Sam has entered into an exercise physiology study. As part of the study, the res

Question

Sam has entered into an exercise physiology study. As part of the study, the researchers want to measure cardiac output at different workloads. One of these activities is a treadmill run. Sam has been running on the treadmill for several minutes and one of the researchers tells him that his end diastolic volume is high, making his stroke volume high. When Sam asks how this happens, the researcher tells him that it has a lot to do with venous return. If Sam’s heart rate has not changed since the beginning of the exercise, describe how venous return increased. Furthermore, explain how Sam’s mean arterial pressure hasn’t changed even though his stroke volume has.

Explanation / Answer

Treadmill exercise significantly increased lung ventilation, gular pumping, intra-abdominal pressure, mean arterial blood pressure and venous return (blood flow in the post caval vein). However, venous return declines at high levels of activity, and mean arterial pressure and venous return did not attain peak values until the recovery period.

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