Bats usually hang around upside down when they sleep. Today I will imitate them but I will get no sleep but train my abdominals in that position.
Therefore I hang with my knees on a bar – it could also be a strong branch – and let my body dangle down. Now I tense my abdominals and lift my torso up as much as I can to the knees and then I lower it back down slowly and carefully. Thereby I avoid swinging. To get back on the ground I grab the bar or the branch with my hands, release my knees and lower my feet down forward through my knees.