Chapter 6: Adaptations to Aerobic Endurance Training Programs Flashcards
Primary functions of the cardiovascular system during aerobic exercise
- Deliver oxygen and other nutrients to the working muscles
- Remove metabolites and waste products
Cardiac Output
- The amount of blood pumped by the heart in linters per minute
- Determined by the product of stroke volume and heart rate
- Q = Stroke Volume x Heart Rate
Stroke Volume
Quantity of blood ejected with each heart beat
Heart Rate
The heart’s rate of pumping in beats per minute
Progression of cardiac output from rest to steady-state aerobic exercise
Initially increases rapidly, then more gradually, then reaches a plateau
Response of cardiac output to maximal aerobic exercise
Cardiac output may increase to 4x the resting level (5 L’min to a max of 20-22 L/min)
Response of stroke volume to aerobic exercise
- Increases at the onset of exercise
- Continues to rise until individual reaches ~40-50% of VO2max
- Plateaus at 40-50% of VO2max
Max stroke volume for sedentary and trained college-aged men/women
Men - 100-120 mL/beat (sedentary) - 150-160 mL/beat (after training) Women - ~25% less (sedentary) - 100-110 mL/beat (after training)
Physiological mechanisms that regulate stroke volume
- End-diastolic volume
- Hormone response (epinephrine and norepinephrine) which produces a more forceful ventricular contraction
End-diastolic Volume
The volume of blood available to be pumped by the left ventricle at the end of the filling phase (diastole)
Venous Return
The amount of blood returning to the heart
Factors that cause venous return to increase
- Vasoconstriction (induced via increased sympathetic nervous system activation)
- Skeletal muscle pump (muscular contractions combine with one-way venous valves to “push” more blood to the heart during exercise)
- Respiratory pump
Skeletal Muscle Pump
Muscular contractions combine with one-way venous valves to “push” more blood to the heart during exercise
Respiratory Pump
Increased respiratory frequency and tidal volume
Frank-Sterling Mechanism
A greater end-diastolic volume increases the contractile strength of the ventricles and thus increases stroke volume
Ejection Fraction
The fraction of the end-diastolic volume ejected from the heart
Response of heart rate to aerobic exercise
- A reflex or stimulation of the sympathetic nervous system results in an increase of heart rate
How does heart rate change as exercise intensity increases?
HR increases linearly with increases in intensity during aerobic exercise
Oxygen Uptake
The amount of oxygen consumed by the body’s tissues
What effect does aerobic exercise have on oxygen demand?
- Increases during an acute bout of aerobic exercise
- Directly related to the mass of exercising muscle, metabolic efficiency, and exercise intensity
Maximal Oxygen Uptake
Greatest amount of oxygen that can be used at the cellular level for the entire body
Metabolic Equivalent (MET)
- The estimated resting oxygen uptake is 3.5 ml/kg/min (1 MET)
Fick Equation
VO2 = Q x a-vO2 difference
Arteriovenous Oxygen Difference
- The difference in the oxygen content between arterial and venous blood
- VO2 = Q x a-vO2 difference
- VO2 = Heart rate x Stroke volume x a-vO2 difference
Systolic Blood Pressure
The pressure exerted against the arterial walls as blood is forcefully ejected during ventricular contraction
Systole
Ventricular contraction
Rate-Pressure Product
- AKA double product
- Heart Rate x Systolic blood pressure
- Can be used to describe the myocardial oxygen consumption (work) of the heart
Diastolic Blood Product
Estimate the pressure exerted against the arterial walls when no blood is being forcefully ejected through the vessels
Mean Arterial Pressure
- The average blood pressure throughout the cardiac cycle
- MAP = [(Systolic BP - Diastolic BP)/3] + Diastolic BP
Normal BP Ranges
Systolic : 110-139 (220-260 during max exercise)
Diastolic: 60-89
What is the main mechanism for regulating blood flow?
Vasoconstriction and vasodilation of the blood vessels
Vasoconstriction
The constriction of blood vessels, which increases blood pressure.
Vasodilation
The dilatation of blood vessels, which decreases blood pressure.
Minute Ventilation
The volume of air breathed per minute
What factors increase minute ventilation during exercise?
- Increased breath depth
- Increased breathing frequency
Tidal Volume
The amount of air inhaled and exhaled with each breath
Ventilatory Equivalent
The ratio of minute ventilation to oxygen uptake
During low- to moderate-intensity aerobic exercise, what causes the increase in ventilation?
Increased tidal volume
During high-intensity exercise, what causes the increase in ventilation?
Increased breathing frequency
Alveoli
The functional unit of the pulmonary system where gas exchange occurs
Anatomical Dead Space
- Areas of the respiratory passages which does not function for gas exchange
- Nose, mouth, trachea, bronchi, and bronchioles
Physiological Dead Space
Alveoli in which poor blood flow, poor ventilation, or other problems with the alveolar surface impair gas exchange
Diffusion
- The movement of oxygen and carbon dioxide across a cell membrane
- A function of the concentration of each gas and the resulting partial pressure exerted by the molecular motion of each gas
Adaptations to chronic aerobic exercise
- Increased max cardiac output
- Increased stroke volume
- Reduced HR at rest and during submax exercise
- Increased muscle fiber capillary density
Most significant change in cardiovascular function with long-term aerobic training
Maximal cardiac output, resulting primarily from improved stroke volume
Myoglobin
- A protein that transports oxygen within a muscle cell
- Increases as a result of aerobic training
Mitochondria
Organelles in cells that are responsible for aerobically producing ATP
Which aerobic programs are most successful in improving bone mass?
More intense physical activities such as running and high-intensity aerobics
External and individual factors influencing adaptation to aerobic training
- Altitude
- Hyperoxic breathing
- Smoking
- Blood doping
- Genetic potential
- Age and Sex
Acute adjustments to altitude hypoxia
- Pulmonary: hyperventilation
- Acid-base: body fluids become more alkaline due to reduction in CO2 with hyperventilation
- Cardiovascular: CO increases at rest and submax exercise; submax HR increases; Stroke volume, max HR, and max CO remains the same/slightly lower
Chronic adjustments to altitude hypoxia
- Pulmonary: Increase in ventilation rate stabilizers
- Acid-base: Excretion of HCO3- by the kidneys with concomitant reduction in alkaline reserve
- Cardiovascular: Continued elevation in submax HR; decreased stroke volume; lower max HR and CO
- Hematologic: Increased red cell production, viscosity, hematocrit; decreased plasma volume
Hyperventilation
An increase in pulmonary ventilation
Hyperoxic Breathing
Breathing oxygen-enriched gas mixtures
Blood doping
The practice of artificially increasing red blood cell mass
Overtraining
- A process that can result in overreaching in the short term (functional overreaching) or extreme overreaching (nonfunctional overreaching) or overtraining syndrome (OTS) in the long term
- Occurs when there is not adequate recovery
Cardiovascular responses to overtraining
- Resting HR can be either decreased or increased in association with OTS
- HR variability can decrease with onset of OTS (indicates reduced parasympathetic input or excessive sympathetic stimulation)
Biochemical responses to overtraining
- Increased levels of creatine kinase (indicating muscle damage)
- Lactate concentrations either decrease or stay the same
- Muscle glycogen decreases
Endocrine responses to overtraining
- Total testosterone decreases after an initial increase in response to the exercise stimuli
- Decreased pituitary secretion of growth hormone
Strategies for avoiding overtraining syndrome
- Good nutrition
- Sufficient sleep and recovery time
Detraining
The partial or complete loss of training-induced adaptations in response to an insufficient training stimulus
Tapering
- The planned reduction of volume (usually in duration and frequency, not intensity) that occurs before an athletic competition or a planned recovery microcycle
- Designed to enhance performance and adaptations
- Aerobic endurance adaptations are most sensitive to periods of inactivity due to their enzymatic basis
