Eli5 why someone is heavier when they are limp versus when they have muscle tension

Question

Eli5 why someone is heavier when they are limp versus when they have muscle tension

In: 21

Answer 1

It’s not that they are heavier, just more difficult to carry when they’re limp. Imagine trying to carry a plastic bag with 20kg of water in compared to 20kg of water in a jerry can. The water in the plastic bag will move around and the bag will change shape so you will need to use some of your strength just keep it steady whereas in the jerry can the shape stays constant and you can use all your strength just to lift
it.