chapter 10 Adaptations to Aerobic and Anaerobic Training

Learning Objectives Learn how cardiorespiratory endurance differs from muscular endurance Learn about the cardiorespiratory adaptations to endurance training Find out what changes occur in the oxygen transport system as a result of endurance training (continued)

Learning Objectives (continued) Examine metabolic adaptations that occur with endurance training Learn how cardiorespiratory and metabolic adaptations benefit performance in both endurance and nonendurance sports (continued)

Learning Objectives (continued) Find out how training can maximize our energy systems and our potential to perform Learn the differing adaptations that occur with aerobic and anaerobic training Find out how specific types of aerobic and anaerobic training can improve performance

Aerobic and Anaerobic Training Aerobic (endurance) training Improved central and peripheral blood flow Enhances the capacity of muscle fibers to generate ATP Anaerobic training Increased short-term, high-intensity endurance capacity Increased anaerobic metabolic function Increased tolerance for acid–base imbalances during highly intense effort

Endurance Muscular endurance: the ability of a single muscle or muscle group to sustain high-intensity repetitive or static exercise Cardiorespiratory endurance: the entire body’s ability to sustain prolonged, dynamic exercise using large muscle groups

Evaluating Cardiorespiratory Endurance . VO2max Highest rate of oxygen consumption attainable during maximal exercise VO2max can be increased by 10-15% with 20 weeks of endurance training .

Increases in VO2max With Endurance Training . Increases in VO2max With Endurance Training Fick equation: VO2 = SV  HR  (a-v)O2 diff .

Changes in VO2max With 12 Months of Endurance Training . Changes in VO2max With 12 Months of Endurance Training

Cardiovascular Adaptation to Training Heart size Stroke volume Heart rate Cardiac output Blood flow Blood pressure Blood volume

Percentage Differences in Heart Size Among Three Groups of Athletes Compared With Untrained Group

Heart Size (Central) Adaptation to Endurance Training Key Points The left ventricle changes significantly in response to endurance training The internal dimensions of the left ventricle increase as an adaptation to an increase in ventricular filling secondary to an increase in plasma volume and diastolic filling time Left ventricular wall thickness and mass increase, allowing for greater contractility

Measuring Heart Size: Echocardiography © Tom Roberts

Changes in Stroke Volume With Endurance Training

Stroke Volume Adaptations to Endurance Training Key Points Endurance training increases SV at rest and during submaximal and maximal exercise Increases in end-diastolic volume, caused by an increase in blood plasma and greater diastolic filling time (lower heart rate), contribute to increased SV Increased ventricular filling (preload) leads to greater contractility (Frank-Starling mechanism) Reduced systemic vascular resistance (afterload)

Heart Rate Adaptations to Endurance Training Resting Decreases by ~1 beat/min with each week of training Increased parasympathetic (vagal) tone Submaximal Decreases heart rate for a given absolute exercise intensity Maximal Unchanged or decreases slightly

Changes in Heart Rate With Endurance Training

Heart Rate Recovery The time it takes the heart to return to its resting rate after exercise Faster rate of recovery after training Indirect index of cardiorespiratory fitness Prolonged by certain environments (heat, altitude) Can be used as a tool to track the progress of endurance training

Changes in Heart Rate Recovery With Endurance Training

Cardiac Output Adaptations to Endurance Training . Q = HR x SV Does not change at rest or during submaximal exercise (may decrease slightly) Maximal cardiac output increases due largely to an increase in stroke volume

Changes in Cardiac Output With Endurance Training

Cardiac Output Adaptations Key Points Q does not change at rest or during submaximal exercise after training (may decrease slightly) Q increases at maximal exercise and is largely responsible for the increase in VO2max Increased maximal Q results from the increase in maximal SV . . . .

Blood Flow Adaptations to Endurance Training Blood flow to exercising muscle is increased with endurance training due to: Increased capillarization of trained muscles Greater recruitment of existing capillaries in trained muscles More effective blood flow redistribution from inactive regions Increased blood volume Increased Q .

Blood Pressure (BP) Adaptations to Endurance Training Resting BP decreases in borderline and hypertensive individuals (6-7 mmHg reduction) Mean arterial pressure is reduced at a given submaximal exercise intensity (↓ SBP, ↓ DBP) At maximal exercise (↑ SBP, ↓ DBP)

Blood Volume (BV) Adaptations to Endurance Training BV increases rapidly with endurance training Plasma volume increases due to: Increased plasma proteins (albumin) Increased antidiuretic hormone and aldosterone Red blood cell volume increases Hemoglobin increases

Increases in Total Blood Volume and Plasma Volume With Endurance Training

Blood Flow, Pressure, and Volume Adaptations to Endurance Training Key Points Blood flow to active muscles is increased due to: ↑ Capillarization ↑ Capillary recruitment More effective redistribution ↑ Blood volume Blood pressure at rest as well as during submaximal exercise is reduced, but not at maximal exercise (continued)

Blood Flow, Pressure, and Volume Adaptations to Endurance Training (continued) Key Points Blood volume increases Plasma volume increases through increased protein content and by fluid conservation hormones Red blood cell volume and hemoglobin increase Blood viscosity decreases due to the increase in plasma volume

Respiratory Adaptations to Endurance Training Key Points Little effect on lung structure and function at rest Increase in pulmonary ventilation during maximal exercise ↑ Tidal volume ↑ Respiratory rate Pulmonary diffusion increases at maximal exercise due to increased ventilation and lung perfusion (a-v)O2 difference increases with training, reflecting increased extraction of oxygen at the tissues

Adaptations in Muscle to Endurance Training Increased size (cross-sectional area) of type I fibers Transition of type IIx → type IIa fiber characteristics Transition of type II → type I fiber characteristics Increased number of capillaries per muscle fiber and for a given cross-sectional area of muscle Increased myoglobin content of muscle by 75% to 80% Increased number, size, and oxidative enzyme activity of mitochondria

Change in Maximal Oxygen Uptake and SDH Activity With Endurance Training

Gastrocnemius Oxidative Enzyme Activities of Untrained (UT) Subjects, Moderately Trained (MT) Joggers, and Highly Trained (HT) Runners Adapted, by permission, from D.L. Costill et al., 1979, "Lipid metabolism in skeletal muscle of endurance-trained males and females," Journal of Applied Physiology 28: 251-255 and from D.L. Costill et al., 1979, "Adaptations in skeletal muscle following strength training," Journal of Applied Physiology 46: 96-99.

Adaptations in Muscle With Training Key Points Type I fibers tend to enlarge Increase in type I fibers and a transition from type IIx to type IIa fibers Increased number of capillaries supplying each muscle fiber Increase in the number and size of muscle fiber mitochondria Oxidative enzyme activity increases Increased capacity of oxidative metabolism

Metabolic Adaptations to Training Lactate threshold increases due to: Increased clearance and/or decreased production of lactate Reduced reliance on glycolytic systems Respiratory exchange ratio decreases due to: Increased utilization of free fatty acids Oxygen consumption (VO2) Unchanged (or slightly reduced) at submaximal intensities VO2max increases Limited by the ability of the cardiovascular system to deliver oxygen to active muscles . .

Changes in Lactate Threshold With Training

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Changes in Race Pace With Continued Training After VO2max Stops Increasing .

Increased Performance After VO2max Has Peaked . 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. . . .

Factors Affecting VO2max . Factors Affecting VO2max Level of conditioning: Initial state of conditioning will determine how much VO2max will increase (i.e., the higher the initial value, the smaller the expected increase) Heredity: Accounts for 25-50% of the variation in VO2max Sex: Women have lower VO2max compared to men Individual responsiveness: There are high responders and low responders to endurance training, which is a genetic phenomenon . . .

Comparisons of VO2max in Twins and Nontwin Brothers . Comparisons of VO2max in Twins and Nontwin Brothers Adapted, by permission, from C. Bouchard et al., 1986, “Aerobic performance in brothers, dizygotic and monozygotic twins,” Medicine and Science in Sports and Exercise 18: 639-646.

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Variations in the Percentage Increase in VO2max for Identical Twins . From D. Prud'homme et al., 1984, “Sensitivity of maximal aerobic power to training is genotype-dependent,” Medicine and Science in Sports and Exercise 16(5): 489-493. Copyright 1984 by American College of Sports Medicine. Adapted by permission.

. Variations in the Improvement in VO2max Following 20 Weeks of Endurance Training . Adapted, by permission, from C. Bouchard et al., 1999, “Familial aggregation of VO2max response to exercise training: Results from HERITAGE Family Study,” Journal of Applied Physiology 87: 1003-1008.

Cardiorespiratory Endurance and Performance It is the major defense against fatigue Should be the primary emphasis of training for health and fitness All athletes can benefit from maximizing their endurance

Adaptations to Aerobic Training Key Points Although VO2max has an upper limit, endurance performance can continue to improve An individual’s genetic makeup predetermines a range for his or her VO2max and accounts for 25-50% of the variance in VO2max Heredity largely explains an individual’s response to training Highly conditioned female endurance athletes have VO2max values about 10% lower than their male counterparts All athletes can benefit from maximizing their cardiorespiratory endurance . . . .

Summary of Cardiovascular Adaptation to Chronic Endurance Training Adapted, by permission, from Donna H. Korzick, Pennsylvania State University, 2006.

Muscle Adaptations to Anaerobic Training Increased muscle fiber recruitment Increased cross-sectional area of type IIa and type IIx muscle fibers

Energy System Adaptations to Anaerobic Training Increased ATP-PCr system enzyme activity Increased activity of several key glycolytic enzymes No effect on oxidative enzyme activity

Changes in Creatine Kinase (CK) and Myokinase (MK) Activities With Anaerobic Training

Performance in a 60 s Sprint Bout After Anaerobic Training

Anaerobic Training Key Points Anaerobic training bouts improve both anaerobic power and anaerobic capacity Increased performance with anaerobic training is attributed to strength gains Increases ATP-PCr and glycolytic enzymes

Specificity of Training and Cross-Training To maximize cardiorespiratory gains from training, the training should be specific to the type of activity that the athlete usually performs Cross-training is training for more than one sport at a time Gains in muscular strength and power are less when strength training is combined with endurance training

. VO2max Values During Uphill Treadmill Running vs. Sport-Specific Activities in Selected Groups of Athletes Adapted, by permission, from S.B. Strømme, F. Ingjer, and H.D. Meen, 1977, “Assessment of maximal aerobic power in specifically trained athletes,” Journal of Applied Physiology 42: 833-837.