Adaptations to Aerobic Endurance Training Programs

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Adaptations to Aerobic Endurance Training Programs
chapter 6
Adaptationsto Aerobic EnduranceTraining
Programs
Ann Swank, PhD, CSCS, FACSM
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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 physio-logical
  characteristics of the cardiovascular,
  respiratory, nervous, muscular, bone and
  connective tissue, and endocrine systems.
• (continued)

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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.

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Section Outline

• Acute Responses to Aerobic Exercise
• Cardiovascular Responses
• 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

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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.

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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.

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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.

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Key Term

• maximal oxygen uptake The greatest amount of
  oxygen that can be used at the cellular level for
  the entire body.

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Key Term

• resting oxygen uptake Estimated at 3.5 mlof
  oxygen per kilogram of body weight per minute (ml
  kg1 min1) this value is defined as 1
  metabolic equivalent (MET).

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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.

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Blood Pressures in the Circulatory System

• Figure 6.1 (next slide)
• Blood pressures in the various portions of the
  circulatory system

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Figure 6.1
Reprinted, by permission, from Guyton, 1991.
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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.

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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.

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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.

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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
  roomair that mixes with alveolar air, about 150
  ml of airin the larger passages (anatomical dead
  space),and a small portion of air distributed to
  either poorly ventilated or incompletely filled
  alveoli (physiological dead space).

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Figure 6.2
Reprinted, by permission, from McArdle, Katch,
and Katch, 1996.
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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.

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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.

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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.

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Figure 6.3
Reprinted, by permission, from Fox, Bowers, and
Foss, 1993.
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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.

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Section Outline

• Chronic Adaptations to Aerobic Exercise
• Cardiovascular Adaptations
• Respiratory Adaptations
• Neural Adaptations
• Muscular Adaptations
• Bone and Connective Tissue Adaptations
• Endocrine Adaptations

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Table 6.1
(continued)
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Table 6.1 (continued)
(continued)
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Chronic Adaptations to Aerobic Exercise

• Cardiovascular Adaptations
• Aerobic endurance training requires proper
  progression, variation, specificity, and overload
  if physiological adaptations are to take place.

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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.

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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.

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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.

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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.

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Section Outline

• Designing Aerobic Endurance Programs for
  Optimizing Adaptations

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Key Points

• One of the most commonly measured adaptations to
  aerobic endurance trainingis 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 main-taining
  aerobic power.

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Key Point

• Aerobic endurance training results in re-duced
  body fat, increased maximal oxygen uptake,
  increased respiratory capacity, lower blood
  lactate concentrations, increased mitochondrial
  and capillary densities, and improved enzyme
  activity.

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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

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Table 6.2
(continued)
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Table 6.2 (continued)
(continued)
(continued)
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Table 6.2 (continued)
(continued)
(continued)
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Section Outline

• External Influences on the Cardiorespiratory
  Response
• Altitude
• Hyperoxic Breathing
• Smoking
• Blood Doping

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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.

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Table 6.3
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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.

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Section Outline

• Individual Factors Influencing Adaptations to
  Aerobic Endurance Training
• Genetic Potential
• Age and Sex
• Overtraining
• Cardiovascular Responses
• Biochemical Responses
• Endocrine Responses
• Detraining

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Individual Factors Influencing Adaptations to
Aerobic Endurance Training

• Genetic Potential
• The upper limit of an individuals 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.

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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-to-cortisol ratio, decreased
  secretion of GH, and changes in catecholamine
  levels.

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Key Point

• Overtraining can lead to dramatic performance
  decreases in athletes of all training levels and
  is caused by mistakesin the design of the
  training program.

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Individual Factors Influencing Adaptations to
Aerobic Endurance Training

• What Are the Markers of Aerobic Overtraining?
• 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)

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Individual Factors Influencing Adaptations to
Aerobic Endurance Training

• What Are the Markers of Aerobic Overtraining?
  (continued)
• 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)

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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
  hormonebinding globulin
• Decreased sympathetic tone (decreased nocturnal
  and resting catecholamines)
• Increased sympathetic stress response

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Individual Factors Influencing Adaptations to
Aerobic Endurance Training

• Detraining
• If inactivity, rather than proper recovery,
  follows exercise, an athlete loses training
  adaptations.