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Cardiovascular Response to Exercise
- 2. HEART RATE • Reflects the amount of work the heart must do to meet increased demand • Resting Heart Rate – Averages 60 - 80 b/min – 30 (highly trained) to 100 (sedentary) – anticipatory response • Exercise Heart Rate – linear relationship with Oxygen Uptake & Workload
- 3. • Maximum Heart Rate (MHR) – highest heart rate you achieve in an all- out effort – estimated by MHR = 220 - age • Steady State Heart Rate – optimal heart rate for meeting the circulatory demands at a specific work rate – can increase during prolonged exercise & heat stress – indication of fitness level
- 4. BLOOD PRESSURE • Systolic –Increases with workload • Diastolic Increases, decreases, or stays the same + 10 mm Hg
- 5. STROKE VOLUME • DETERMINED BY – Volume of venous return – Ventricular Distensibility – Ventricular Contractility – Aortic or Pulmonary Artery Pressure
- 6. STOKE VOLUME INCREASES WITH EXERCISE • Almost doubles until 40 - 60% of maximal capacity • Mechanisms of Increase – Frank-Starling Mechanism • greater ventricular stretch = greater ventricular contraction – Increased Ventricular Contractility via stimulation
- 7. CARDIAC OUTPUT • Linear Relationship between cardiac output and work rate/oxygen consumption • Effort to meet the muscles’ increased demand for oxygen
- 8. REDISTRIBUTION OF BLOOD FLOW • At Rest 15-20% of Q goes to skeletal muscle • During heavy Exercise this increases to 80 to 85% • Redirected through action of the sympathetic nervous system • Overall Vasoconstriction & Local Vasodialation
- 9. Control of Pulmonary Ventilation During Exercise • Immediate-Marked Increase – Initiated by Motor Cortex – Assisted by feedback from working muscle • More Gradual Rise – Result of changes in Temperature and Chemical Status (i.e. chemoreceptors) – Levels off between 100-160 L.min-1 • Recovey Mirrors Exercise
- 10. Breathing Problems During Exercise • Dyspnea – shortness of breath • Hypeventilation – sometimes intentional • Valsalva Maneuver – Closes Glottis – Increased intra-abdominal and intra-thoracic pressures – reduces volume of blood returned to the heart – increases TPR
- 11. Ventilatory Breakpoint • Disproportionate Increase in VE as compared to increase in VO2 • Result of accumulation of H+ and CO2 in blood • Sometimes observed in VE/VO2 measure • The same as Anaerobic Threshold ?
- 12. Ventilation Limiting Performance • Typically not in Normals • Possibly in Highly Trained Subjects • Likely in COPD • Environment can influence the role of ventilation in performance
- 13. CARDIORESPIRATORY ENDURANCE • THE ABILITY OF THE BODY TO SUSTAIN PROLONGED EXERCISE
- 14. MAXIMAL OXYGEN CONSUMPTION • VO2max = Aerobic Power • Highest Rate of Oxygen Consumption attainable during maximal exercise • “Gold-Standard” of assessing Fitness Level
- 15. VO2max • VO2 increases with increasing workload until plateau • Average 20% increase following 6 month training program in previously untrained • Absolute = L.min-1 • Relative = ml.kg-1.min-1
- 16. • Average College-Aged Female = 40-45 ml.kg-1.min-1 • Average College-Aged Male = 45-50 ml.kg-1.min-1 • Highly-Trained Female = 60-70 ml.kg-1.min-1 • Highly-Trained male = 65-75 ml.kg-1.min-1 VO2max
- 17. Fick Equation VO2 = SV X HR X a-vO2diff
- 18. HEART SIZE • Increased Heart Weight and Volume • Increased Left Ventricle wall thickness and chamber size • Athlete’s Heart • Endurance versus Resistive Exercise
- 19. Training and Heart Rate • Resting Heart Rate – decreases markedly (1 beat per min per week) – increased parasympathetic, decreased sympathetic • Submaximal Heart Rate – lower heart rates at a specified work rate – heart becomes more efficient • Maximum Heart Rate – may decrease slightly
- 20. Stroke Volume • Increase in Both Resting and Maximal SV • Due to: –Increase in Plasma Volume –Increase in Elastic Recoil of LV –Increase in LV contractility
- 21. Untrained 55-75 80-110 Trained 80-90 130-150 Highly Trained 100-120 160-220+ SV Rest (ml) Max SV (ml)
- 22. Heart Rate Recovery • Heart Rate Recovery Period is shortened by training • Can be used as an index of cardiorespiratory fitness • Effected by heat stress & altitude
- 23. Cardiac Output • During Resting and at Absolute Submaximal Workloads it doesn’t change much • Increases significantly at maximal exercise • Mainly due to increase in maximal Stroke Volume
- 24. Blood Flow • Increased capillarization of trained muscle > capillary to fiber ratio • Greater Opening of Existing Capillaries • More effective blood Redistribution
- 25. Blood Pressure • Changes little during standardized submaximal and maximal exercise • “Exercise Only” typically has little effect on Resting Blood Pressure • Weight is more of an issue • Borderline Hypertensive’s • Aerobic vs Resistive Exercise Training
- 26. Blood Volume • Exercise Training increases Blood Volume • Due to Increase in Plasma Volume • Two Mechanisms – Increased release of Antidiuretic Hormone (ADH) and Aldosterone – Increased amount of plasma proteins (Albumin)
- 27. Red Blood Cells • Hematocrit is Typically Reduced – reduces viscosity of blood – A cause for anemia ? – Effect on Performance • Absolute amount of Red Blood Cells and Hemoglobin Increases • Blood Doping
- 29. Respiratory Adaptations • Lung Volumes – Vital Capacity slightly – Residual Volume slightly – Tidal Volume • Respiratory Rate – Lowered at Rest and Standardized Submaximal Workloads – Increased at MAX • Pulmonary Ventilation – Maximal is greatly increased • Pulmonary Diffusion – Increased during maximal exercise – Better Pulmonary Blood Flow
- 30. Arterial-Venous Oxygen Difference • Increases with training particularly at Maximal levels • Lower Mixed Venous Content • Due to: – Greater Oxygen Extraction – More Effective Blood Distribution
- 31. Lactate Threshold • Increased - Able to perform at a higher rate of work without increasing Blood Lactate Levels above Resting • Due to: > ability to clear lactate Shift in preference for metabolic substrates
- 32. Resting Oxygen Consumption • Typically Increased Slightly • Due to: – Increased Muscle Mass – EPOC • Return to Homeostasis • Thermoregulation • Clearance of Waste Products • Adaptations
- 33. Submaximal Oxygen Consumption • Locomotive Economy/Running Economy • Elite versus Novice – Shows improvement • Longitudinal Data – Shows no change • What is Going On ? – Becoming more skilled – Becoming more efficient physiologically – Shifting Substrate Utilization to Fat
- 34. Maximal Oxygen Consumption • Initial Level of Conditioning – the higher the initial state the lesser the increase – Highest attainable VO2max reached in 8 to 18 months • Reasons for Increased VO2max – Increased Oxidative Enzymes in the Muscle – Improved Delivery of Oxygen to the Muscles • i.e. improved blood flow
- 35. Factors Affecting the Response to Aerobic Training • Heredity – responders versus nonresponders • Age • Gender • Specificity of Training
- 38. Abnormal Heart Rate Responses • Low Resting Heart Rate (50-70 bpm) • Symptom Limited Max HR well below predicted • Poor, slow heart rate increase in response to increasing exercise workloads • Be aware of effects Chronotropic- Inhibiting Agents
- 39. Mechanisms of Abnormal HR Responses • Ischemia of SA Node • Decrease in Myocardial Contractility – with increased Ischemia
- 40. Abnormal* Well-Trained Normal * Ominous sign of advanced CAD associated with accelerated rates of mortality & Morbibity Workload Heart Rate
- 41. Abnormal Falling Normal Workload Systolic BP * Care should be taken not to overinterpret an abnormal response Abnormal
- 42. Symptoms Associated With Fall in Systolic Blood Pressure • Shortness of Breath • ST Segment Changes • Angina • Pallor
- 43. Mechanisms of Abnormal BP Response • Ischemic of Scarred Ventricle will quickly achieve maximal SV • Consequently, Cardiac Output will not increase as much • As a result SBP may decrease due to reduced Periferal Vascular Resistance
- 44. Diastolic BP Abnormality • Persistent Rise in Diastolic Pressure with increases in exercise workloads – 15-20 mm Hg or greater – May Be indicative of CAD without ECG changes – Reduced Coronary Artery Blood Flow • Drop in Diastolic Pressure