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Exercise Physiology Cardiorespiratory Physiology Cardiovascular System • Functions: • Supply muscles & organs with oxygen • Deliver nutrients to muscles & organs • Remove metabolic by-products from active tissues • Like??? • Functions accomplished due to blood Heart Structure • 4 Chambers: • 2 Atria- receive blood from body; upper chambers • 2 Ventricles- send blood to body; lower chambers • Right & Left Sides: • Right- receives from body & sends blood to lungs; deoxygenated blood • Left- receives from lungs & sends blood to body; oxygenated blood Heart Structure Blood Vessels & Blood • 3 Major Types: 1. Arteries: carry blood away from the heart 2. Capillaries: site of substance exchange 3. Veins: carry blood back to the heart Blood Vessels & Blood • Red blood cells contain hemoglobin • Molecule made of protein & iron • Capable of bonding to & transporting 4 oxygen molecules • Amount of oxygen being transported is dependent upon partial pressure of oxygen (PO2) • In lungs, PO2 is high, oxygen binds easily • Near tissues in body, PO2 is low, oxygen unloads & allows diffusion Cardiorespiratory Connection http://www.youtube.com/watch?v=mH0QTWzU-xI Respiratory System • Functions: • Deliver oxygen to the blood • Remove carbon dioxide from the blood • Aid in acid-base (pH) balance of the blood Respiratory Structures • Nose & Mouth: • Filter, humidify, & adjusts temperature of air • Trachea: • Passageway for air only • Bronchi: • Tubes that allow air to enter the lungs Respiratory Structures • Lungs: • Right (larger) & Left • Divided into lobes • Soft & spongy • Contain alveoli • Alveoli • Tiny air sacs • Site of gas exchange (diffusion) • Movement of molecules from areas of high concentration to low concentration until equilibrium Respiratory Structures Ventilation • 2 phases: • Inspiration- movement of air into the lungs • Expiration- movement of air out of the lungs • http://glencoe.mcgrawhill.com/sites/9834092339/student_view0/chapter49/a lveolar_pressure_changes_during_inspiration_and_e xpiration.html Ventilation • Breathing rate & depth increases with exercise • Why? • Not due to need for more oxygen • Due to need to rid body of carbon dioxide & maintain blood pH • Allows for more gas exchange to occur • Efficiency of gas exchange increases Gas Exchange Measuring Heart Rate • Heart Rate (HR) • Number of times the heart beats in 1 minute • Units = bpm (beats per minute) • Resting HR • 40 bpm – 70 bpm • Heart Rate changes due to body’s need to eliminate CO2 • CO2 becomes carbonic acid in the blood & alters pH • Exercise HR can be 200+ bpm Measuring Heart Function • Stroke Volume: • The amount of blood pumped out of the left ventricle with each heartbeat • Units = mL or L • Cardiac Output: • The amount of blood pumped into the aorta each minute • Units = mL or L per minute • Cardiac output = stroke volume x heart rate Measuring Blood Pressure • Normal = 120/80 mm Hg • Systolic pressure • Estimates the heart’s work & pressure against walls of arteries • Occurs during ventricular contraction • Diastolic pressure • Indicates the blood pressure in the body outside of the heart • Occurs during ventricular relaxation Measuring Cardiorespiratory Function VO2 Max: maximal volume of oxygen that can be consumed in a given amount of time during maximal effort Measures aerobic power Units = mL of oxygen/kg of body wt/min VO2 Max Peaks between 18-25 years of age Sedentary but healthy 20 year old… Male: ~40 ml/kg/min Female: ~36 ml/kg/min Trained athletes… Male: 80-90 ml/kg/min Female: 75-85 ml/kg/min Measuring Cardiorespiratory Function • Arterial-Venous Oxygen Difference (a-v O2 difference) • Difference in the amount of oxygen present in the blood when it leaves the lungs and when it returns to the lungs • Increase in this value reflects more oxygen use • Example: • At rest = 4-5 mL O2 /100 mL of blood • During exercise = 15 mL O2 /100 mL of blood Immediate Response to Exercise • Heart Rate: Increases • Blood Pressure: • Systolic increases • Diastolic no change • Stroke Volume: Increases (to a point) • Cardiac Output: Increases • a-v O2 difference: Increases Immediate Response to Exercise • Bohr Effect • Exercise causes body temperature to rise • Hemoglobin is less effective at holding onto oxygen • Results in more oxygen being released to working tissues Training (Long Term) Effects • Increased heart size • Larger atria & ventricles • Thicker heart wall • Increases rate of contraction & volume of blood emptied from chambers per beat • Results in: • Decreased resting heart rate • Increased stroke volume • Increased cardiac output Training (Long Term) Effects • Increased capillarization • Improved substance exchange • Reduced risk of cardiac disease & heart attack • Improvements in a-v O2 difference • Oxygen extraction from blood improved • Increases # and activity of mitochondria • More oxidative phosphorylation Training (Long Term) Effects • Increase total blood volume • Hormone erythropoietin (EPO) stimulates red blood cell production • Results in: • Increased amount of oxygen carried by blood • Increased oxygen extraction by muscles • Altitude Training Prescribing Cardiorespiratory Exercise • Maximum HR • 220-Age (in years) • Exercise intensity is often prescribed as a % of max HR • Recommendation for typical sedentary adults 70-85% max HR • Changes to this range (above, below or within) are based on goals for exercise • Relationship between intensity & duration of exercise? Prescribing Cardiorespiratory Exercise Intensity % max HR Comments Very Light < 50% Often prescribed for elderly exercisers Light 50-63% Recovery Moderate 64-76% Builds endurance; burns more fat Hard 77-93% Appropriate for younger, more physically fit individuals; burns more carbohydrates Very Hard >94% Should only be used for interval training; cannot be maintained for long periods of time Maximal 100% Should not be used