dr.mum
Forum Senior
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Preload is the load on a muscle in a relaxed state, prior to contraction. Afterload is the load the muscle is working against or trying to move during stimulation.
My Q is:
If a 100 g ball is suspended from a muscle, the 100 g should be preload. At the same time, there will be a 100 g passive tension. Then if the brain says, OK, muscle, lift the ball. Then the preload is becoming afterload? Passive tension = Afterload? No active tension is needed?
Thanks
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| muzammil
Forum Guru
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Posts: 655
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i think this 100 gm weight thing they use to help student understand the preload. in human body live muscles are prestretch to certain lenthgs this is preload and the weight that we move or try to move is after load.
in case of cardiac muscles the preload is edv and after load is pressure or resistence against which it is pumping blood.
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| MD_toronto
Forum Junior
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Posts: 27
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dear dr mum,
If the preload = afterload, then you can't move the load at all. Its will remain stationary according to your explaination.
to left 100g wieght you need to apply force greater than 100g. So, prestreched done by preload helps in making more cross-bridges in the muscles which helps to increase the force of contraction i.e. more than 100g. so, u do need preload to contribute force to afterload(after load is force generated during contraction) in order to left the weight.
i hope it make sense.
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| Ig F
Forum Elite
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