My three year old just got a new mattress and box spring and as we were taking the old ones out of the house to the garage the kids asked if they could jump on them. For once, my husband and I gave the okay to jumping on the bed, not realizing that we had created a make-shift trampoline in the back yard.
The kids get sweaty pretty fast from jumping and have to take water breaks. I've taken a few bounces myself and it's pretty fun. We start at the back steps, jump on the mattress, take a few high hops, and do a twist and dismount onto the grass combining gymnastics and half-pipe moves (not really, but we try).