adipocytes
• Site of fat storage and mobilization
• Fat is stored primarily as triglycerides
• Mobilization
• First step in utilizing fatty acids is Lipolysis
• Triglycerides are split into fatty acids and
  glycerol
• Hormone Sensitive Lipase drives lipolysis

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FATTY ACIDS FROM LIPOPROTEINS

• Lipoproteins also transport triglycerides
• What are the 2 common lipoproteins?
• Lipoprotein Lipase (LPL) catalyzes hydrolysis of
  these triglycerides
• LPL is located on surface of surrounding
  capillaries

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OXIDATION OF FAT

• Beta Oxidation
• Cleaves two-carbon compounds from fatty Acetyl
  CoA molecule
• Two-carbon acetyl groups enter Citric Acid Cycle
• Oxidation produces NADH (an enzyme)

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WOW!
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FATE OF GLYCEROL

• Conversion to Pyruvate via glycolytic action
• Gluconeogenesis
• Converted to Glucose in Liver

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HORMONAL EFFECTS

• Lipolysis is stimulated by
• Epinephrine
• Norepinephrine
• Glucagon
• Growth Hormone
• When would these hormones rise/decrease during
  the day?

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TOTAL ENERGY TRANSFER FROM FAT CATABOLISM
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PROTEIN AS A FUEL SOURCE

• Deamination
• Nitrogen removal from amino acid
• Occurs in liver and muscles
• Enter Citric Acid Cycle for oxidation
• Transamination
• Amine group transferred

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PROTEIN AS A FUEL SOURCE

• Glucogenic ?
• May be used to form
• Pyruvate must now be used in creating ATP
• Oxaloacetate
• Malate
• Ketogenic ?
• May be used to form
• Acetyl-CoA possibly form Ketone bodies
• Acetoacetate
• High protein diets??

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LIPOGENESIS

• Glucose conversion to fat
• Fatty acids are synthesized
• Protein conversion to fat
• Excess amino acids deaminated
• Converted to acetyl CoA
• Fatty acids are synthesized

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Lets Review

• The citric acid cycle is the third step in
  carbohydrate catabolism (the breakdown of
  sugars). Glycolysis breaks glucose (a
  six-carbon-molecule) down into pyruvate (a
  three-carbon molecule). In eukaryotes, pyruvate
  moves into the mitochondria. It is converted into
  acetyl-CoA and enters the citric acid cycle.
• In protein catabolism, proteins are broken down
  by proteases into their constituent amino acids.
  The carbon backbone of these amino acids can
  become a source of energy by being converted to
  Acetyl-CoA and entering into the citric acid
  cycle.
• In fat catabolism, triglycerides are hydrolyzed
  to break them into fatty acids and glycerol. In
  the liver the glycerol can be converted into
  glucose by way of gluconeogenesis. In many
  tissues, especially heart tissue, fatty acids are
  broken down through a process known as beta
  oxidation which results in acetyl-CoA which can
  be used in the citric acid cycle.
• The citric acid cycle is always followed by
  oxidative phosphorylation. This process extracts
  the energy (as electrons) from NADH and QH2,
  oxidizing them to NAD and Q, respectively, so
  that the cycle can continue. Whereas the citric
  acid cycle does not use oxygen, oxidative
  phosphorylation does.
• The total energy gained from the complete
  breakdown of one molecule of glucose by
  glycolysis, the citric acid cycle and oxidative
  phosphorylation equals about 36 ATP molecules.
  The citric acid cycle is called an amphibolic
  pathway because it participates in both
  catabolism and anabolism.

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FATS BURN IN A CARBOHYDRATE FLAME!!!

• Glycolytic production of pyruvate required to
  maintain activity of beta oxidation
• Production of pyruvate is quicker by glycolysis
  than with beta oxidation
• However, beta oxidation yields much more energy
• If there is one thing you learn in this course,
  please remember this phrase. It is the basis
  behind all fad diets and gimic weight loss
  programs.

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SLOWER RATE OF ENERGY RELEASE FROM FAT

• Rate of fat oxidation is slower than that for
  carbohydrate
• Carbohydrate oxidation helps maintain fat
  oxidation rates
• Carbohydrate depletion impairs exercise
  performance

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Wheres the application in all of this?

• When you exercise and you get in better shape
  you increase the amount of mitochondria in a
  muscle cell thus increasing the capacity to
  create ATP and sustain endurance and/or intensity
  by becoming a better breather (aerobic) and
  utilizing fat as a substrate.whew!

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End of review whew!

• Lets take a break!
• Begin chapter 7 next slide
• Put your seat belt on

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Chapter 7 ENERGY SPECTRUM OF EXERCISE

• Each energy systems relative contribution to
  maximal exercise duration
• ATP/ PCr
• Anaerobic
• Glycolysis
• Anaerobic
• Aerobic
• Citric Acid Cycle and ETS
• Aerobic
• Energy allocations progress on a continuum

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Methods of Measuring Heat Production

• Indirect Calorimetry
• Open-circuit spirometry
• Approximately 4.82 kcal (5) release when a blend
  of CHO, lipid, and protein burns in 1 Liter of
  oxygen
• Indirect calorimetry through oxygen uptake
  measurement provides the basis for quantifying
  the caloric cost of most physical activities.
• Portable spirometer
• Spirometer is small and is carried in a pack
• Air volume is measured
• Sample is collected to measure concentrations of
  gases
• How do textbooks and charts know that if a 150
  lb. woman plays tennis for 1 hour shell burn 350
  calories, or a 175lb. man weightlifting burns 100
  calories per hour.

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Methods of Measuring Heat Production

• Indirect Calorimetry
• Bag Technique
• Air is collected in a large bag (Douglas Bag)
• Small sample is measured for gas concentrations

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Methods of Measuring Heat Production

• Computerized Instrumentation
• Air flow is measured for volume
• Gas analyzers measure concentrations of oxygen
  and carbon dioxide

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Caloric Transformation of Oxygen

• The complete oxidation of a molecules carbon and
  hydrogen atoms to CO2 and water end-products
  requires different amounts of O2 due to inherent
  chemical differences in carbohydrate, lipid, and
  protein composition.

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How is the complete oxidation of a nutrient
measured in terms of activity?

• Respiratory Quotient (RQ)
• Approximates the nutrient mixture catabolized for
  energy during rest and aerobic exercise.
• Represents gas exchange from substrate metabolism
  on the cellular level (steady-state)
• RQ CO2 produced O2 consumed
• See page 728

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STEADY STATE

• Energy demand energy supply
• Oxygen consumption energy needs of task
• Submaximal constant load exercise (work does not
  change)

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Respiratory Exchange Ratio (RER)

• Reflects what is happening on a total body level.
• Calculated during non-steady state exercise
• Calculation of RER is the same as RQ
• Metabolic calculations
• Calculating energy expenditure during exercise
• Volume of air
• Concentrations of O2 and CO2

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RER and RQ

• RER-Respiratory Exchange Ratio
• Ventilatory measurement
• Reflects gas exchange between lungs and pulmonary
  blood
• Exceeds 1.0 during heavy exercise due to
  buffering of lactic acid which produces CO2

• RQ-Respiratory Quotient
• Cellular Respiration and substrate utilization
• 0.7 Fat
• 1.0 Carbohydrate
• 0.8 Protein
• Equivalent to RER only under resting or
  steady-state conditions
• Can never exceed 1.0
• RQ is used to estimate energy expenditure,
  however, when RQ is not available, assume
• 5 kcal ?L-1

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SUBSTRATE UTILIZATION DURING EXERCISE

• Percent contribution of fat and carbohydrate
  utilization
• Fat 70 (70 more O2 to CO2 molecules
  consumed)
• CHO 100 (equal of CO2 to O2 molecules
  consumed)
• Valid only for steady-rate exercise
• No change in work

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Turn to page 241

• VO2 Max 1.5 l/min in steady state condition for
  30 min
• RER .87
• Caloric equivalent for an R of .87 4.887 kcals/l
  VO2
• Total energy expenditure for task 220 kcals
• 57 from oxidation of CHO 125 kcals
• 42 from oxidation of fat 92 kcals

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• Steady state VO2 Max .90 l/min for 30 min
• RER .75
• Energy expenditure for task 128 kcals
• Energy from oxidation of CHO 15.6 20 kcals
• Energy from oxidation of fat 84.4 108 kcals
• Do these make sense according to the non-pro RQ?

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Maximal Oxygen Consumption

• Maximal volume of oxygen one can consume
• VO2 max
• Maximal oxygen uptake
• Maximal aerobic power
• Aerobic capacity
• Provides a quantitative measure of capacity for
  aerobic ATP resynthesis

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Max VO2 of male and female Olympic caliber
athletes in different sport categories compared
to healthy sedentary subjects.

• See Figure 7.12 on page 244
• Normative data for VO2 Max

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Factors Affecting VO2 Max

• Exercise Mode variations in VO2 max during
  different modes of exercise reflect the quantity
  of muscle mass activated.
• Heredity current estimates of the genetic
  effect ascribe about 20 to 30 for VO2 max, 50
  for maximum heart rate, and 70 for physical
  working capacity.
• Training State aerobic capacity with training
  improves between 6 and 20, although increases
  have been reported as high as 50 above
  pretraining levels.
• Gender VO2 max for women typically average
  15-30 below scores for men. The male generates
  more total aerobic energy simply because he
  possesses a relatively large muscle mass and less
  fat than the female.
• Body Composition differences in body mass
  explain roughly 70 of the differences in VO2max
  among individuals.
• Age beyond age 25, VO2 max declines steadily at
  abou 1 per year, so that by age 55, it averages
  27 below values reported for 20 year olds.

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Tests of Aerobic power

• Graded exercise test (GXT)
• Continuous effort, but usually consists of
  increments in exercise intensity.
• See exercise mode pg. 248
• Treadmill test - see page 248
• Running test page 254
• WARNING! These are only estimates of aerobic
  power.

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VO2 max Measurement

• Treadmill walking or running
• Cycle ergometer
• Bench stepping
• Flume swimming
• Simulated rowing
• Arm-crank exercise

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Treadmill Protocols

• Bruce walk/run
• Balke walk only
• Naughton walk only
• Astrand run only
• Ellestad walk/run
• Harbor protocol depends on subjects fitness
  level

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Lactate Threshold

• Lactate accumulation above baseline
• Usually begins at approximately 55 of VO2 max
• Factors that contribute to rise in Lactic Acid
  concentration
• Hypoxia low oxygen levels (hyperventilating)
• Anaerobic Glycolysis (enhanced by presence of epi
  and norepi)
• Decreased removal of lactate
• Increased recruitment of Fast-twitch fibers

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MUSCLE FIBER TYPES

• Slow twitch Type I red, lots of mitochondria
• Highest aerobic capacity
• Lowest glycolytic capabilities - high capacity to
  generate ATP by oxidative metabolic processes
• Found in postural muscles and neck
• Fast twitch Type II
• Type IIa red, lots of mitochondria
• Medium glycolytic and aerobic capabilities
• Type IIb white, few mitochondria
• Highest glycolytic capacity - Faster contracting
  fibers have greater ability to split ATP
• Lowest aerobic capacity
• Found in arms and legs

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