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Kin 310 Exercise/Work Physiology

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Kin 310 Exercise/Work Physiology Office hours - HC 2910 F 10:30-11:20 or by appointment (ryand_at_sfu.ca) class email list announcements, questions and responses – PowerPoint PPT presentation

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Title: Kin 310 Exercise/Work Physiology


1
Kin 310 Exercise/Work Physiology
  • Office hours - HC 2910
  • F 1030-1120
  • or by appointment (ryand_at_sfu.ca)
  • class email list
  • announcements, questions and responses
  • inform me of a preferred email account
  • class notes will be posted on the web site in
    power point each week
  • can be printed up to six per page
  • lecture schedule along with reading assignment on
    web site
  • www.sfu.ca/ryand/kin310.htm

2
Overview
  • Discussion of the physiological basis of exercise
    and work
  • Cellular bioenergetics
  • Providing ATP to meet demand
  • Cardiovascular and respiratory compensations and
    capacities
  • Limitations and adaptations to training
  • Molecular level adaptation
  • activity changes the cellular environment -
    stimulating adaptation to better meet demand
  • Fatigue - inability to sustain activity level
  • description of fatigue in the CNS, the
    neuromuscular junction and the muscle cell
  • Ageing - change in physiological capacities -
    impacts of disease and activity level
  • Assessment of work load and physical capacity for
    exercise and work
  • Exercise and the Environment
  • Heat and barometric pressure can create
    additional demands on physiological systems

3
Energy Sources and Recovery from Exercise
  • Ch 2 Foss and Keteyian - Foxs Physiological
    basis for Exercise and Sport- 6th edition
  • all human activity centers around the ability to
    provide energy (ATP) on a continuous basis
  • without energy cellular activity would cease
  • Main sources of energy
  • biomolecules - carbohydrate and fat
  • protein small contribution
  • lecture will review metabolic processes with an
    emphasis on regulation and recovery

4
Energy
  • Energy - capacity or ability to perform work
  • Work - application of a force through a distance
  • Biological work - transport, mechanical and
    chemical work
  • Power - amount work performed over a specific
    time (rate of work)
  • Transformation of energy - forms of energy can
    be converted from one form to another
  • chemical energy in food is transformed into
    mechanical energy of movement or other biological
    work
  • Biological energy cycle

5
ATP - adenosine tri-phosphate
  • Energy harnessed from molecular bonds in
    biomolecules -
  • used to resynthesize ATP - Fig 2.2
  • only energy released from ATP can be utilized for
    cellular work
  • ATP in solution represents immediate source of
    energy available to muscle
  • enzyme (eg. ATPase) break high energy bonds
    between phosphate groups
  • Forming ADP Pi energy
  • Energy used to do biological work
  • Eg Calcium ATPase, myosin ATPase
  • Reaction is reversible (reform ATP)
  • CP -creatine phosphate (phosphocreatine)
  • Enzyme CK - Creatine Kinase
  • Kinases (eg glycolysis)
  • oxidative phosphorylation
  • form NADH, FADH2 then form ATP

6
Sources of ATP
  • Limited quantity of ATP available
  • constant turnover (re-synthesis)
  • - requires energy
  • 3 processes - use coupled reactions
  • ATP-PC system (phosphagen)
  • energy for re-synthesis from CP
  • Anaerobic Glycolysis
  • ATP from partial breakdown of glucose
  • Limited quantities of glucose
  • absence of oxygen
  • generates lactate as end product (pH)
  • Aerobic System
  • requires oxygen
  • oxidation of carbohydrates, fatty acids and
    protein
  • Krebs cycle and Electron Transport

7
Anaerobic sources
  • ATP -PC system (fig 2.4)
  • high energy phosphates
  • energy in CP bond is immediately available
  • as ATP is broken down it is continuously reformed
  • ADP PC(Creatine Kinase) -gt ATP
  • ADP ADP (myokinase) -gt ATP
  • CP reformed during recovery
  • from ATP formed through aerobic pathways
  • Table 2.1 - most rapidly available fuel source -
    very limited quantity
  • Depleted with 10 seconds of maximum activity
  • Recovers quickly

8
Anaerobic Glycolysis
  • Incomplete breakdown of glucose or glycogen to
    lactate
  • 12 separate, sequential chemical reactions
  • breakdown molecular bonds
  • couple reaction to synthesis of ATP
  • yields 2 (glucose) or 3 (glycogen) ATP
  • Rapid but limited production
  • Limited glycogen stores
  • lactate accumulates -gt acidity -gt fatigue -
    unable to sustain demand
  • PFK - phosphofructokinase
  • rate limiting enzyme- slow step in reaction -
    inhibited by acidity
  • Table 2.2

9
Anaerobic Glycolysis
  • Pyruvate is final product of glycolysis
  • pyruvate is converted to lactate when aerobic ATP
    production can not meet demand for ATP
    utilization
  • Inadequate O2 delivery (or high demand)
  • enzyme LDH - lactate dehydrogenase
  • Redox reaction (Fig 2.6)
  • frees up NAD required in glycolysis
  • Allows rapid production of ATP through glycolysis
    - until acidity shuts it down
  • summary fig 2.7
  • glycogen - endogenous fuel
  • within muscle
  • glucose - exogenous fuel
  • comes from blood glucose, released from liver
    glycogen

10
Aerobic Sources of ATP
  • Acetyl groups - 2 carbon units
  • formed from pyruvate and from Beta oxidation of
    free fatty acids
  • NAD and FAD - electron carriers
  • become reduced when biomolecules are oxidized -
    form NADH, FADH2
  • carry these hydrogen atoms to the electron
    transport chain
  • donated and passed down chain of carriers to form
    ATP
  • Oxidative - phosphorylation
  • oxygen is final acceptor of hydrogen, it is
    reduced to H2O
  • occurs in mitochondrial membrane system - cristae

11
Krebs Cycle
  • Fig 2.12 - Krebs Cycle (Citric Acid cycle)
  • Key regulatory enzymes
  • PDH (pyruvate dehydrogenase),CS (citrate
    synthase), SDH (succinate dehydrogenase)
  • NADH - inhibits enzyme activity
  • High NADH - indicates ETC is behind in utilizing
    NADH already produced
  • Availability of ADP also regulates Krebs cycle
    activity
  • ADP and NAD are needed for reactions to occur
  • CO2 produced as molecules are oxidized ( H atoms
    are removed)
  • Krebs Cycle - produces
  • (per acetyl group-2 Carbons)
  • 1 GTP (ATP equivalent)
  • 3 NADH and 1 FADH2

12
ETC
  • Electron Transport Chain (ETC)
  • H atoms passed down series of electron carriers
    by enzymatic reactions coupled to production of
    ATP
  • oxidative phosphorylation
  • each NADH - yields 3 ATP
  • each FADH2 - yields 2 ATP
  • for process to continue, must liberate NAD and
    FAD -
  • Process requires oxygen

13
Aerobic Glycolysis
  • With sufficient oxygen pyruvate moves into
    mitochondria
  • Monocarboxylate transporter
  • law of mass action
  • 1 mole glycogen -
  • glycolysis
  • 2 moles pyruvate 3 moles ATP
  • 2 moles NADH (6 moles ATP after ETC)
  • Krebs - per pyruvate molecule
  • 4 moles NADH (one from PDH)
  • 12 ATP
  • 1 mole FADH2
  • 2 ATP
  • 1 GTP
  • Multiplied by 2 30 moles of ATP
  • 39 ATP per mole of glycogen

14
Fat Metabolism
  • Fat and Protein only oxidized
  • No anaerobic metabolism
  • Fatty acids - 16-18 carbon units
  • acetyl groups (2 carbons) broken off chain to
    enter Krebs cycle one at a time
  • Beta oxidation Fig. 2.15
  • uses 1 ATP for first two carbons only
  • produces 1 NADH and 1 FADH2
  • acetyl co-A through Krebs/ETC
  • Yields 12 ATP
  • total of 16 ATP for first acetyl group
  • 17 for each remaining acetyl group
  • last acetyl group only 12 ATP- as it is not
    produced by beta oxidation
  • 1 mole of palmitic acid-138 moles ATP
  • Key enzymes - B-HAD, and lipases

15
Comparing the Energy Systems
  • Table 2.6
  • energy capacity - amount of ATP able to be
    produced independent of time
  • power - rate of production - time factor
  • aerobic - table represents availability from
    glycogen only - fat is unlimited
  • Rest
  • aerobic - supplies all ATP
  • mainly fats and carbohydrates
  • some lactate 10 mg/dl in blood
  • does not accumulate, but LDH active

16
Exercise
  • Both anaerobic and aerobic
  • relative contribution to ATP production depends
    on
  • intensity and/or duration
  • state of training
  • Dietary factors (replenishment of stores)
  • Energy contribution vs time
  • (Assumes all out activity for time frame )
  • Mcardle, Katch and Katch - Exercise Physiology
  • Immediate - phosphagens - major contributor for
    up to 10 sec
  • Anaerobic Glycolysis - majro contributor for
    30sec - 2.5 min
  • Aerobic metabolism major contributor for 3 min
    onward
  • Contribution of energy systems is a continuum,
    not an on or off situation

17
Experimental evidence
  • Two types of exercise compared in most of the
    following experiments
  • near maximal - short duration
  • sub maximal - longer duration
  • Fig 2.18 glycogen depletion
  • activities below 60 (VO2 max) and above 90 -
    limited glycogen depletion
  • At 75 significant depletion - leading to
    exhaustion (fatigue)
  • 2.18b
  • rate of depletion dependant on demand
  • Volume of depletion related to duration

18
Short duration
  • 2-3 minutes high intensity exercise
  • fig 2.19 - major energy source CH2O
  • ATP and PC will drop rapidly
  • restored in recovery (rapidly)
  • Aerobic contribution limited by its low power
    output
  • also takes 2-3 min to increase output
  • oxygen deficit - period during which level of O2
    consumption is below that necessary to supply all
    ATP required by exercise demands
  • ATP supplied by anaerobic systems to make up for
    aerobic shortfall
  • rapid accumulation of lactate
  • 200 mg/dl in blood / muscle

19
Prolonged Exercise
  • 10 minutes or longer
  • Aerobic fat and carbohydrate metabolism are main
    sources of ATP
  • CHO dominate up to 20 min
  • fats minor but supportive role
  • after 1 hr fats become dominant source of ATP
  • at lower intensities (lt 60 Hr max) fats also
    have greater contribution
  • fig. 2.20
  • fatigue during aerobic exercise is not associated
    with lactate, but other factors - discussed later
    in semester
  • Fig 2-22 activities require blend of anaerobic
    and aerobic systems
  • energy continuum

20
Control and Regulation
  • Matching provision of ATP to demand is needed so
    performer does not experience early or undue
    fatigue
  • Enzymes, hormones, substrates interact to modify
    flow through metabolic pathways of each system
  • Table 2.7
  • Flow through different pathways is often modified
    by activating and inactivating key enzymes
  • Influences over enzymes include
  • high vs low energy state of cell(NAD)
  • Hormone levels (epinephrine, glucagon)
  • amplification of hormone effects
  • competition for ADP (between enzymes)
  • adequacy of oxygen supply
  • power output requirements relative to aerobic
    power (demand)

21
Regulation
  • In general we observe
  • regulation within muscle cell,
  • And influences from outside the cell
  • both serving to modify regulatory enzymes in each
    pathway
  • Fig 2.23
  • Energy State regulation
  • ADP/ATP ratio
  • very quick - tightly linked to rate of energy
    expenditure
  • Hormone Amplification
  • cAMP 2nd messenger systems - amplification
  • Ep and Glucagon - activate phosphorylase -
    glycogen breakdown
  • lipase - fat breakdown

22
Regulation
  • Substrates -
  • eg. NADH - buildup
  • In cytosol stimulates LDH - frees NAD
  • occurs when ETS is maximized
  • can not oxidize NADH fast enough
  • Also inhibitory in Krebs cycle (DHs)
  • eg. Inc Pyruvate
  • stimulates PDH - entry into Krebs
  • PDH also influenced by phosphorylation
  • Fig 6.8 Brooks
  • Oxidative State Regulation
  • O2 and ADP availability
  • O2 stimulates cytochrome oxidase (CO)
  • final step in ETC
  • low O2 - inhibits Cytochrome Oxidase
  • Leads to build up of NADH, FADH2
  • key factor is oxygen availability vs demand for
    ATP utilization

23
Recovery from Exercise
  • Ch. 3
  • process of recovery from exercise involves
    transition from catabolic to anabolic state
  • breakdown of glycogen and fats to replenishment
    of stores
  • breakdown of protein to protein synthesis for
    muscle growth and repair
  • Our discussion of recovery will include
  • oxygen consumption post exercise
  • Replenishment of energy stores
  • Lactate metabolism(energy or glycogen)
  • Replenishment of oxygen stores
  • intensity and activity specific recovery
  • guidelines for recovery

24
Recovery Oxygen
  • Recovery O2 - Net amount of oxygen consumed
    during recovery from exercise
  • excess above rest in Litres of O2
  • Fast and Slow components
  • Based on slope of O2 curve
  • first 2-3 min of recovery - O2 consumption
    declines fast
  • then declines slowly to resting
  • Fig 3.1
  • Fast Component - first 2-3 minutes
  • restore myoglobin and blood oxygen
  • energy cost of elevated ventilation
  • energy cost of elevate heart activity
  • replenishment of phosphagen
  • volume of O2 for fast component area under
    curve
  • related to intensity not duration

25
Recovery Oxygen
  • Slow Component
  • elevated body temperature
  • Q10 effect - inc metabolic activity
  • cost of ventilation and heart activity
  • ion redistribution Na/K pump
  • glycogen re-synthesis
  • effect of catecholamines and thyroid hormone
  • oxidation of lactate serves as fuel for many of
    these processes
  • duration and intensity do not modify slow
    component until threshold of combined duration
    and intensity
  • After 20 min and 80
  • We observe a 5 fold increase in the volume of the
    slow component

26
Energy Stores
  • Both phosphagens (ATP, CP) and glycogen are
    depleted with exercise
  • ATP/CP - recover in fast component
  • measured by sterile biopsy, MRS
  • rate of PC recovery indicative of net oxidative
    ATP synthesis (VO2)
  • study of ATP production
  • 20-25 mmol/L/min glycogen and all fuels
  • during exercise
  • CP can drop to 20, ATP to 70
  • CP lowest at fatigue, rises immediately with
    recovery
  • Fig 3.2 - very rapid recovery of CP
  • 30 sec 70, 3-5 min 100 recovery

27
Phosphagen Recovery(cont.)
  • Fig 3.3
  • occlusion of blood flow - no phosphogen recovery
  • requires aerobic metabolism
  • estimate 1.5 L of oxygen for ATP-PC recovery
  • Energetics of Recovery
  • Fig 3.4
  • breakdown carbs, fats some lactate
  • produce ATP which reforms CP
  • high degree of correlation between phosphagen
    depletion and volume of fast component oxygen
  • Fig. 3.5
  • anaerobic power in athlete related to phosphagen
    potential - Wingate test
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