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Exercise Physiology

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How do cells convert carbohydrates, fats and proteins into ATP ... Carbohydrates and fats provide nearly all the energy during exercise ... – PowerPoint PPT presentation

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Title: Exercise Physiology


1
Exercise Physiology
Krishna Asundi, PhD Research Fellow Harvard
School of Public Health
2
Course Schedule
  • March 3rd Bioenergetics and Exercise Metabolism
  • Submit list of references (cite the sources
    appropriately APA writing style)
  • March 10th Physiology of Training
  • Submit abstract of paper
  • March 31st Training for Performance
  • April 7th Oral Presentations
  • April 21st Oral Presentations
  • May 9th Term paper deadline

3
Scientific Term Paper
  • Abstract (5 points)
  • Summarizes the central question principal
    findings and conclusions.
  • Should spark the readers interest to continue
    reading the paper
  • Primary research question (5 points)
  • A focused question on a scientific topic
  • Scientific Review (15 points)
  • Comprehensive review of the literature focused on
    the topic
  • Discussion/ Interpretation (25 points)
  • What is known and what is uncertain?
  • What conclusions can be drawn from the studies
    found in the literature
  • What are the uncertainties/ confounding factors
  • Writing (5 points)
  • Clarity of exposition/ style
  • Structure
  • Annotation (5 points)
  • Reference list
  • Appropriate use, style and consistency of
    citations

4
Presentation
  • Short 10 15 minutes (No more than 15 slides!)
  • Focus on the most interesting study/studies from
    your term paper, dont try to cover everything
    you are writing about
  • Provide enough background for people to
    understand the question
  • Structure
  • Research Question
  • Background
  • Question asked by Study of interest
  • Results from the study of interest
  • How do the results contribute to answering your
    question
  • Remaining questions
  • Conclusions

5
Review
  • Muscles convert ATP energy into mechanical energy
  • Muscle length and contraction speed affects force
    production
  • Muscles contain fast and slow twitch fibers with
    different biochemical and contractile properties
  • Fast fibers anaerobic energy system, fatigue
    quicker and produce more force
  • Slow fibers aerobic energy system, resist
    fatigue, contract slower

6
Review
  • The circulatory system transports gases (O2, CO2)
    and nutrients throughout the body
  • Heart beat, stroke volume, and vasodilatation /
    vasoconstriction act to regulate blood flow
  • Gas exchange between the blood and atmosphere
    occurs in the lungs
  • Ventilation acts to regulate the rate of exchange

7
Todays Class
  • How do cells convert carbohydrates, fats and
    proteins into ATP
  • Aerobic vs. Anaerobic Respiration
  • Maximal Oxygen Uptake (VO2 max)
  • Metabolic Response to Exercise
  • Fuel Selection during exercise

8
Bioenergetics
9
Bioenergetics
  • Describes how energy is transformed in cells
  • Molecules contain energy in the bonds that hold
    them together
  • Reactions that form strong bonds (absorb energy)
    are called endergonic
  • Reactions that break strong bonds (release
    energy) are called exergonic

10
Fuels for the body
11
Carbohydrates
  • Yield approximately 4 kcal per gram
  • Monosaccharide (glucose, fructose)
  • Disaccharides (sucrose),
  • Polysaccharides (starch, cellulose)
  • Are stored in the body as glucose or glycogen
    (long chains of glucose)
  • Breakdown of glycogen into glucose occurs in
    muscle cells and the liver
  • Glucose and glycogen, stored in muscle cells and
    the liver, are depleted within a few hours during
    exercise

12
Fats
  • Yield approximately 9 kcal of energy per gram
  • Fatty acids
  • Triglycerides (three fatty acids and one glycerol
    molecule)
  • Phospholipids, Steroids
  • Fatty acids are used by cells for energy
  • Fatty acids are stored in the body as
    triglycerides
  • Triglycerides are primarily stored in fat cells,
    but also found in skeletal muscle
  • Phospholipids and steroids are not used as energy
    sources

13
Proteins
  • Yield approximately 4 kcal of energy per gram
  • Are a chain of several amino acids
  • Proteins must be broken down into amino acids to
    be used to produce energy

14
Adenine Triphosphate
  • ATP High energy phosphate compound
  • Serves as the bodys universal energy donor
  • Energy from food is converted into ATP which is
    then used for various cellular processes
  • Three metabolic pathways to produce ATP

15
Energy Systems
16
ATP PC system
  • Pathway by which phosphocreatine is used to
    generate ATP
  • Simplest and fastest method of producing ATP
  • Very short term, high intensity exercise
  • 50m sprint, powerlift, high jump etc.
  • Muscle cells only store small amounts of PC
  • PC reformation requires ATP and only occurs
    during recovery from exercise

17
Glycolysis
  • Breakdown of glucose into pyruvic acid or lactic
    acid
  • Short term (less than 10 minutes), bursts of
    energy
  • Basketball, football, volleyball
  • 1 glucose molecule produces 2 molecules of
    pyruvate and 2 or 3 molecules of ATP
  • If oxygen is available, pyruvic acid is used in
    oxidative phosphorylation
  • If oxygen is not available, pyruvic acid is
    converted to lactic acid

18
Oxidative Phosphorylation
  • Pathway by which energy in fatty acids, amino
    acids and pyruvate (from glycolysis) is used to
    generate ATP
  • Occurs inside the mitochondria
  • Three Steps
  • 1) Substrates (fatty acids, amino acids,
    pyruvate) are converted to Acetyl-CoA
  • 2) Krebs Cycle Acetyl-CoA is converted into
    several intermediaries. In this process electrons
    are shuttled to the Electron Transport Chain
  • 3) Electron transport chain Electrons are
    transported through the membrane of the
    mitochondria. Electron movement creates a flow
    of H. Energy from this flow of H is used to
    generate ATP.
  • O2 is required to accept the electrons from the
    last step of the transport chain

19
ATP Production
  • ATP PC System
  • 1 PC molecule generates 1 ATP molecule
  • Glycolysis
  • 1 glucose molecule produces 2 3 ATP molecules
  • Oxidative Phosphorylation
  • 1 glucose molecule produces 32 33 ATP molecules

20
Energy System Selection
  • High intensity
  • 2 20 seconds, ATP production dominated by
    ATP-PC system
  • 20 45 seconds, dominated by glycolysis
  • gt 45 seconds, a combination of the ATP PC,
    glycolysis and aerobic systems
  • Lower intensity
  • 10 minutes, 80 aerobic
  • gt30 minutes, nearly all aerobic
  • Recovery
  • The aerobic energy system restores energy when
    intensity decreases

21
Energy System Selections
  • During exercise a combination of systems are used
    to produce energy
  • The rate of energy demand (power output) dictates
    how energy will be produced

From Powers Howley. (2007). Exercise
Physiology. McGraw-Hill.
22
Exercise Metabolism
23
Exercise Metabolism
  • Describes the relationship between fuel
    use/selection, energy pathways and by-products
  • The majority of the bodys energy needs are
    provided aerobically
  • Anaerobic pathways typically supplement based on
    energy demands

24
Aerobic Energy
  • During low intensity exercise, the majority of
    energy is provided aerobically
  • Also, energy spent anaerobically is recovered
    aerobically (i.e. after a sprint)
  • Energy produced aerobically requires O2
  • Therefore, O2 uptake can be used as a measure for
    energy use

25
Oxygen Uptake (VO2)
  • With incremental increases in work output, oxygen
    uptake increases linearly to a maximum
  • VO2 max Maximal capacity of the body to
    transport and utilize oxygen during exercise

26
VO2 Max
  • The respiratory and cardiovascular systems and
    muscle composition all affect a persons VO2 max
  • A high VO2 max indicates a higher power output
    over an extended period of time
  • It also indicates faster energy recovery
  • Good for marathon runners, unimportant for power
    lifters
  • What about football players?

27
Fuel Selection
  • Carbohydrates and fats provide nearly all the
    energy during exercise
  • Proteins contribute less than 2 to energy
    production during exercise
  • Selection of carbohydrates or fats is determined
    by exercise intensity and duration

28
Fuel Selection
From Powers Howley. (2007). Exercise
Physiology. McGraw-Hill.
  • As intensity increases carbohydrate use
    increases, fat use decreases
  • As duration increase, fat use increases, carb use
    decreases

29
Optimal Fat Metabolism
  • Two factors contribute to the rate of fat
    metabolism
  • Rate of energy expenditure
  • of energy that comes from fat
  • This results in an optimal VO2 max for burning fat

From Powers Howley. (2007). Exercise
Physiology. McGraw-Hill.
30
Fuel Sources
31
Carbohydrates
  • More than 80 are stored as glycogen in muscles
  • About 15 are stored in the liver and released as
    glucose into the blood stream when needed
  • About 5 are found in the blood and extracellular
    fluid as glucose

32
Fats
  • The majority (gt96) of fat is stored as
    triglycerides in fat cells
  • Triglycerides are also stored in muscle

33
Effects of Exercise Intensity
  • Plasma FFA (fat from fat cells) is the primary
    fuel source for low intensity exercise
  • As intensity increases, the source shifts to
    muscle glycogen

From Powers Howley. (2007). Exercise
Physiology. McGraw-Hill.
34
Effects of Exercise Duration
From Powers Howley. (2007). Exercise
Physiology. McGraw-Hill.
  • As exercise continues, energy source switches
    from a mix to primarily plasma FFA and blood
    glucose

35
Review
  • ATP is generated by three bioenergetic pathways
  • ATP-PC
  • Glycolysis
  • Oxidative phosphorylation
  • Pathway selection for energy depends on exercise
    intensity and duration
  • Energy are primarily obtained from carbohydrates,
    fats or protein
  • Steady state oxygen uptake can be used as a
    measure of work intensity (VO2)
  • Fuel selection and fuel source are affected by
    exercise intensity and duration

36
Next Week
  • Physiology of Training
  • Effects of training on VO2 max
  • Effects of training on performance and
    homeostasis
  • Physiological effects of strength training
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