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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 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+ 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 Physical Performance Capacity Environment Temperature Altitude Inhaled Gases 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 versus VO Max • Peak VO2 • Respiratory 2 – 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) 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 – Sex – VC – IC – TLC – FEV1 – FEV1/VC – MVV 48 yrs Male 4.75L (93%) 3.94L (95%) 5.90L (98%) 3.90L (93%) 80% 90L 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 * 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 (6%) 60% 95L 10.8 (35%) Exercise Data – VO2 (Peak) – HRMAX – SBP – – – – – VEMAX VD/VT P(A-a)O2 PaO2 θAT 1.32L (65%)* 152 bpm 175/86 227/90 90L/min 0.45 0.48 45/68 torr 64/52 torr 0.95L * 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 (5-20m 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