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Chapter 8 Responses and Adaptations of the Cardiorespiratory System Copyright © 2012 American College of Sports Medicine Anatomy of the Heart • Heart – Pump that circulates blood throughout body – Four chambers • Right & left atria: receivers • Right & left ventricles: pump blood away – 2/3 of mass on left side – Weighs 11 oz in men & 9 oz in women (proportional to body size) Copyright © 2012 American College of Sports Medicine Anatomy of the Heart (cont’d) Copyright © 2012 American College of Sports Medicine Anatomy of the Heart (cont’d) • Cardiac Musculature: Myocardium – Contracts on its own – Capable of hypertrophy & adapting to exercise – Thickness affected by stress; thicker = stronger – Larger, fewer T tubules compared with skeletal muscle – Contracts forcefully at lower rate than skeletal muscle – Cardiocytes: cardiac cells that have the ability to communicate directly with adjacent cells via intercalated discs – Intercalated discs enable rapid spread of action potentials Copyright © 2012 American College of Sports Medicine Major Blood Vessels • Arteries – High-pressure vessels that deliver oxygen-rich blood to tissues – Have walls containing smooth muscle & elastic fibers • Arterioles – Smaller arteries that constrict or relax to regulate blood flow – Branch & form smaller vessels called metarterioles • Capillaries – Thin vessels that serve as site for nutrient/oxygen exchange – 2,000 to 3,000 per square mm of tissue Copyright © 2012 American College of Sports Medicine Major Blood Vessels (cont’d) • Venules – Small veins joined to capillaries that drain blood toward heart • Veins – Vessels joined to venules that return blood to heart – Low-pressure structures with extensible walls – Storage site for blood when circulatory demands are low Copyright © 2012 American College of Sports Medicine Circulatory System Copyright © 2012 American College of Sports Medicine Regulation of the Heart • Intrinsic Regulation of the Heart – Heart can regulate its own rhythm – Sinoatrial (SA) node: pacemaker of heart • Spontaneously generates action potential • Located in right atrium – Wave of depolarization spreads across atria – Atrioventricular (AV) node: delays wave of depolarization – Bundle of His: arises from AV node & continues depolarization – Wave spreads through ventricles via bundle branches & Purkinje fibers Copyright © 2012 American College of Sports Medicine Conductive System of the Heart Copyright © 2012 American College of Sports Medicine Regulation of the Heart (cont’d) • Extrinsic Regulation of the Heart – Nervous & endocrine systems – Cardiac center in medulla oblongata controls: • Heart rate (HR) • Vessel diameter – Feedback from sensory motor centers in brain controls: • HR • Force of contraction – Role of autonomic nervous system Copyright © 2012 American College of Sports Medicine Blood Components • Plasma – 55-60% of total blood volume – Composition • 90% is water • 7% is plasma proteins • 3% is nutrients & waste Copyright © 2012 American College of Sports Medicine Blood Components (cont’d) • Formed Elements – 40-45% of total blood volume – Hematocrit: % of formed elements relative to total blood vol. – Composition • 99% red blood cells (RBCs) • 1% white blood cells (WBCs) & platelets – RBCs: transport oxygen bound to iron-containing protein hemoglobin – Platelets: small molecules required for blood clotting – WBCs: critical to immune function Copyright © 2012 American College of Sports Medicine Oxygen-Hemoglobin Dissociation Curve Copyright © 2012 American College of Sports Medicine Partial Pressure of Oxygen and Carbon Dioxide Copyright © 2012 American College of Sports Medicine Blood Components (cont’d) • Blood Flow – Body contains about 5 L of blood – Distribution • 15-20% to skeletal muscle • 25% to liver • 20% to kidneys • 10% to skin • 14-15% to brain • 10-12% to heart & other tissues Copyright © 2012 American College of Sports Medicine Blood Components (cont’d) • Blood Flow (cont’d) – Blood flow to skeletal muscle increases to >80% of total flow to meet metabolic demands – Skeletal muscle contraction pumps venous blood back to heart – Venous valves prevent backward flow of blood in veins – Ischemia associated with RT is stimulus for muscle hypertrophy – Tightly regulated Copyright © 2012 American College of Sports Medicine Cardiovascular Function • CV Variables – Heart rate: frequency of heart beats per min – Blood pressure: pressure in arteries after left ventricle contracts – Systolic blood pressure • Pressure in left ventricle during systole • Averages 120 mm Hg – Diastolic blood pressure • Peripheral resistance to flow during relaxation (diastole) • Averages 80 mm Hg Copyright © 2012 American College of Sports Medicine Cardiovascular Function (cont’d) • CV Variables (cont’d) – Stroke volume: blood vol. ejected from left ventricle each beat – Cardiac output: total volume of blood pumped by heart per min Copyright © 2012 American College of Sports Medicine Cardiovascular Responses to Exercise • Heart Rate (HR) Response – Increases during exercise from resting values to rates >195 bpm – Upper limits for HR during exercise: • 220 − person’s age in years = HR max • Target range is based on % of HR max – Magnitude of HR increase depends on muscle mass use, exercise intensity, & degree of continuity of exercise – HR increases linearly up to maximal Copyright © 2012 American College of Sports Medicine Cardiovascular Responses to Exercise (cont’d) • Stroke Volume (SV) Response – Increases during exercise from resting values to rates >195 bpm – Magnitude of SV increase determined by: • Blood volume returning to heart • Arterial pressure • Ventricular contractility • Distensibility – Increases linearly up to about 40-60% of maximal exercise capacity Copyright © 2012 American College of Sports Medicine Cardiovascular Responses to Exercise (cont’d) • Cardiac Output (Qc) – Is product of HR & SV – Increases linearly during aerobic exercise – May increase to 20-40 L min-1 depending on fitness level – Increases over course of workout during RT Copyright © 2012 American College of Sports Medicine Cardiac Output Response to Aerobic Exercise Copyright © 2012 American College of Sports Medicine Cardiovascular Responses to Exercise (cont’d) • Blood Pressure (BP) – Increases during exercise – Increases during RT with increase proportional to effort – Muscle mass activation plays a role Copyright © 2012 American College of Sports Medicine BP Response to 3 Sets of Leg Press Copyright © 2012 American College of Sports Medicine Cardiovascular Responses to Exercise (cont’d) • Plasma Volume – Decreases during exercise – Decreases up to 20% during endurance exercise – Reductions can impair endurance performance & VO2max – Decreased by 7-14% immediately after resistance exercise Copyright © 2012 American College of Sports Medicine Cardiovascular Responses to Exercise (cont’d) • Oxygen Consumption – Increases proportionally during exercise in relation to: • Intensity • Muscle mass activation • Degree of continuity – Represented by Fick equation: • VO2 = Qc × A-VO2 difference Copyright © 2012 American College of Sports Medicine The A-VO2 Difference Copyright © 2012 American College of Sports Medicine Relationship Between Exercise Intensity and Oxygen Consumption Copyright © 2012 American College of Sports Medicine Chronic Adaptations at Rest and During Exercise • Pressure Overload – Results from rise in BP & intrathoracic pressure that accompany exercise – Can alter several CV variables positively over time • Volume Overload – Results from greater venous return & blood flow to heart during exercise – Aerobic exercise is superior due to higher level of continuity – Leads to positive changes in several CV variables – Increases cardiac chamber size Copyright © 2012 American College of Sports Medicine Chronic Adaptations at Rest and During Exercise (cont’d) • Cardiac Dimensions – Adaptations governed by Law of Laplace: • Wall tension is proportional to pressure & size of radius of curvature – Greater heart size is characterized by greater left ventricular cavity & thickening of cardiac walls – Aerobic training leads to improvements in cardiac function – RT leads to changes in left-side cardiac muscularity – RT elicits very small to no changes in left ventricular cavity size Copyright © 2012 American College of Sports Medicine Chronic Adaptations at Rest and During Exercise (cont’d) • Cardiac Output (Qc) – Qc response to exercise is augmented – Aerobic training reduces resting HR – Resting SV may slightly increase or not change during RT – Resting HR may not change or slightly decrease during RT Copyright © 2012 American College of Sports Medicine Heart Rate Response During Exercise Before and After Training Copyright © 2012 American College of Sports Medicine Chronic Adaptations at Rest and During Exercise (cont’d) • VO2max – Gold standard of aerobic fitness – Increases during training due to increases in SV, Qc, & small increase in A-VO2 difference – Increases 10-30% with aerobic training during first 6 months – Increases only minimally with anaerobic training Copyright © 2012 American College of Sports Medicine Comparison of VO2max Data From Different Male Athletes Copyright © 2012 American College of Sports Medicine Chronic Adaptations at Rest and During Exercise (cont’d) • Blood Pressure – Decreased systolic & diastolic BP with aerobic training – Largest reductions seen in hypertensive people – Not affected or reduced with RT Copyright © 2012 American College of Sports Medicine Chronic Adaptations at Rest and During Exercise (cont’d) • Blood Volume – Increased with aerobic training, mostly due to increase in plasma – Plasma volume increases 12-20% within first few weeks of AT – Endurance athletes have blood volumes about 35% greater than untrained people – RT may have limited effect Copyright © 2012 American College of Sports Medicine Chronic Adaptations at Rest and During Exercise (cont’d) • Blood Lipids and Lipoproteins – Major factors in CV health – Include triglycerides, cholesterol, LDL-C, VLDL-C, HDL-C, & lipoprotein A – Factors affecting: genetics, diet, stress, smoking, body weight, & exercise – Increased HDL-C, decrease in other lipids with AT – RT has no or very small effects in improving lipid profiles Copyright © 2012 American College of Sports Medicine Respiratory System • Overview – Essential for introducing oxygen into the body & removing CO2 – Respiration includes: • Breathing • Inspiration: breathing in • Expiration: breathing out • Pulmonary diffusion • Oxygen transport • Gas exchange Copyright © 2012 American College of Sports Medicine The Human Respiratory System Copyright © 2012 American College of Sports Medicine Respiratory System (cont’d) • Lung Volumes and Capacities – Tidal volume: volume of air inspired or expired every breath – Inspiratory reserve volume: volume of air inspired after normal tidal volume – Expiratory reserve volume: volume of air expired after normal tidal volume – Residual volume: volume of air left in lungs after maximal expiration – Total lung capacity: volume of air in lungs after maximal inspiration Copyright © 2012 American College of Sports Medicine Respiratory System (cont’d) • Lung Volumes and Capacities (cont’d) – Forced vital capacity: maximal volume of air expired after maximal inspiration – Inspiratory capacity: maximal volume of air after tidal volume expiration – Functional residual capacity: volume of air in lungs after tidal volume expiration – Forced expiratory volume: volume of air maximally expired forcefully in 1 second after maximal inhalation – Maximum voluntary ventilation: maximum volume of air breathed rapidly in 1 minute – Minute ventilation: volume of air breathed per minute Copyright © 2012 American College of Sports Medicine Respiratory System (cont’d) • Control of Breathing – Involuntary, but can be controlled voluntarily to some extent – Neural & hormonal factors – Circulatory (humoral factors) – Rapid increase in ventilation during exercise, followed by slower rise as exercise progresses Copyright © 2012 American College of Sports Medicine Overview of Respiratory Control Copyright © 2012 American College of Sports Medicine Pulmonary Ventilation During Exercise Copyright © 2012 American College of Sports Medicine Respiratory System (cont’d) • Pulmonary Adaptations to Training – Little change in lung volumes & capacities with AT • Ventilatory Muscle-Specific Training – Involves RT during respiration – Used to increase respiratory function by improving strength & endurance of inhalation muscles Copyright © 2012 American College of Sports Medicine