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chapter
Adaptations
6
to Aerobic Endurance
Training Programs
Adaptations
to Aerobic Endurance
Training Programs
Ann Swank, PhD, CSCS, FACSM
Chapter Objectives
• Identify and describe acute responses of
the cardiovascular and respiratory systems
to aerobic exercise.
• Identify and describe the impact of chronic
aerobic endurance training on the physiological characteristics of the cardiovascular,
respiratory, nervous, muscular, bone and
connective tissue, and endocrine systems.
(continued)
Chapter Objectives (continued)
• Recognize the interaction between
designing aerobic endurance training
programs and optimizing physiological
responses of all body systems.
• Identify and describe external factors that
influence adaptations to acute and chronic
aerobic exercise.
• Recognize the causes, signs, symptoms,
and effects of overtraining and detraining.
Section Outline
• Acute Responses to Aerobic Exercise
– Cardiovascular Responses
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Cardiac Output
Stroke Volume
Heart Rate
Oxygen Uptake
Blood Pressure
Control of Local Circulation
– Respiratory Responses
• Gas Responses
• Blood Transport of Gases and Metabolic By-Products
Acute Responses to Aerobic Exercise
• Cardiovascular Responses
– Cardiac Output
• From rest to steady-state aerobic exercise, cardiac output
initially increases rapidly, then more gradually, and
subsequently reaches a plateau.
• With maximal exercise, cardiac output may increase to four
times the resting level.
Key Terms
.
• cardiac output (or Q): The amount of blood
pumped by the heart in liters per minute
(SV × HR).
• stroke volume: The quantity of blood ejected
with each beat.
Acute Responses to Aerobic Exercise
• Cardiovascular Responses
– Stroke Volume
• End-diastolic volume is significantly increased.
• At onset of exercise, sympathetic stimulation increases
stroke volume.
– Heart Rate
• Heart rate increases linearly with increases in intensity.
– Oxygen Uptake
• Oxygen uptake increases during an acute bout of aerobic
exercise and is directly related to the mass of exercising
muscle, metabolic efficiency, and exercise intensity.
Key Term
• maximal oxygen uptake: The greatest amount
of oxygen that can be used at the cellular level
for the entire body.
Key Term
• resting oxygen uptake: Estimated at 3.5 ml
of oxygen per kilogram of body weight per
minute (ml · kg–1 · min–1); this value is defined
as 1 metabolic equivalent (MET).
Acute Responses to Aerobic Exercise
• Cardiovascular Responses
– Blood Pressure
• Systolic blood pressure estimates the pressure exerted
against the arterial walls as blood is forcefully ejected
during ventricular contraction.
• Diastolic blood pressure is used to estimate the pressure
exerted against the arterial walls when no blood is being
forcefully ejected through the vessels.
Blood Pressures
in the Circulatory System
• Figure 6.1 (next slide)
– Blood pressures in the various portions of the
circulatory system
Figure 6.1
Reprinted, by permission, from Guyton, 1991.
Acute Responses to Aerobic Exercise
• Cardiovascular Responses
– Control of Local Circulation
• During aerobic exercise, blood flow to active muscles is
considerably increased by the dilation of local arterioles.
• At the same time, blood flow to other organ systems is
reduced by constriction of the arterioles.
Key Point
• Acute aerobic exercise results in increased
cardiac output, stroke volume, heart rate,
oxygen uptake, systolic blood pressure, and
blood flow to active muscles and a decrease
in diastolic blood pressure.
Acute Responses to Aerobic Exercise
• Respiratory Responses
– Aerobic exercise, as compared to other types of
exercise, provides for the greatest impact on both
oxygen uptake and carbon dioxide production.
Tidal Volume
• Figure 6.2 (next slide)
– The slide shows the distribution of tidal volume in a
healthy athlete at rest.
– The tidal volume comprises about 350 ml of room
air that mixes with alveolar air, about 150 ml of air
in the larger passages (anatomical dead space),
and a small portion of air distributed to either poorly
ventilated or incompletely filled alveoli (physiological
dead space).
Figure 6.2
Reprinted, by permission, from McArdle, Katch, and Katch, 1996.
Key Point
• During aerobic exercise, large amounts of
oxygen diffuse from the capillaries into the
tissues, increased levels of carbon dioxide
move from the blood into the alveoli, and
minute ventilation increases to maintain
appropriate alveolar concentrations of these
gases.
Acute Responses to Aerobic Exercise
• Respiratory Responses
– Gas Responses
• During high-intensity aerobic exercise, the pressure
gradients of oxygen and carbon dioxide cause the
movement of gases across cell membranes.
• The diffusing capacities of oxygen and carbon dioxide
increase dramatically with exercise, which facilitates their
exchange.
Pressure Gradients
• Figure 6.3 (next slide)
– The slide shows pressure gradients for gas transfer
in the body at rest.
– The pressures of oxygen (PO2) and carbon dioxide
(PCO2) in ambient air, tracheal air, and alveolar air
are shown.
– The gas pressures in venous and arterial blood and
muscle tissue are shown.
Figure 6.3
Reprinted, by permission, from Fox, Bowers, and Foss, 1993.
Acute Responses to Aerobic Exercise
• Respiratory Responses
– Blood Transport of Gases and Metabolic By-Products
• Most oxygen in blood is carried by hemoglobin.
• Most carbon dioxide removal is from its combination with
water and delivery to the lungs in the form of bicarbonate.
• During low- to moderate-intensity exercise, enough oxygen
is available that lactic acid does not accumulate because the
removal rate is greater than or equal to the production rate.
• The aerobic exercise level at which lactic acid (converted to
blood lactate at this point) begins to show an increase is
termed the onset of blood lactate accumulation, or OBLA.
Section Outline
• Chronic Adaptations to Aerobic Exercise
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Cardiovascular Adaptations
Respiratory Adaptations
Neural Adaptations
Muscular Adaptations
Bone and Connective Tissue Adaptations
Endocrine Adaptations
Table 6.1
(continued)
(continued)
Table 6.1 (continued)
Chronic Adaptations
to Aerobic Exercise
• Cardiovascular Adaptations
– Aerobic endurance training requires proper
progression, variation, specificity, and overload if
physiological adaptations are to take place.
Chronic Adaptations
to Aerobic Exercise
• Respiratory Adaptations
– Ventilatory adaptations are highly specific to
activities that involve the type of exercise used in
training.
– Training adaptations include increased tidal volume
and breathing frequency with maximal exercise.
• Neural Adaptations
– Efficiency is increased and fatigue of the contractile
mechanisms is delayed.
Chronic Adaptations
to Aerobic Exercise
• Muscular Adaptations
– One of the fundamental adaptive responses to
aerobic endurance training is an increase in the
aerobic capacity of the trained musculature.
– This adaptation allows the athlete to perform a given
absolute intensity of exercise with greater ease after
aerobic endurance training.
Chronic Adaptations
to Aerobic Exercise
• Bone and Connective Tissue Adaptations
– In mature adults, the extent to which tendons,
ligaments, and cartilage grow and become stronger
is proportional to the intensity of the exercise
stimulus, especially from weight-bearing activities.
Chronic Adaptations
to Aerobic Exercise
• Endocrine Adaptations
– Aerobic exercise leads to increases in hormonal
circulation and changes at the receptor level.
– High-intensity aerobic endurance training augments
the absolute secretion rates of many hormones in
response to maximal exercise.
– Trained athletes have blunted responses to
submaximal exercise.
Section Outline
• Designing Aerobic Endurance Programs for
Optimizing Adaptations
Key Points
• One of the most commonly measured
adaptations to aerobic endurance training
is an increase in maximal oxygen uptake
associated with an increase in maximal
cardiac output.
• The intensity of training is one of the most
important factors in improving and maintaining aerobic power.
Key Point
• Aerobic endurance training results in reduced body fat, increased maximal oxygen
uptake, increased respiratory capacity,
lower blood lactate concentrations,
increased mitochondrial and capillary
densities, and improved enzyme activity.
Physiological Variables
in Aerobic Endurance Training
• Table 6.2 (next slides)
– These subjects completed a short-term (three- to
six-month) aerobic endurance training program.
– BTPS = body temperature and pressure, saturated
Table 6.2
(continued)
(continued)
Table 6.2 (continued)
(continued)
(continued)
(continued)
Table 6.2 (continued)
Section Outline
• External Influences on the Cardiorespiratory
Response
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Altitude
Hyperoxic Breathing
Smoking
Blood Doping
External Influences on the
Cardiorespiratory Response
• Altitude
– Changes begin to occur at elevations greater than
3,900 feet (1,200 m):
• Increased pulmonary ventilation
• Increased cardiac output at rest and during submaximal
exercise due to increases in heart rate
– Values begin to return toward normal within two
weeks.
– Several chronic physiological and metabolic
adjustments occur during prolonged altitude
exposure.
Table 6.3
External Influences on the
Cardiorespiratory Response
• Hyperoxic Breathing
– Breathing oxygen-enriched gas mixtures during rest periods or
following exercise may positively affect exercise performance,
although the procedure remains controversial.
• Smoking
– Acute effects of tobacco smoking could impair exercise
performance.
• Blood Doping
– Artificially increasing red blood cell mass is unethical and
poses serious health risks, yet it can improve aerobic exercise
performance and may enhance tolerance to certain
environmental conditions.
Section Outline
• Individual Factors Influencing Adaptations
to Aerobic Endurance Training
– Genetic Potential
– Age and Sex
– Overtraining
• Cardiovascular Responses
• Biochemical Responses
• Endocrine Responses
– Detraining
Individual Factors Influencing Adaptations
to Aerobic Endurance Training
• Genetic Potential
– The upper limit of an individual’s genetic potential
dictates the absolute magnitude of the training
adaptation.
• Age and Sex
– Maximal aerobic power decreases with age in
adults.
– Aerobic power values of women range from 73% to
85% of the values of men.
– The general physiological response to training is
similar in men and women.
Individual Factors Influencing Adaptations
to Aerobic Endurance Training
• Overtraining
– Cardiovascular Responses
• Greater volumes of training affect heart rate.
– Biochemical Responses
• High training volume results in increased levels of creatine
kinase, indicating muscle damage.
• Muscle glycogen decreases with prolonged periods of
overtraining.
– Endocrine Responses
• Overtraining may result in a decreased testosterone-tocortisol ratio, decreased secretion of GH, and changes in
catecholamine levels.
Key Point
• Overtraining can lead to dramatic
performance decreases in athletes of all
training levels and is caused by mistakes
in the design of the training program.
Individual Factors Influencing Adaptations
to Aerobic Endurance Training
• What Are the Markers of Aerobic
Overtraining?
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Decreased performance
Decreased percentage of body fat
Decreased maximal oxygen uptake
Altered blood pressure
Increased muscle soreness
Decreased muscle glycogen
Altered resting heart rate
(continued)
Individual Factors Influencing Adaptations
to Aerobic Endurance Training
• What Are the Markers of Aerobic
Overtraining? (continued)
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Increased submaximal exercise heart rate
Decreased lactate
Increased creatine kinase
Altered cortisol concentration
Decreased total testosterone concentration
Decreased ratio of total testosterone to cortisol
(continued)
Individual Factors Influencing Adaptations
to Aerobic Endurance Training
• What Are the Markers of Aerobic
Overtraining? (continued)
– Decreased ratio of free testosterone to cortisol
– Decreased ratio of total testosterone to sex
hormone–binding globulin
– Decreased sympathetic tone (decreased nocturnal
and resting catecholamines)
– Increased sympathetic stress response
Individual Factors Influencing Adaptations
to Aerobic Endurance Training
• Detraining
– If inactivity, rather than proper recovery, follows
exercise, an athlete loses training adaptations.