I think the explanation in this video is ok but it might be interesting to mark out a space on the floor and pretend it is a bed of nails. Then get students to practice lying down on the “bed of nails” and standing up again. They fail if they double the pressure of their skin on the nails, e.g. sit in the bed, lie on their side, stand on the bed, put a hand on the nails that caries the weight of their body. Could be fun!