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Exercise Physiology. J.M. Cairo, Ph.D. LSU Health Sciences Center New Orleans, Louisiana [email protected]. Somatic Factors Sex and Age Body Dimension Health. Training Adaptation. Psychic Factors Attitude Motivation. Bioenergetics Storage Fuels Fuel Intake Oxygen Uptake - PowerPoint PPT Presentation
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Exercise Physiology
J.M. Cairo, Ph.D.
LSU Health Sciences Center
New Orleans, Louisiana
Bioenergetics Storage Fuels Fuel Intake
Oxygen Uptake Cardiac Output
• Heart Rate• Stroke Volume
(A-V)O2 Difference• Pulmonary Ventilation
Nature of WorkIntensityDurationRhythm
TechniquePosition
Somatic FactorsSex and Age
Body DimensionHealth
Psychic FactorsAttitude
Motivation
Training Adaptation
EnvironmentTemperature
AltitudeInhaled Gases
Energy Yielding Processes
Physical Performance CapacityFrom Astrand and Rodahl,
Textbook of Work Physiology, New York
McGraw-Hill, 1972
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.
Oxygen Consumption versus Workload
0
500
1000
1500
2000
2500
3000
10 20 30 40 50 60 70 80 90 100
Percent of Maximum Workload
Oxy
gen
Com
sum
ptio
n (m
L/m
in)
VO2 = 250 ml/minQ = 5 L/minCaO2 = 200 ml/L of whole bloodCvO2 = 150 ml/L of whole bloodCaO2-CvO2 = 50 ml/L of whole blood
RESTING CONDITIONS FOR A TYPICAL HEALTHY ADULT
VO2 = 5000 ml/minQ = 25 L/minCaO2 = 200 ml/L of whole bloodCvO2 = 20 ml/L of whole bloodCaO2-CvO2 = 180 ml/L of whole blood
MAXIMUM EXERCISE RESPONSE FOR A
WORLD CLASS ATHLETE
Heart Rate Response to Increasing Work
0
20
40
60
80
100
120
140
160
180
200
10 20 30 40 50 60 70 80 90 100
Percent of Maximium Oxygen Consumption
Hea
rt R
ate
Maximum Heart Rate and Age
100
120
140
160
180
200
220
20 30 40 50 60 70
Age (years)
Ma
xim
um
Hea
rt R
ate
HRMAX = 220 - age (yrs)
Stroke Volume vs Workload
0
20
40
60
80
100
120
140
160
10 20 30 40 50 60 70 80 90 100
Percent Maximum Oxygen Consumption
Str
oke
Vol
ume
(mL
/bea
t)
PRELOAD
Volume of blood in the ventricle at the end of diastoleLVEDV
Venous ToneSkeletal Muscle
PumpThoraco-abdominal
Pump
Venous Return
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
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
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
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
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+
Bioenergetics Storage Fuels Fuel Intake
Oxygen Uptake Cardiac Output
• Heart Rate• Stroke Volume
(A-V)O2 Difference• Pulmonary Ventilation
Nature of WorkIntensityDurationRhythm
TechniquePosition
Somatic FactorsSex and Age
Body DimensionHealth
Psychic FactorsAttitude
Motivation
Training Adaptation
EnvironmentTemperature
AltitudeInhaled Gases
Energy Yielding Processes
Physical Performance Capacity
VO2 = 5000 ml/minQ = 25 L/minCaO2 = 200 ml/L of whole bloodCvO2 = 20 ml/L of whole bloodCaO2-CvO2 = 180 ml/L of whole blood
MAXIMUM EXERCISE RESPONSE FOR A
WORLD CLASS ATHLETE
VO2 = 2500 ml/minQ = 15 L/minCaO2 = 200 ml/L of whole bloodCvO2 = 33 ml/L of whole bloodCaO2-CvO2 = 167 ml/L whole blood
MAXIMUM EXERCISE RESULTS FOR A TYPICAL
HEALTHY ADULT
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.
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
Effects of Endurance Training on Skeletal Muscle Morphology
• Capillary Density
• Myoglobin
• Mitochondria
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
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
Effects of Chronic Physical Activity on Aerobic Function
Submaximal Values Effect
Oxygen Consumption Unchanged-Decreased
Cardiac Output Unchanged
Heart Rate Decreased
Stroke Volume Increased
Systolic Blood Pressure Decreased
Rate-Pressure Product Decreased
Minute Ventilation Decreased
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
Exercise Testing Strategies
• Incremental versus steady state tests
• Modes of exercise– Treadmills
• Bruce versus Balke Protocol
– Cycles• Ramp Protocol
Noninvasive Measurements
• Respiratory– Vt
– Fb
– VE
– FIO2
– FEO2
– FECO2
– Pulse oximetry
– PtcO2, PtcCO2
Noninvasive Measurements
• Cardiovascular– Heart rate– Arterial blood pressure– Electrocardiogram
• Modified chest leads
• 12 lead ECG
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
Reasons for Stopping a Test
• ECG criteria– Severe ST segment depression (>3 mm)
– ST segment elevation (>1 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
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)
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
Derived Variables• Cardiovascular
– Heart rate reserve• HR reserve = HRmax (predicted) – HRmax (achieved)
– O2 pulse• O2 pulse = VO2/HR = SV X (CaO2-CvO2)
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 (>20 mmHg)– Rise in blood pressure (>300 mmHg, diastolic
> 130 mmHg)– Ataxia
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
– θAT 1.4L
*Patient stopped exercise due to dyspnea
Case #20000512
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
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– θAT 1.30L
* Patient stopped exercise due to angina and presence of multiple PVBs
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
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
– θAT 1.10L
* Patient stopped exercise due to extreme dyspnea
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
– θAT 0.95L
* Patient stopped exercise due to extreme dyspnea
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
– θAT 1.10L
* Patient stopped exercise due to extreme dyspnea
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
Basal Metabolic Rate
Metabolism Associated with Muscular Activity
Hormonal Effects on Metabolism
Insulation
Blood Flow
Radiation Conduction Evaporation
Heat Production Heat Loss
REGULATION OF BODY TEMPERATURE
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
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
How Fast Is Heat Transferred From Deep Tissues to Skin
• Insulation Systems– Skin and subcutaneous tissue (i.e., fat)
• Blood Flow– Cutaneous circulation
How Fast Is Heat Loss From the Skin to the Surrounding
Environment
• Radiation
• Conduction
• Evaporation
Definitions• Radiation
– Loss of heat by infrared heat rays (5-20m 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)
“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
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 10°C 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
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
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
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