Continuing (2+ years) of aerial circus, which kinda counts as lifting heavy things.

Definitely counts! It is a strength-type activity! Also that sounds terrifying and amazing.

I also like doing this thing from plank where I slide my feet up into a tuck, and then back (requires a slippery floor and socks or a piece of cloth for the feet to slide with).

You can do this with rings or a TRX-type system too, with your feet in the rings/footloops.