Are they starting to weigh? wait put the last one on too.
Now I want you to lift the last two, lift not by much and then let it fall on the others.
Done? sure it did not hurt? Again.
hahaha
Now do it again but get up two books at your chin height and drop them.
Better? get up three now ... you know how ahaha ends
Take again only the last two, raise it above your head, and then ... let it fall.