Transcript Handout - LSU Health Sciences Center New Orleans

Exercise Physiology
J.M. Cairo, Ph.D.
LSU Health Sciences Center
New Orleans, Louisiana
[email protected]
Somatic Factors
Sex and Age
Body Dimension
Health
Nature of Work
Intensity
Duration
Rhythm
Technique
Position
Training
Adaptation




Psychic Factors
Attitude
Motivation
Bioenergetics
Storage Fuels
Fuel Intake
Oxygen Uptake
Cardiac Output
• Heart Rate
• Stroke Volume
(A-V)O2 Difference
• Pulmonary Ventilation
Energy Yielding Processes
From Astrand and Rodahl,
Textbook of Work
Physiology, New York
McGraw-Hill, 1972
Physical Performance Capacity
Environment
Temperature
Altitude
Inhaled Gases
From Richardson, DR,
Randall, DC, Speck, DF:
Cardiopulmonary System.
Madison, CT, Fence Creek,
1998
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.
The Fick Principle
VO2 = Q x (CaO2 - CvO2)
Oxygen Consumption versus
Workload
Oxygen Comsumption
(mL/min)
3000
2500
2000
1500
1000
500
0
10
20
30
40
50
60
70
80
90
100
Percent of Maximum Workload
RESTING CONDITIONS FOR A
TYPICAL HEALTHY ADULT
VO2
Q
CaO2
CvO2
CaO2-CvO2
=
=
=
=
=
250 ml/min
5 L/min
200 ml/L of whole blood
150 ml/L of whole blood
50 ml/L of whole blood
MAXIMUM EXERCISE
RESPONSE FOR A
WORLD CLASS ATHLETE
VO2
Q
CaO2
CvO2
CaO2-CvO2
=
=
=
=
=
5000 ml/min
25 L/min
200 ml/L of whole blood
20 ml/L of whole blood
180 ml/L of whole blood
Cardiac Output
+
Heart Rate
+
Stroke Volume
+
Preload
+
-
Afterload
Contractility
Heart Rate Response to Increasing Work
200
180
160
Heart Rate
140
120
100
80
60
40
20
0
10 20 30 40 50 60 70 80 90 100
Percent of Maximium Oxygen Consumption
Maximum He art Rate and Age
220
Maximum Heart Rate
200
180
160
HRMAX = 220 - age (yrs)
140
120
100
20
30
40
50
Age (ye ars)
60
70
Stroke Volume vs Workload
Stroke Volume (mL/beat)
160
140
120
100
80
60
40
20
0
10
20
30
40
50
60
70
80
90
100
Percent Maximum Oxygen Consumption
PRELOAD
Volume of blood in the ventricle at the end of diastole
LVEDV
Venous Return
Frank-Starling Mechanism
Stroke
Volume
LVEDV
PRELOAD
Volume of blood in the ventricle at the end of diastole
LVEDV
Venous Return
Venous Tone
Skeletal Muscle
Pump
Thoraco-abdominal
Pump
Contractility
Stroke
Volume
LVEDV
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
Effective Ventilation – VD/VT
0.40
VD/VT
0.25
Rest
Max
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+
MAXIMUM EXERCISE
RESPONSE FOR A
WORLD CLASS ATHLETE
VO2
Q
CaO2
CvO2
CaO2-CvO2
=
=
=
=
=
5000 ml/min
25 L/min
200 ml/L of whole blood
20 ml/L of whole blood
180 ml/L of whole blood
MAXIMUM EXERCISE
RESULTS FOR A TYPICAL
HEALTHY ADULT
VO2
Q
CaO2
CvO2
CaO2-CvO2
=
=
=
=
=
2500 ml/min
15 L/min
200 ml/L of whole blood
33 ml/L of whole blood
167 ml/L whole blood
Principles of Physical Training
• Overload
• Specificity
• Reversibility
Training for Improved Aerobic
Endurance
•
•
•
•
Type of Exercise
Intensity
Duration
Frequency
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.
Karvonen Formula for
Prescribing Exercise Heart Rate
HREx = HRRest + 0.60 (HRMax – HRRest)
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
Effect of Conditioning on Heart Rate Response
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
Oxygen Consumption
Cardiac Output
Heart Rate
Stroke Volume
Systolic Blood Pressure
Rate-Pressure Product
Minute Ventilation
Effect
Unchanged-Decreased
Unchanged
Decreased
Increased
Decreased
Decreased
Decreased
Effects of Chronic Physical
Activity on Aerobic Function
Maximal Values
Oxygen Consumption
Cardiac Output
Heart Rate
Stroke Volume
Arteriovenous O2 Difference
Systolic Blood Pressure
Rate-Pressure Product
Ejection Fraction
Effect
Increased
Increased
Unchanged-Decreased
Increased
Increased
Unchanged
Unchanged
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
Sex
VC
IC
TLC
FEV1
FEV1/VC
MVV
Hct
75 yrs
Male
3.5L (100%)
2.3L (102%)
6.0L (110%)
3.90L (95%)
80%
100L
44%
Exercise Data
– VO2 (Peak)
– HRMAX
– SBP
–
–
–
–
VEMAX
VD/VT
P(A-a)O2
θAT
1.75L (100%)*
140 bpm
155/84
180/75
70L/min
0.35 0.25
20 torr
1.4L
*Patient stopped exercise due to dyspnea
Case #20000512
Resting Data
– Age
– Sex
– VC
– IC
– TLC
– FEV1
– FEV1/VC
– MVV
48 yrs
Male
4.75L (93%)
3.94L (95%)
5.90L (98%)
3.90L (93%)
80%
Exercise Data
– VO2 (Peak)
– HRMAX
– SBP
– VEMAX
– VD/VT
– P(A-a)O2
– θAT
1.55L(58%)*
168 bpm
150/92 205/120
48L
0.40 0.30
20 torr
1.30L
90L
* 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
Sex
VC
IC
TLC
FEV1
FEV1/VC
MVV
60 yrs
Male
3.75L (80%)
2.75L (70%)
6.53L (130%)
2.80L (65%)
60%
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
Sex
VC
IC
TLC
FEV1
FEV1/VC
MVV
– DLCO
70 yrs
Male
3.65L (78%)
2.28L (72%)
6.03L (81%)
2.20L (60%)
60%
95L
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
10.8 (35%)
* Patient stopped exercise due to extreme dyspnea
Case #2001367
Resting Data
–
–
–
–
–
–
–
–
–
Age
Sex
VC
IC
TLC
FEV1
FEV1/VC
MVV
DLCO
60 yrs
Male
1.75L (40%)
1.55L (42%)
8.03L (120%)
0.54L (15%)
30%
35L
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
Temperature Regulation
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
REGULATION OF BODY TEMPERATURE
Heat Production
Hormonal Effects
on Metabolism
Metabolism
Associated with
Muscular Activity
Basal Metabolic
Rate
Heat Loss
Radiation
Conduction
Evaporation
Blood Flow
Insulation
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 (5-20m or 1020X 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
ºF = 35.74 + 0.6215T - 35.75V(100.16) + 0.4275V(100.16)
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 Regulation
Skin 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 Regulation
Skin 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  Thyroidstimulating hormone  Thyroxine
– Stimulated by cooling of the anterior hypothalamicpreoptic area
– Requires several weeks of exposure to cold to cause
hypertrophy of the thyroid gland
Abnormalities of Body
Temperature Regulation
• Fever
– Effect of pyrogens
– Brain lesions
• Heatstroke
• Frostbite
• Malignant Hyperthermia