The arterial-mixed venous oxygen difference increases as a function of exercise intensity. does not change during exercise. decreases as the exercise intensity increases. plateaus after about 40% to 60% VO2 max.

Exercise is associated with alterations to many basic physiological processes, including changes in metabolism and the cardiovascular system.  As the intensity of exercise rises, both the cardiac output and oxygen consumption increase, as shown in Figure 1.Figure 1  Changes in cardiac output and oxygen consumption in response to various levels of exerciseThe cardiac output CO represents the volume of blood pumped by the heart in 1 minute.  The CO is calculated from the heart rate HR and stroke volume SV using the equationCO = HR ∙ SVEquation 1Experimental data has shown that the HR increases linearly with the exercise output Eout, leading to the relationshipHR = 0.65 ∙ Eout + 75Equation 2The metabolism of nutrients consumes oxygen and generates carbon dioxide as a waste product.  The amount of carbon dioxide generated depends on the type of macronutrient that is consumed.  For example, when carbohydrates are metabolized, every liter of oxygen consumed causes the generation of 1.0 liter of carbon dioxide.  Alternatively, the metabolism of fats leads to 0.7 liters of carbon dioxide per liter of oxygen, and the metabolism of proteins generates 0.8 liters of carbon dioxide for each liter of oxygen. Question 56While exercising on a treadmill, a person has a cardiac output of 15 L/min and produces carbon dioxide at 0.091 mol/min.  What is their ratio of metabolizing carbohydrates to fats during the exercise?  (Assume all gasses are ideal and are at STP.)A.1:2B.1:1C.1:0D.2:1Submit

An increase in venous return _______.Question 8Select one:A.results in decreased preloadB.occurs with severe blood lossC.decreases EDVD.occurs during exercise

The initial increase in heart rate at the onset of incremental exercise is due to:Group of answer choicesincreased plasma adrenalinereduced vagal activityincreased venous return due to activation of the muscle pump

The primary determinant of oxygen uptake during exercise is the:Group of answer choicesExercise power outputExercise durationRelative mix of CHO and fat

The increase in cardiac output that occurs during exercise is due to_________