A 24-year-old professional athlete is advised to train in the mountains to enhance his performance. After 5 months of training at an altitude of 1.5 km (5,000 feet), he is able to increase his running pace while competing at sea-level venues. Which of the following changes would produce the same effect on the oxygen-hemoglobin dissociation curve as this athlete's training did?
ADecreased 2,3-bisphosphoglycerate
BIncreased carbon monoxide inhalation
CDecreased temperature
DDecreased pH
EIncreased partial pressure of oxygen
During exercise, what is the primary mechanism for increased oxygen delivery to active muscles?
ADecreased blood viscosity
BIncreased cardiac output
CIncreased hemoglobin affinity
DEnhanced oxygen diffusion
A 60-year-old male engineer who complains of shortness of breath when walking a few blocks undergoes a cardiac stress test because of concern for coronary artery disease. During the test he asks his cardiologist about what variables are usually used to quantify the functioning of the heart. He learns that one of these variables is stroke volume. Which of the following scenarios would be most likely to lead to a decrease in stroke volume?
AAnxiety
BHeart failure
CExercise
DPregnancy
EDigitalis
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