Overview and Basics of Exercise

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					OVERVIEW AND BASICS OF
EXERCISE PHYSIOLOGY


Dianna Purvis MS, ACSM
Department of Military and Emergency Medicine
CHAMP
Topics to Cover

• Background
• Skeletal Muscle Fiber Types
• Energy Systems
• Physiological Responses to Exercise
• Maximal Aerobic Capacity and Exercise
  Testing
• Terms and Concepts Associated with
  Exercise
As a Nation…We Are Getting
Fatter, More Unfit, and at a
Younger Age!
Physical Activity Plays a
Key Role Disease Prevention
The Dose-Response
Relationship for Exercise




                            5
Why Is This Important?

 The importance of cardiorespiratory fitness
  (VO2 max) cannot be overemphasized
    ↓ cardiorespiratory fitness = ↑ morbidity & mortality
     all causes
 NHANES survey 2001/2002
    that 11-30% of adults surveyed had VO2 max values
     in ACSM’s poor category…33.6% adoloscents!
 Despite importance of high aerobic fitness,
  public health surveys show a high level of poor
  aerobic fitness in the US population
How do YOU want YOUR Patients
       to look and feel?
     Before        After
    Stressed     Empowered
    How Much Exercise?

 Daily Aerobic Activity
   10,000 steps per day
   150 – 300 min/week (CDC)
   ACSM guidelines
 Strength exercises 2-3 times
  per week
   Body weight
   Resistance
 Stretch daily
   Consider yoga for flexibility and
    stress management
CDC/ACSM

  http://www.cdc.gov/physicalactivity/everyon
   e/guidelines/adults.html   (CDC)

  http://www.acsm.org (ACSM)


  http://www.aafp.org/online/en/home/clinic
   al/publichealth/aim/foryouroffice.html
   (AIM: Exercise Prescription Tools for
   Clinicians)
The Exercise and Physical
Activity Pyramid




   Adapted with permission of the Metropolitan Life Insurance Company.
Skeletal Muscle
Skeletal Muscle Fiber Types

• Slow-Twitch   •   Characterized by differences in
  Type I            morphology, histochemistry,
                    enzyme activity, surface
                    characteristics, and functional
                    capacity


• Fast-Twitch   •   Distribution shows adaptive
                    potential in response to
  Type IIa          neuronal activity, hormones,
  Type IIx          training/functional demands,
                    and aging
  Characteristics of Human
  Muscle Fiber Types
Other Terminology      Slow Twitch       Fast Twitch
                         Type Ia     Type lla    Type ll(x)
Aerobic Capacity          HIGH       MED          LOW

Myoglobin Content         HIGH       MED          LOW

Color                     RED        PINK        WHITE

Fatigue Resistance        HIGH       MED          LOW

Glycolytic Capacity       LOW        MED          HIGH

Glycogen Content          LOW        MED          HIGH

Triglyceride Content      HIGH       MED          LOW
ATP Is Generated
Through 3 Energy Systems

 1. ATP-PCr system

 2. Glycolytic system

 3. Oxidative system




The process that facilitates muscular contraction
is entirely dependent on body’s ability to provide
& rapidly replenish ATP
   Energy Systems
   for Exercise

                          Mole of    Time to
Energy Systems
                          ATP/min    Fatigue
Immediate: ATP - PCr
                             4      5 to 10 sec
(ATP & phosphocreatine)
Short Term: Glycolytic
                            2.5     1 to 2 min
(Glycogen-Lactic Acid)
                                    Unlimited
Long Term: Oxidative         1
                                      time
1. The ATP–PCr System
ATP-PCr Stores Deplete
Rapidly
2. The Glycolytic System

  Requires 10-12 enzymatic reactions
     to break down glycogen to pyruvate
     or lactic acid, producing ATP
    Occurs in the cytoplasm
    Glycolysis does not require oxygen
     (anaerobic)
    Without oxygen present, pyruvic
     acid produced by glycolysis
     becomes lactic acid
    ATP-PCr and glycolysis provide the
     energy for ~2 min of all-out activity
Conversion of Pyruvic Acid
to Lactic Acid
Energy Sources for the
Early Minutes of Intense
Exercise

 The combined actions of the ATP-PCr and
 glycolytic systems allow muscles to generate
 force in the absence of oxygen; thus these two
 energy systems are the major energy
 contributors during the early minutes of high-
 intensity exercise…
3. The Oxidative System
             The oxidative system uses oxygen to
                generate energy from metabolic
                fuels (aerobic)
               Oxidative production of ATP occurs
                in the mitochondria
               Can yield much more energy (ATP)
                than anaerobic systems
               The oxidative system is slow to turn
                on
               Primary method of energy
                production during endurance events
Common Pathways for the Metabolism
of Fat, Carbohydrate, and Protein
Anaerobic vs. Aerobic
Energy Systems
 • Anaerobic
    ATP-PCr : ≤ 10 – 30 sec
    Glycolysis: < 2 – 3 min


 • Aerobic
    Krebs cycle
    Electron Transport Chain   2 minutes +
INTERACTION OF ENERGY
SYSTEMS
Immediate   Short-term   Long-term
                               Energy Transfer Systems and Exercise
100%
                                           Anaerobic
 % Capacity of Energy System


                                           Glycolysis

                                                                Aerobic
                                                                Energy
                                                                System




                                           ATP - CP



                               10 sec   30 sec       2 min   5+ min
                                          Exercise Time
Aerobic and Anaerobic
ATP Production        Glycolysis

                                  Pyruvate
                                 Limited O2
                  ß-Oxidation
                                             Lactate
                                Acetyl-CoA
                                                       ATP
              FADH2
              NADH+H+
                                Krebs Cycle

               H2O
                +
               ATP
Pulmonary Ventilation

 • Minute ventilation or VE (L/min) = Tidal
   volume (L/breathing) X Breathing rate
   (Breaths/min)
 • Measure of volume of air passing through
   pulmonary system:air expired/minute


         Variables    Tidal Volume   Breathing Rate
                         (L/min)     (breaths/min)

       Rest             10 - 14        10 – 20

       Maximal        100 – 180         40 - 60
       Exercise
Stroke Volume (SV)


 • Amount of blood ejected from heart with
   each beat (ml/beat)


   Rest        Exercise (max)        Max occurs
  80 – 90         110 – 200         40-50% of VO2 max
                (Depending on      untrained
                training status)    Up to 60% VO2 max
                                   in athletes
  Cardiac Output (CO)


• Amount of blood ejected from heart
  each min (L/min)
   CO = SV X HR
   Rest: ~ 5 L/min
   Exercise: ~10 to 25 L/min
• Stroke Volume x Heart Rate
   Fick Equation:
    VO2= CO X (a - v O2)
• Primary Determinant = Heart rate
Heart Rate and VO2max

                             100
   % of Maximal Heart Rate

                             90
                             80
                             70
                             60
                             50
                             40
                             30
                                   0    20   40   60   80   100
                                       % of VO2max
Maximal Oxygen Consumption
(Aerobic Power or VO2 max)
• Greatest amount of O2 a person can use during
  maximal physical exercise
  • Ability to take in, transport and deliver O2 to skeletal muscle
    for use by tissue
  • Expressed as liters (L) /min or ml/kg/min

• Single most useful measurement to characterize the
  functional capacity of the oxygen transport system
 Provides a quantitative measure of capacity for
  aerobic ATP resynthesis
Factors Affecting VO2max

        Intrinsic            Extrinsic
• Genetic            • Training Status
• Gender             • Time of Day
• Body Composition   • Sleep Deprivation
• Muscle mass        • Dietary Intake
• Age                • Nutritional Status
• Pathologies        • Environment
Determinants of VO2max

 Peripheral Factors    Central Factors
• Muscle Blood Flow   • Cardiac Output
• Capillary Density   • Arterial Pressure
• O2 Diffusion        • Hemoglobin
• O2 Extraction       • Ventilation
• Hb-O2 Affinity      • O2 Diffusion
• Muscle Fiber        • Hb-O2 Affinity
  Profiles
Requirements for
VO2max Testing

• Minimal Requirements
     Work must involve large muscle groups
     Rate of work must be measurable and reproducible
     Test conditions should be standardized
     Test should be tolerated by most people
• Desirable Requirements
     Motivation not a factor
     Skill not required
   Common Criteria Used to
   Document VO2 max
• Primary Criteria
   < 2.1 ml/kg/min increase with
    2.5% grade increase often seen
    as a plateau in VO2
• Secondary Criteria
   Blood lactate ≥ 8 mmol/L
   RER ≥ 1.10
   ↑ in HR to 90% of age
    predicted max +/- 10 bpm
   RPE ≥ 17
Aging, Training, and VO2max

                       70                        Athletes
                       60                        Moderately Active
  VO2max (ml/kg/min)




                                                 Sedentary
                       50
                       40
                       30
                       20
                       10
                       0
                            20   30    40 50     60   70
                                      Age (yr)
       Effect of Bed rest on VO2max

                                  0
            % Decline in VO2max
                                                        %Decline in VO2max
                                                    1.4 - 0.85 X Days; r = - 0.73
                             -10

                             -20

                             -30

                             -40
                                      0   10   20    30     40
                                          Days of Bedrest
Data from VA Convertino MSSE 1997
VO2max Classification
for Men (ml/kg/min)
Age (yrs) Low    Fair    Average Good High

 20 - 29   <25 25 - 33   34 - 42   43 - 52 53+

 30 - 39   <23 23 - 30   31 - 38   39 - 48 49+

 40 - 49   <20 20 - 26   27 - 35   36 - 44 45+

 50 - 59   <18 18 - 24   25 - 33   34 - 42 43+

 60 - 69   <16 16 - 22   23 - 30   31 - 40 41+
VO2max Classification for Women
(ml/kg/min)

Age (yrs) Low Fair Average Good High
 20 - 29   <24 24 - 30   31 - 37   38 - 48 49+

 30 - 39   <20 20 - 27   28 - 33   34 - 44 45+

 40 - 49   <17 17 - 23   24 - 30   31 - 41 42+

 50 - 59   <15 15 - 20   21 - 27   28 - 37 38+

 60 - 69   <13 13 - 17   18 - 23   24 - 34 35+
Typical Ways to Measure VO2max


• Treadmill (walking/running)
• Cycle Ergometry
• Arm Ergometry
• Step Tests
Terms and Concepts Associated
with Exercise

• Rating of Perceived Exertion
• Training Heart Rate
• Energy Expenditure
• Thresholds and Exercise Domains
• O2 Deficit and Excess Post-Exercise O2
  Consumption
Approaches to Determining
Training Heart Rate

• Rating of Perceived Exertion
• 60 to 90% of Maximal HR
   Max HR = 180
   60% = 108 and 90% = 162

• 50 to 85% of Heart Rate Reserve
   Max HR = 180 and Resting HR = 70
   HRR = 180 - 70 = 110
   50% = 70 + 65 = 135; 85% = 94 + 70 = 164

• Plot HR vs. O2 Uptake or Exercise Intensity
Rating of Perceived Exertion:
RPE/Borg Scale
6
7    Very, very light
8
9
10   Very light
11
     Fairly light       Lactate Threshold
12
13
     Somewhat hard
14
                        2.0 mM Lactate
15
16   Hard               2.5 mM Lactate
17
     Very hard          4.0 mM Lactate
18
Estimating Maximal
Heart Rate
•   OLD FORMULA: 220 – age

•   NEW FORMULA: 208 - 0.7 X age
       New formula may be more accurate for older persons and is
        independent of gender and habitual physical activity



            Age              Old Formula            New Formula
             60                    160                     166
             40                    180                     180
             20                    200                     194



•   Estimated maximal heart rate may be 5 to 10% (10 to 20
    bpm) > or < actual value.
Energy Expenditure

• MET: Energy cost as a multiple of resting metabolic
  rate
   1 MET = energy cost at rest ~3.5 ml of O2/kg/min
   3 MET = 10.5 ml of O2 /kg/min
   6 MET = 21.0 ml of O2 /kg/min
• 1 L/min of O2 is ~ 5 kcal/L
   VO2 (L/min) ~ 5 kcal/L = kcal/min
• 1 MET = 0.0175 kcal/kg/min
Lactate/Lactic Acid

 • A product of glycolysis formed from reduction of
   pyruvate in recycling of NAD or when insufficient O2 is
   available for pyruvate to enter the Krebs Cycle

 • Extent of lactate formation depends on availability of
   both pyruvate and NAD

 • Blood lactate at rest is about 0.8 to 1.5 mM, but during
   intense exercise can be in excess of 18 mM
   Lactate Threshold

• Intensity of exercise at which blood lactate
  concentration is 1 mM above baseline
  • Production exceeds clearance
• Expressed as a function of VO2max, i.e., 65% of
  VO2max
• Can indicate potential for endurance exercise
  • Lactate formation contributes to fatigue
  • Impairs oxidative enzymes
Lactate Threshold




                1.0 mM above baseline
Pyruvate:Lactate
Blood Lactate as a Function of
Training
 Blood Lactate (mM)




                      25      50     75   100
                      Percent of VO2max
Ventilatory Threshold

 • Point at which pulmonary ventilation increases
   disproportionately with oxygen consumption
   during an increase in workload

 • At this exercise intensity, pulmonary ventilation
   no longer links tightly to oxygen demand at the
   cellular level
Ventilatory Threshold

• During incremental exercise:
   Increased acidosis (H+ concentration)
   Buffered by bicarbonate (HCO3-)

  H+ + HCO3-  H2CO3  H2O + CO2
   Muscle              RBC              Lung

• Marked by increased ventilation
Ventilatory Threshold


• Methods used in research:
   Minute ventilation vs VO2, Work or HR
   V-slope (VO2 & VCO2)
   Ventilatory equivalents (VE/VO2 & VE/VCO2)
• Relation of VT & LT
   highly related (r = .93)
   30 second difference between thresholds
Ventilatory Threshold

              200
                     By Minute Ventilation Method
 VE (L/min)


              150

              100

              50

                0
                    80 100 120 140 160 180
                         Heart Rate
Ventilatory Threshold

     6000      By V Slope Method
     5000

     4000

     3000

     2000
                         VT
     1000
        2000   2500   3000   3500   4000   4500

                  VO 2 (ml/min)
Respiratory Exchange Ratio

 Respiratory exchange ratio (RER or R)
     VCO2 Expired                     Indicates type of substrate being
R=                                    metabolized:
     VO2    Consumed
                                      .7 FAT to 1.0 CHO
 R for fat (palmitic acid)
     VCO2       16 CO2
R=          =            = 0.70     C16H32O2 + 23 O2  16 CO2 + 16 H2O
     VO2        23 O2

 R for carbohydrate (glucose)
     VCO2       6 CO2
R=          =            = 1.00     C6H12O6 + 6 O2  6 CO2 + 6 H2O
     VO2         6 O2
                R can be > 1 during heavy, non-
                steady state exercise due to ↑
                metabolic & respiratory CO2
    Adaptations to Aerobic
    Training
•    Oxidative enzymes
•    Size and number of mitochondria
•    SV and a – VO2 & SV =  VO2 max
•    RHR & HR @ submax exercise
•    Capillary density
•    Blood volume, cardiac output, and O2 diffusion
Exercise Intensity Domains

 • Moderate Exercise
      All work rates below LT
 • Heavy Exercise:
      Lower boundary: Work rate at LT
      Upper boundary: highest work rate at which blood
       lactate can be stabilized (Maximum lactate steady
       state)
 • Severe Exercise:
      Neither O2 or lactate can be stabilized
Lactate and Exercise Domains
Rest-to-Exercise Transitions

 Oxygen uptake increases rapidly
   Reaches steady state within 1-4 minutes
 Oxygen deficit
   Lag in oxygen uptake at the beginning of exercise
   Suggests anaerobic pathways contribute to total
    ATP production
   After steady state is reached, ATP requirement is
    met through aerobic ATP production
Oxygen Deficit and Debt
Recovery From Exercise
Metabolic Responses
 Oxygen debt
   VO2 elevated above rest following exercise to “repay” debt
   Excess post-exercise oxygen consumption (EPOC)
 “Rapid” portion of O2 debt
   Resynthesis of stored ATP & PCr
   Replenishing muscle and blood O2 stores
 “Slow” portion of O2 debt
   Elevated heart rate and breathing =  energy need
   Elevated body temperature =  metabolic rate
   Elevated epinephrine & norepinephrine =  metabolic rate
   Accumulated lactate clearance
EPOC Following Exercise
   Determinants of
   Endurance Performance

                      Endurance



   O2 Delivery            Maximal SS       Other

                        Lactate
      VO2max           Threshold
                                       Economy



Performance measure            Performance measure

				
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posted:3/24/2010
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