Exercise Physiology

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Exercise Physiology

• J.M. Cairo, Ph.D.
• LSU Health Sciences Center
• New Orleans, Louisiana
• jcairo_at_lsuhsc.edu

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Somatic Factors Sex and Age Body Dimension Health
Psychic Factors Attitude Motivation
Training Adaptation

• Bioenergetics
• Storage Fuels
• Fuel Intake
• Oxygen Uptake
• Cardiac Output
• Heart Rate
• Stroke Volume
• (A-V)O2 Difference
• Pulmonary Ventilation

Environment Temperature Altitude Inhaled Gases
Nature of Work Intensity Duration Rhythm Technique
Position
Energy Yielding Processes
From Astrand and Rodahl, Textbook of Work
Physiology, New York McGraw-Hill, 1972
Physical Performance Capacity
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From Richardson, DR, Randall, DC, Speck, DF
Cardiopulmonary System. Madison, CT, Fence
Creek, 1998
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From Wasserman, K., Hansen, J.E., Sue, D.Y.,
Casaburi, R, and Whipp, B.J. Principles of
Exercise Testing and Interpretation, 3rd Edition.
Philadelphia, Lippincott Williams and Wilkins,
1999.
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The Fick Principle

• VO2 Q x (CaO2 - CvO2)

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RESTING CONDITIONS FOR A TYPICAL HEALTHY ADULT
VO2 250 ml/min Q 5
L/min CaO2 200 ml/L of whole
blood CvO2 150 ml/L of whole
blood CaO2-CvO2 50 ml/L of whole blood
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MAXIMUM EXERCISE RESPONSE FOR A WORLD CLASS
ATHLETE
VO2 5000 ml/min Q 25
L/min CaO2 200 ml/L of whole
blood CvO2 20 ml/L of whole blood CaO2-CvO2
180 ml/L of whole blood
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Cardiac Output


Heart Rate
Stroke Volume


Preload
Contractility
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Afterload
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HRMAX 220 - age (yrs)
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PRELOAD
Volume of blood in the ventricle at the end of
diastole LVEDV
Venous Return
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Frank-Starling Mechanism
Stroke Volume
LVEDV
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PRELOAD
Volume of blood in the ventricle at the end of
diastole LVEDV
Venous Return
Skeletal Muscle Pump
Venous Tone
Thoraco-abdominal Pump
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Contractility
Stroke Volume
LVEDV
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Factors influencing the Pulmonary Response to
Exercise

• Ventilation
• Diffusion of Oxygen and Carbon Dioxide Across the
  Alveolar-Capillary Membrane
• Perfusion
• Ventilation/Perfusion
• O2 and CO2 Transport
• O2 uptake by the tissues

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Control of Breathing During Exercise

• Immediate Response
• Neural Component
• Central Command
• Learned Response
• Direct Connection from Motor Cortex
• Coordination in Hypothalamus
• Proprioceptors or Mechanoreceptors

From Levitzky, MG Pulmonary Physiology, 5th
Edition. New York, McGraw-Hill, 1999
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Control of Breathing During Exercise

• Response to Moderate Exercise
• Arterial Chemoreceptors
• Metaboreceptors
• Nociceptors
• Cardiac Receptors
• Venous Chemoreceptors
• Temperature Receptors

• Response to Severe Exercise
• Arterial Chemoreceptors
• Central Chemoreceptors

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Factors Influencing the Maintenance of the
Arterial Oxygen Content (CaO2)

• Increase in Alveolar Ventilation
• Decrease in VD/VT
• Increased Perfusion of the Lungs
• Decrease in Pulmonary Vascular Resistance
• Recruitment and Distension of Pulmonary
  Capillaries
• Improvement in VA/QC
• Increased Diffusion of O2 and CO2 across the
  Alveolar-Capillary Membrane

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Effective Ventilation VD/VT
0.40
VD/VT
0.25
Rest
Max
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Factors Influencing Unloading/Uptake of Oxygen at
the Tissues (?CvO2)

• Shifting of the Oxyhemoglobin Dissociation Curve
  to the Right
• Increase in Core Temperature
• Increase in CO2 Production
• Increase in H

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Somatic Factors Sex and Age Body Dimension Health
Psychic Factors Attitude Motivation
Training Adaptation

• Bioenergetics
• Storage Fuels
• Fuel Intake
• Oxygen Uptake
• Cardiac Output
• Heart Rate
• Stroke Volume
• (A-V)O2 Difference
• Pulmonary Ventilation

Environment Temperature Altitude Inhaled Gases
Nature of Work Intensity Duration Rhythm Technique
Position
Energy Yielding Processes
Physical Performance Capacity
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MAXIMUM EXERCISE RESPONSE FOR A WORLD CLASS
ATHLETE
VO2 5000 ml/min Q 25
L/min CaO2 200 ml/L of whole
blood CvO2 20 ml/L of whole blood CaO2-CvO2
180 ml/L of whole blood
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MAXIMUM EXERCISE RESULTS FOR A TYPICAL HEALTHY
ADULT
VO2 2500 ml/min Q 15 L/min CaO2 200
ml/L of whole blood CvO2 33 ml/L of whole
blood CaO2-CvO2 167 ml/L whole blood
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Principles of Physical Training

• Overload
• Specificity
• Reversibility

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Training for Improved Aerobic Endurance

• Type of Exercise
• Intensity
• Duration
• Frequency

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Anaerobic Threshold

• The anaerobic threshold is defined as the level
  of exercise VO2 above which aerobic energy is
  supplemented by anaerobic mechanisms and is
  reflected by an increase in lactate and
  lactate/pyruvate ratio in skeletal muscle and
  arterial blood.
• See Wasserman, K., Hansen, J.E., Sue, D.Y.,
  Casaburi, R, and Whipp, B.J. Principles of
  ExerciseTesting and Interpretation, 3rd Edition.
  Philadelphia, Lippincott Williams and Wilkins,
  1999.

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Karvonen Formula for Prescribing Exercise Heart
Rate

• HREx HRRest 0.60 (HRMax HRRest)

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Detraining and VO2 MAX

• Decreased maximum attainable cardiac output and
  arteriovenous O2 difference
• Initial (12-14 days)
• Decrease due to decreased stroke volume
• Decreased plasma volume
• Prolonged (3 weeks 12 weeks)
• Attenuation of arteriovenous O2 difference
  changes
• Decreased muscle mitochondrial density

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Effects of Endurance Training on Skeletal Muscle
Morphology

• Capillary Density
• Myoglobin
• Mitochondria

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Effects of Endurance Training on Skeletal Muscle
Metabolism

• Mobilization of FFA
• Transport of FFA from Cytoplasm to the
  Mitochondria
• Mitochondrial Oxidation of FFA
• Beta-oxidation
• Lactate Removal

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Effect of Conditioning on Heart Rate Response
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Effects of Chronic Physical Activity on Aerobic
Function
Resting Values Effect
Oxygen Consumption Unchanged
Heart Rate Decreased
Systolic Blood Pressure Unchanged-Decreased
Diastolic Blood Pressure Unchanged-Decreased
Rate-Pressure Product Decreased
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Effects of Chronic Physical Activity on Aerobic
Function
Submaximal Values Effect Effect
Oxygen Consumption Oxygen Consumption Unchanged-Decreased
Cardiac Output Cardiac Output Unchanged
Heart Rate Heart Rate Decreased
Stroke Volume Stroke Volume Increased
Systolic Blood Pressure Systolic Blood Pressure Decreased
Rate-Pressure Product Rate-Pressure Product Decreased
Minute Ventilation Minute Ventilation Decreased
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Effects of Chronic Physical Activity on Aerobic
Function
Maximal Values Effect
Oxygen Consumption Increased
Cardiac Output Increased
Heart Rate Unchanged-Decreased
Stroke Volume Increased
Arteriovenous O2 Difference Increased
Systolic Blood Pressure Unchanged
Rate-Pressure Product Unchanged
Ejection Fraction Increased
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Exercise Testing Strategies

• Incremental versus steady state tests
• Modes of exercise
• Treadmills
• Bruce versus Balke Protocol
• Cycles
• Ramp Protocol

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Noninvasive Measurements

• Respiratory
• Vt
• Fb
• VE
• FIO2
• FEO2
• FECO2
• Pulse oximetry
• PtcO2, PtcCO2

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Noninvasive Measurements

• Cardiovascular
• Heart rate
• Arterial blood pressure
• Electrocardiogram
• Modified chest leads
• 12 lead ECG

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Normal ECG Changes During Exercise

• P wave increases in height
• R wave decreases in height
• J point becomes depressed
• ST segment becomes sharply up sloping
• QT interval shortens
• T wave decreases in height

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Reasons for Stopping a Test

• ECG criteria
• Severe ST segment depression (gt3 mm)
• ST segment elevation (gt1 mm in non-Q wave lead)
• Frequent ventricular extrasystole
• Onset of ventricular tachycardia
• New atrial fibrillation or supraventricular
  tachycardia
• Development of new bundle branch block (if the
  test is primarily to detect underlying coronary
  disease)
• New second or third degree heart block

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Invasive Measurements

• Arterial blood gases
• pHa, PaCO2, PaO2
• Blood lactate levels
• Pulmonary artery catheterization
• Pulmonary vascular pressures (PA, PAWP)
• Mixed venous blood gases (pHv, PvCO2, PvO2)

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Derived Variables

• Peak VO2 versus VO2Max
• Respiratory
• VD/VT
• VD/VT PaCO2- PECO2/PaCO2
• P(A-a)O2
• P(a-et)CO2
• Breathing reserve
• Breathing reserve MVV VE max

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Derived Variables

• Cardiovascular
• Heart rate reserve
• HR reserve HRmax (predicted) HRmax (achieved)
• O2 pulse
• O2 pulse VO2/HR SV X (CaO2-CvO2)

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Reasons for Stopping a Test

• Symptoms and signs
• Patient requests stopping because of severe
  fatigue
• Severe chest pain, dyspnea, or dizziness
• Fall in systolic blood pressure (gt20 mmHg)
• Rise in blood pressure (gt300 mmHg, diastolic gt
  130 mmHg)
• Ataxia

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Case 20020240

• Resting Data
• Age 75 yrs
• Sex Male
• VC 3.5L (100)
• IC 2.3L (102)
• TLC 6.0L (110)
• FEV1 3.90L (95)
• FEV1/VC 80
• MVV 100L
• Hct 44

• Exercise Data
• VO2 (Peak) 1.75L (100)
• HRMAX 140 bpm
• SBP 155/84 180/75
• VEMAX 70L/min
• VD/VT 0.35 0.25
• P(A-a)O2 20 torr
• ?AT 1.4L

Patient stopped exercise due to dyspnea
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Case 20000512

• Exercise Data
• VO2 (Peak) 1.55L(58)
• HRMAX 168 bpm
• SBP 150/92 205/120
• VEMAX 48L
• VD/VT 0.40 0.30
• P(A-a)O2 20 torr
• ?AT 1.30L

• Resting Data
• Age 48 yrs
• Sex Male
• VC 4.75L (93)
• IC 3.94L (95)
• TLC 5.90L (98)
• FEV1 3.90L (93)
• FEV1/VC 80
• MVV 90L

Patient stopped exercise due to angina and
presence of multiple PVBs
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Findings Suggesting High Probability of Coronary
Artery Disease

• ST segment depression 2 mm
• Downsloping ST segment depression
• Early positive response within 6 minutes
• Persistence of ST depression for more than 6
  minutes into recovery
• ST segment depression in 5 or more leads
• Exertional hypotension

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Case 20011120

• Resting Data
• Age 60 yrs
• Sex Male
• VC 3.75L (80)
• IC 2.75L (70)
• TLC 6.53L (130)
• FEV1 2.80L (65)
• FEV1/VC 60
• MVV 65L

• Exercise Data
• VO2 (Peak) 1.75L (68)
• HRMAX 128 bpm
• SBP 135/88 200/110
• VEMAX 60L/min
• VD/VT 0.40 0.38
• P(A-a)O2 45 torr
• ?AT 1.10L

Patient stopped exercise due to extreme dyspnea
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Case 20011452

• Resting Data
• Age 70 yrs
• Sex Male
• VC 3.65L (78)
• IC 2.28L (72)
• TLC 6.03L (81)
• FEV1 2.20L (6)
• FEV1/VC 60
• MVV 95L
• DLCO 10.8 (35)

• Exercise Data
• VO2 (Peak) 1.32L (65)
• HRMAX 152 bpm
• SBP 175/86 227/90
• VEMAX 90L/min
• VD/VT 0.45 0.48
• P(A-a)O2 45/68 torr
• PaO2 64/52 torr
• ?AT 0.95L

Patient stopped exercise due to extreme dyspnea
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Case 2001367

• Resting Data
• Age 60 yrs
• Sex Male
• VC 1.75L (40)
• IC 1.55L (42)
• TLC 8.03L (120)
• FEV1 0.54L (15)
• FEV1/VC 30
• MVV 35L
• DLCO 19 (59)

• Exercise Data
• VO2 (Peak) 1.75L (68)
• HRMAX 128 bpm
• SBP 135/88 200/110
• VEMAX 60L/min
• VD/VT 0.40 0.38
• P(A-a)O2 45 torr
• ?AT 1.10L

Patient stopped exercise due to extreme dyspnea
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Temperature Regulation
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Definitions

• Core Temperature
• Measured as oral, aural, or rectal temperature
• Temperature of deep tissues of the body
• Remains relatively constant (?1ºF or ?0.6ºC)
  unless a person develops a febrile condition
• Nude person can maintain core temperature even
  when exposed to temperatures as low as 55ºF or as
  high as 130ºF in dry air
• Skin Temperature
• Rises and falls with the temperature of the
  surroundings

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REGULATION OF BODY TEMPERATURE
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Heat Production

• Laws of Thermodynamics
• Heat is a by-product of metabolism
• Basal metabolic rate of all cells of the body
• Effect of muscular activity on metabolic rate
• Effect of endocrinology on metabolic rate (i.e.,
  thyroxin, growth hormone, testosterone)
• Effect of autonomic nervous system on metabolic
  rate

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Heat Loss

• How fast is heat transferred from deep tissues to
  the skin
• How rapidly is heat transferred from the skin to
  the surrounding environment

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How Fast Is Heat Transferred From Deep Tissues to
Skin

• Insulation Systems
• Skin and subcutaneous tissue (i.e., fat)
• Blood Flow
• Cutaneous circulation

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How Fast Is Heat Loss From the Skin to the
Surrounding Environment

• Radiation
• Conduction
• Evaporation

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Definitions

• Radiation
• Loss of heat by infrared heat rays (5-20?m or
  10-20X wavelength of visible light)
• Conduction
• Loss of heat from the body to a solid object
• Evaporation
• Loss of heat from the body through water vapor to
  the surrounding atmosphere
• Convection
• Effects of changes in the external environment
  (e.g., wind and water)

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Wind Chill Factor

• Effect of wind on skin temperature temperature
  of calm air that would produce equivalent cooling
  of exposed skin
• Cooling effect of air convection equals the
  square root of the wind velocity
• For example, air temperature feels twice as cold
  at a wind velocity of 4 mph than if the wind
  velocity is 1 mph

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ºF 35.74 0.6215T - 35.75V(100.16)
0.4275V(100.16)
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Regulation of Body Temperature Role of the
Hypothalamus

• Anterior Hypothalamus Preoptic Area
• Heat-sensitive neurons
• Demonstrate a 10-fold increase in firing rate
  when there is a 10C increase in body temperature
  resulting in profuse sweating and cutaneous
  vasodilation
• Cold-sensitive neurons
• Increase in firing rate to a decrease in body
  temperature resulting in cutaneous
  vasoconstriction and inhibition of sweat
  production

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Temperature RegulationSkin and Deep Tissue
Receptors

• Although the skin contains both cold and warmth
  sensory receptors, there are far more cold
  receptors than warmth receptors (10 times more
  cold than warmth)
• Stimulation of these cold receptors will result
  in shivering, inhibition of sweating, and
  promotion of cutaneous vasoconstriction

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Temperature RegulationSkin and Deep Tissue
Receptors

• Deep tissue receptors are found in spinal cord,
  in the abdominal viscera, and in the great veins
  in the upper abdomen and thorax
• Although these receptors are exposed to core body
  temperature rather than skin temperature, they
  function like the skin receptors in that they are
  concerned with preventing hypothermia

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Hormonal Control of Temperature

• Chemical Thermogenesis
• Ability of norepinephrine and epinephrine to
  uncouple oxidative phosphorylation
• Brown fat
• Thyrotropin-releasing hormone ?
  Thyroid-stimulating hormone ? Thyroxine
• Stimulated by cooling of the anterior
  hypothalamic-preoptic area
• Requires several weeks of exposure to cold to
  cause hypertrophy of the thyroid gland

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Abnormalities of Body Temperature Regulation

• Fever
• Effect of pyrogens
• Brain lesions
• Heatstroke
• Frostbite
• Malignant Hyperthermia