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the pressure against which the heart must pump blood, determined by the peripheral resistance in the large arteries
afterload
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the point at which the metabolic demands of exercise can no longer be met by available aerobic sources and at which an increase in anaerobic metabolism occurs, reflected by an increase in blood lactate concentration.
anaerobic threshold
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an increase in heart rate during exercise to compensate for a decrease in stroke volume. this compensation helps maintain a constant cardiac output.
cardiovascular drift
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information originating in the brain that is transmitted to the cardiovascular, muscular, or pulmonary systems
central command
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labored or difficult breathing
dyspnea
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a decline in arterial PO2 and arterial oxygen saturation during maximal or near-maximal exercise
exercise induced arterial hypoxemia (EIAH)
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the mechanism by which an increased amount of blood in the ventricle causes a stronger ventricular contraction to increase the amount of blood ejected
Frank-Starling mechanism
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a relative (not absolute) increase in the cellular content per unit of blood volume, resulting from a reduction in plasma volume
hemoconcentration
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a breathing rate or tidal volume greater than necessary for normal function
hyperventilation
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the maximal capacity to move air into and out of the lungs, usually measured for 12s and extrapolated to a per-minute value
maximal voluntary ventilation
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the highest heart rate value attainable during an all-out effort to the point of exhaustion
maximum heart rate (HR max)
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the degree to which the myocardium is stretched before it contracts, determined by factors such as central blood volume
preload
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the heart rate at rest, averaging 60-80 beats/min
resting heart rate (RHR)
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a heart rate that is maintained constant at submaximal levels of exercise when the rate of work is held constant
steady state heart rate
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the resistance to the flow of blood through the entire systemic circulation
total peripheral resistance (TPR)
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the process of holding the breath and attempting to compress the contents of the abdominal and thoracic cavities, causing increased intra-adominal and intrathoracic pressure
Valsalva Maneuver
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the ratio of the volume of air ventilated (Ve) to the amount of carbon dioxide produced (VCO2)
ventilatory equivalent for carbon dioxide (Ve/VCO2)
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the point at which ventilation increases disproportionately compared with oxygen consumption
ventilatory threshold (same as ventilatory breakpoint)
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