Standing still for long periods of time decrease cardiacoutput because:
A) venous return decreases due to lack of skeletal msusclepumping of veins, so stroke volume drops.
B) too much lactic acide is produced so blood vessels dilateand blood pressure drops
C) parasympathetic activity causes vasodilation
or
D) Heart rate falls too low to maintain cardiac output withoutpropioceptive input to the cardiovascular center