C H A P T E R 9 CARDIOVASCULAR AND RESPIRATORY ADAPTATIONS TO TRAINING Learning Objectives w Learn how cardiorespiratory endurance differs from muscular endurance. w Review how cardiorespiratory endurance is measured. w Find out what changes occur in the oxygen transport system as a result of endurance training. w Examine metabolic adaptations that occur due to endurance training. (continued) Learning Objectives w Discover how adaptations to cardiovascular, respiratory, and metabolic function affect an athlete's endurance capacity. w Learn why cardiorespiratory adaptations benefit performance in both endurance and nonendurance sports. Endurance Training Muscular Endurance w Ability of a single muscle or muscle group to sustain high-intensity, repetitive, or static exercise that occurs in repeated 1- to 2-minute bursts w Related to muscular strength and anaerobic development Cardiorespiratory Endurance w Ability of the whole body to sustain prolonged, steady-state exercise w Related to cardiovascular and respiratory system (aerobic) development Evaluating Endurance Capacity VO2max w Highest rate of oxygen consumption attainable during maximal exercise w Can be increased with endurance training . Submaximal Endurance Capacity w Closely related to competitive endurance performance; determined by VO2max and lactate threshold w More difficult to evaluate since there is no one physiological variable that can be measured to quantify it w Can also be increased with endurance training . CHANGES IN VO2MAX WITH TRAINING . Parameters Affected by Training w Heart size w Stroke volume w Heart rate w Cardiac output w Blood flow w Blood pressure w Blood volume Oxygen Transport System w Components of the cardiorespiratory system that transport O2 to and from active tissues w Can transport O2 more efficiently with adaptations that occur with endurance training w Evaluated with the Fick equation: VO2 = SV ´ HR ´ a-vO2 diff . – DIFFERENCES IN HEART SIZE DIFFERENCES IN HEART SIZE DIFFERENCES IN HEART SIZE Key Points w The left ventricle changes the most in response to endurance training. w The internal dimensions of the left ventricle increase mostly due to an increase in ventricular filling. Heart Size Adaptations w The wall thickness of the left ventricle increases, allowing a more forceful contraction of the left ventricle. MEASURING HEART SIZE STROKE VOLUME AND TRAINING Stroke Volumes (SV) for Different States of Training Untrained 50-70 80-110 Trained 70-90 110-150 Highly trained 90-110 150-220 Subjects SVrest (ml) SVmax (ml) DIFFERENCES IN EDV, ESV, AND EF Key Points w Endurance training increases SV at rest and during submaximal and maximal exercise. w End diastolic volume increases, caused by an increase in blood plasma and greater diastolic filling time, contributing to increased SV. Stroke Volume Adaptations w The increased size of the heart allows the left ventricle to stretch more and fill with more blood; wall thickness increases enhance contractility. Reduced systemic blood pressure lowers the resistance to the flow of blood pumped from the left ventricle. HEART RATE AND TRAINING Resting Heart Rate w Decreases with endurance training likely due to more blood returning to heart and changes in autonomic control w Sedentary individuals can decrease RHR by 1 beat/min per week during initial training, but several recent studies have shown small changes of less than 3 beats/min with up to 20 wk of training w Highly trained endurance athletes may have resting heart rates of 30 to 40 beats/min Heart Rate During Exercise Submaximal w Decreases proportionately with the amount of training completed w May decrease by 10 to 30 beats/min after 6 months of moderate training at any given rate of work, with the decrease being greater at higher rates of work Maximal w Remains unchanged or decreases slightly w A decrease might allow for optimal stroke volume to maximize cardiac output Does increased stroke volume allow a decreased heart rate or does decreased heart rate allow an increased stroke volume? Which Comes First? Heart Rate Recovery Period w The time after exercise that it takes your heart to return to its resting rate w With training, heart rate returns to resting level more quickly after exercise w Has been used as an index of cardiorespiratory fitness w Should not be used to compare individuals to one another w Conditions such as altitude or heat can affect it HEART RATE RECOVERY AND TRAINING Resistance training can lead to decreases in heart rate; however, these decreases are not as reliable or as large as those that occur due to endurance training. Did You Know…? Key Points Cardiac Output Adaptations w Q decreases slightly or does not change at rest or during submaximal exercise. . w Q increases dramatically at maximal exertion due to the increase in maximal SV. . w A slight decrease could be the result of an increase in the a-vO2 diff due to greater oxygen extraction by the tissues or to a reduction in the requirement for oxygen. – w Absolute values of Qmax range from 14 to 20 L/min in untrained people, 25 to 35 L/min in trained individuals, and 40 L/min or more in large endurance athletes. . CARDIAC OUTPUT AND TRAINING Blood Flow Increases With Training w Increased capillarization of trained muscles (higher capillary-to-fiber ratio) w Greater opening of existing capillaries in trained muscles w More effective blood redistribution—blood goes where it is needed w Increased blood volume Key Points w Endurance training results in reduced blood pressure at the same submaximal work rate, but at maximal work rates systolic pressure increases and diastolic pressure decreases. w Resting blood pressure (both systolic and diastolic) is lowered with endurance training in individuals with borderline or moderate hypertension. Blood Pressure and Training w Blood pressure during lifting heavy weights can cause marked increases in systolic and diastolic blood pressure, but resting blood pressure after resistance training tends to not change and may decrease. BLOOD VOLUME AND TRAINING Key Points w Endurance training, especially intense training, increases blood volume. w Blood volume increases due primarily to an increase in plasma volume (increases in ADH, aldosterone, and plasma proteins cause more fluid to be retained in the blood). Blood Volume and Training w Red blood cell volume increases, but increase in plasma volume is higher; thus, hematocrit decreases. w Blood viscosity decreases, thus improving circulation and enhancing oxygen delivery. w Changes in plasma volume are highly correlated with changes in SV and VO2max. . BLOOD AND PLASMA VOLUME AND TRAINING Cardiovascular Adaptations to Training w Left ventricle size and wall thickness increase w Resting, submaximal, and maximal stroke volume increases w Maximal heart rate stays the same or decreases w Cardiac output is better distributed to active muscles and maximal cardiac output increases w Blood volume increases, as does red cell volume, but to a lesser extent w Resting blood pressure does not change or decreases slightly, while blood pressure during submaximal exercise decreases Key Points w Pulmonary diffusion increases at maximal work rates. Respiratory Adaptations to Training w The respiratory system is seldom a limiter of endurance performance. w All the major adaptations of the respiratory system to training are most apparent during maximal exercise. w The a-vO2 diff increases with training due to more oxygen being extracted by tissues. – w Pulmonary ventilation increases during maximal effort after training; you can improve performance by training the inspiratory muscles. Did You Know…? Although the largest part of the increase in VO2max results from the increases in cardiac output and muscle blood flow, the increase in a-vO2 diff also plays a key role. This increase in a-vO2 diff is due to a more effective distribution of arterial blood away from inactive tissue to the active tissue, so that more of the blood coming back to the right atrium has gone through active muscle. . – – Metabolic Adaptations to Training Lactate threshold increases. Respiratory exchange ratio w decreases for submaximal efforts (greater use of FFAs), and w increases at maximal levels. . Oxygen consumption (VO2) is w unaltered or slightly increased at rest, w unaltered or slighted decreased at submaximal rates of work, and . w increased at maximal exertion (VO2max—increases range from 0% to 93%). CHANGE IN RACE PACE, NOT VO2MAX . Did You Know…? Once an athlete has achieved her genetically determined peak VO2max, she can still increase her endurance performance due to the body's ability to perform at increasingly higher percentages of that VO2max for extended periods. The increase in performance without an increase in VO2max is a result of an increase in lactate threshold. . . . VO2MAX COMPARISON IN BROTHERS . Level of conditioning—the greater the level of conditioning the lower the response to training Sex—lower in women than men (20% to 25% lower in untrained women; 10% lower in highly trained women) Specificity of training—the closer training is to the sport to be performed, the greater the improvement and performance in that sport Factors Affecting VO2max . Heredity—accounts for slightly less than 50% of the variation as well as an individual’s response to training Age—decreases with age are associated with decreases in activity levels as well as decreases in physiological function VO2MAX CHANGES AND AGE . IMPROVEMENT IN VO2MAX WITH TRAINING . INCREASE IN VO2MAX FOR TWINS . VO2MAX AND SPECIFICITY OF TRAINING . Cardiorespiratory Endurance Training w Major defense against fatigue which limits optimal performance. w Should be the primary emphasis of training for health and fitness. w All athletes can benefit from maximizing their endurance. MODELING ENDURANCE PERFORMANCE