mani
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preload increases only with heavy exercise. but my query is that even mild and moderate exercise will lead to vasodilation, dec TPR and hence should increase venous return and preload. any explanation?? (reference kaplan physio page 200)
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| ksc
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Exercise produces an increase in volume work of the heart that is mainly carried out by an increase in heart rate rather than a increase in stroke volume.
In light and moderate exercise there may be no increase in preload. Preload does increase in heavy exercise.
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| mjl1717
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I agree with ksc's 2nd sentence but I would not discount SV because it does increase in mild and moderate exercise maybe not to the same degree as HR but it has to increase.
Also pulse pressure will increase due to increased stroke volume.
{Dont want to sound redundant but these are important concepts for us.}
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| hiwa
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Mani
I am not sure if the preload is increased in heavy exercise, because best measure for preload is EDV and EDP,
In heavy exersice there is rapid HR (>140/min)which doesnt let proper ventricular filling and hence decreased EDV, (and dec strock volume),
while in mild to moderate exercise there is harmony between venouse return,proper ventricular filling , inc cardiac contractility, and therefore increased EDP&EDV---->inc preload.
another way to interpret it is, in mild to moderate exercise there is inceased strock volume- best factor to increase COP is inc EDV,EDP means(preload)
while in heavy exercise decrease strock volume so there should be decreased EDV and EDP means preload
provided that vascular tone in both senarios is constant because dilate in both types of exercise
please correct me if I am wrong
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| mani
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hiwa, how would u explain that sentence of kaplan that i have quoted?
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| hiwa
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Actually I dont know how to interprete it, but since it is mentioned in Kaplan there should be another explanation for it which I dont know sorry
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