10

Adaptations to Aerobic and Anaerobic Training

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Aerobic vs. Anaerobic Training

Aerobic (endurance) training leads to• improved blood flow, and• increased capacity of muscle fibers to generate

ATP.

Anaerobic training leads to• increased muscular strength, and• increased tolerance for acid–base imbalances

during highly intense effort.

Adaptations to Aerobic Training

• Improved submaximal aerobic endurance and VO2max

• Muscular changes in fiber size, blood and oxygen supply, and efficiency of functioning

• Improved efficiency of energy production

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Endurance Training

Muscular Endurance• 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

• Related to muscular strength and anaerobic development

Cardiorespiratory Endurance• Ability of the whole body to sustain prolonged,

rhythmic exercise• Related to development of the cardiovascular and

respiratory (aerobic) system

Evaluating Cardiorespiratory Endurance

VO2max

• Highest rate of oxygen consumption attainable during maximal exercise

• Can be increased with endurance training

Oxygen Transport System• Components of the cardiorespiratory system that

transport O2 to and from active tissues• Evaluated with the Fick equation:

VO2 = SV HR a-vO2 diff• Can transport O2 more efficiently with adaptations

that occur with endurance training

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Changes in VO2max With 12 Months of Endurance Training

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Parameters Affected by 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

Key Points

Heart Size Adaptations• The left ventricle changes the most in response to

endurance training.• The internal dimensions of the left ventricle

increase mostly due to an increase in ventricular filling.

• The wall thickness of the left ventricle increases, making the potential contraction of the left ventricle more forceful.

Changes in Stroke Volume With Endurance Training

Key Points

Stroke Volume Adaptations• 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, contribute to increased SV.

• The increased size of the heart allows the left ventricle to stretch more and fill with more blood.

Heart Rate During Exercise

Submaximal• Decreases proportionately with the amount of

training completed• May decrease by 20 to 40 beats per min after 6

months of moderate trainingMaximal• Remains unchanged or decreases slightly• Thought to decrease to allow for optimal stroke

volume and maximize cardiac output

Resting Heart Rate

• Decreases with endurance training due to more blood returning to heart

• In sedentary individuals can decrease by 1 beat per min per week during initial training

• Highly trained athletes may have resting heart rates of 40 beats per min or less

Changes in Heart Rate With Endurance Training

Which Comes First?

Does increased stroke volume allow a decreased heart rate, or does decreased heart rate allow an increased stroke volume?

Heart Rate Recovery Period

• It is the time after exercise that it takes your heart to return to its resting rate.

• With training, heart rate returns to resting level more quickly after exercise.

• Has been used as an index of cardiorespiratory fitness.• Conditions such as altitude or heat can affect it.• Should not be used to compare individuals to one

another.

Changes in Heart Rate Recovery With Endurance Training

Did You Know . . . ?

Resistance training can lead to decreases in heart rate; however, these decreases are not as reliable or as large as those that occur as a result of endurance training.

Key Points

Cardiac Output Adaptations• Q either doesn’t change at rest or during

submaximal exercise, or it decreases slightly.• A slight change could be the result of an increase

in the a-vO2 difference due to greater oxygen extraction by the tissues.

• Q increases dramatically at maximal exertion due to the increase in maximal SV.

• 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.

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Changes in Cardiac Output With Endurance Training

Blood Flow Increases With Training

• Increased capillarization of trained muscles (higher capillary-to-fiber ratio)

• Greater opening of existing capillaries in trained muscles• More effective blood redistribution—blood goes where it is

needed• Increased blood volume

CAPILLARIZATION IN MUSCLES (>15%)

Untrained Trained

Key Points

Blood Pressure and Training• Blood pressure changes little during submaximal or

maximal exercise.• Resting blood pressure (both systolic and diastolic)

is lowered with endurance training in individuals with borderline or moderate hypertension.

• Blood pressure during lifting of heavy weights can cause increases in systolic and diastolic blood pressure, but resting blood pressure after weight lifting tends to remain unchanged or decrease.

(continued)

Key Points (continued)

Blood Volume and Training• Endurance training, especially intense training,

increases blood volume.• Blood volume increases due to an increase in plasma

volume (increases in ADH, aldosterone, and plasma proteins cause more fluid to be retained in the blood).

• Red blood cell volume increases, but increase in plasma volume is higher; thus, hematocrit decreases.

• Blood viscosity decreases, thus improving circulation and enhancing oxygen delivery.

• Changes in plasma volume are highly correlated with changes in SV and VO2max.

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Increases in Total Blood Volume and Plasma Volume With Endurance Training

Cardiovascular Adaptations to Training

• Left ventricle size and wall thickness increase• Stroke volume increases• Resting and submaximal heart rates decrease• Maximal heart rate stays the same or decreases• Blood volume increases• Blood pressure does not change or slightly decreases• Cardiac output is better distributed to active muscles

Key Points

Respiratory Adaptations to Training• Static lung volumes remain unchanged; tidal

volume, unchanged at rest and during submaximal exercise, increases with maximal exertion.

• Respiratory rate stays steady at rest, decreases with submaximal exercise, and can increase dramatically with maximal exercise after training.

• Pulmonary ventilation increases during maximal effort after training.

(continued)

Key Points (continued)

Respiratory Adaptations to Training• Pulmonary diffusion increases at maximal work

rates.• The a-vO2 difference increases with training due to

more oxygen being extracted by tissues.• The respiratory system is seldom a limiter of

endurance performance.• All the major adaptations of the respiratory system

to training are most apparent during maximal exercise.

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Muscular Adaptations

• Increased size of type I fibers• Increased number of capillaries supplying the muscles• Increased myoglobin content of muscle (allowing muscle to

have more oxygen)• Increased number, size, and oxidative enzyme activity of

mitochondria

Percentage of Change in the Activity of SDH and Maximal Oxygen Uptake

Leg Muscle 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 D.L. Costill et al., 1979, "Adaptations in skeletal muscle following strength training," Journal of Applied Physiology 46: 96-99.

Adaptations Affecting Energy Sources

• Trained muscles store more glycogen and triglycerides than untrained muscles.

• FFAs are better mobilized and more accessible to trained muscles.

• Muscles’ ability to oxidize fat increases with training.• Muscles’ reliance on fat stores first conserves

glycogen during prolonged exercise.

MITOCHONDRIA (A), GLYCOGEN (B), AND TRIGLYCERIDES (C)

Metabolic Adaptations to Training

Lactate threshold increases.Respiratory exchange ratio• decreases for submaximal efforts (greater use of

FFAs) and• increases at maximal levels.

Oxygen consumption (VO2) is• unaltered or slightly increased at rest,• unaltered or slightly decreased at submaximal

rates of work, and• increases at maximal exertion (VO2max) from 4% to

93% until limited by oxygen delivery.

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Changes in Lactate Threshold With Training

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.

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Factors Affecting VO2max

Level of conditioning—Max is reached within 8 to 18 months of heavy endurance training.

Heredity—Accounts for as much as half the variation in VO2max as well as an individual’s response to training.

Age—Decreases in VO2max with age might be a result of age-related decreases in activity levels.

Gender—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.

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Aerobic Endurance andPerformance

• It’s the major defense against fatigue, which limits optimal performance.

• Should be the primary emphasis of training for health and fitness.

• All athletes can benefit from maximizing their endurance.

Key Points

Adaptations to Aerobic Training• Aerobic training stresses type I fibers more than

type II fibers and causes type I fibers to increase in size (but not in percentage).

• Prolonged aerobic training may cause type IIb fibers to take on characteristics of type IIa fibers.

• The number of capillaries supplying each muscle fiber increases with training.

• Myoglobin (which stores oxygen) content increases in muscle about 75% to 80% with aerobic training.

(continued)

Key Points (continued)

Adaptations to Aerobic Training• Aerobic training increases the number and size of

mitochondria and the activities of oxidative enzymes.

• Endurance-trained muscle stores more glycogen and triglyceride than untrained muscle.

• Increased fat availability and capacity to oxidize fat lead to increased use of fat as an energy source, sparing glycogen.

Aerobic Training Considerations

Volume• Frequency of exercise bouts• Duration of each exercise bout

Intensity• Interval training• Continuous training

Training Volume

• Volume is the load of training in each training session and over a given period of time.

• Adaptations to given volumes vary from individual to individual.

• An ideal aerobic training volume appears to be equivalent to an energy expenditure of about 5,000 to 6,000 kcal per week.

• Athletes who train with progressively greater workloads eventually reach a maximal level of improvement beyond which additional training volume will not improve endurance or VO2max.

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Training Intensity

• Muscular adaptations are specific to the speed as well as duration of training.

• Athletes who incorporate high-intensity speed training show more performance improvements than athletes who perform only long, slow, low-intensity training.

• Aerobic intervals are repeated, fast-paced, brief exercise bouts followed by short rests.

• Continuous training involves one continuous, high-intensity exercise bout.

Change in Race Pace With Continued Training After Maximal Oxygen Uptake

Stops Increasing

Comparisons of VO2max of Twin 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 Undergoing the

Same Training Program

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.

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Variations in the Improvement in VO2max Following 20 Weeks of Endurance Training

by Family

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.

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Adaptations to Anaerobic Training

• Increased muscular strength• Slightly increased ATP-PCr and glycolytic enzymes• Improved mechanical efficiency• Increased muscle oxidative capacity (for sprints longer

than 30 s)• Increased muscle buffering capacity

Did You Know . . . ?

Performance improvements after anaerobic training (short, high-intensity training) appear to be related more to muscular strength gains than improvements in the anaerobic yield of ATP through the ATP-PCr and glycolytic systems.

Muscle Buffering Capacity

• Anaerobic training improves muscle buffering capacity, but aerobic training does little to increase the muscles’ capacity to tolerate sprint-type activities.

• Improved muscle buffering capacity allows sprint-trained athletes to generate energy for longer periods before fatigue limits the contractile process.

Selected Muscle Enzyme Activities(mmol · g-1 · min–1) for Untrained, Anaerobically

Trained, and Aerobically Trained Men

Aerobic enzymesOxidative systemSuccinate dehydrogenase 8.1 8.0 20.8Malate dehydrogenase 45.5 46.0 65.5Carnitine palmityl transferase 1.5 1.5 2.3

Anaerobic enzymesATP-PCr systemCreatine kinase 609.0 702.0 589.0Myokinase 309.0 350.0 297.0Glycolytic systemPhosphorylase 5.3 5.8 3.7Phosphofructokinase 19.9 29.2 18.9Lactate dehydrogenase 766.0 811.0 621.0

aDenotes a significant difference from the untrained value.

Anaerobically Aerobically Untrained trained trained

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a

a

a

Key Points

Adaptations to Aerobic Training• Ideal aerobic training volume is equivalent to a

caloric expenditure of 5,000 to 6,000 kcal per week.

• To perform at higher intensities, athletes must train at higher intensities.

• Aerobic interval training involves repeated bouts of short, high-intensity performance followed by short rest periods; continuous training—one prolonged, high-intensity bout—also helps generate aerobic benefits.

(continued)

Key Points (continued)

Adaptations to Anaerobic Training• Anaerobic training improves anaerobic

performance mostly as a result of strength gains.• Anaerobic training improves efficiency of

movement and thus reduces the energy expended for that movement.

• Bouts of anaerobic training lasting beyond 30 s rely on oxidation for energy; muscle aerobic capacity can be improved with this type of training.

• Anaerobic training increases muscle buffering capacity, thus delaying fatigue.

Methods of Monitoring Training Changes

• Repeated measurements of VO2max

• Lactate threshold tests• Comparing lactate values taken after steady-state

exercise at various times in the training period

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Changes in Creatine Kinase (CK) and Muscle Myokinase (MK) Activities

Performance in a 60 s Sprint Bout After Training With 6 s and 30 s Anaerobic

Bouts

VO2max Values During Uphill Treadmill Running Versus Sport-Specific Activities

Adapted, by permission, from S.B. Stromme, F. Ingjer, and H.D. Meen, 1977, "Assessment of maximal aerobic power in specifically trained athletes," Journal of Applied Physiology 42: 833-837.

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