Today’s exercise to increase the supporting strength and train the abdominals is just perfect for in between: In the waiting room of the doctor, on a bench in a park or also on a bus stop.
I sit down straight with the hands on the side of my bottom. The fingertips look forward. Then I lift my bottom and the bended legs up in the air and start extending my legs forward and bending them back again a few times. That’s quit exhausting.
Good luck with it!