Something newer to me is the utilization of medicine balls during sessions.
(@ Leow’s Hotel)
On the Facebook Page, you’ll see researched methods to work your abdomen. They include reaching with wrist weights on or dumbbells in your hands. The illustration cites doing it while standing.
Thinking about it, If you can do that WHILE STANDING without a walker more power to ya. If you’re more comfortable sitting with your knees bent, try something. Grab a medicine ball (I started AND finished with a 6 lb. ball) and just extend your arms. With both hands firmly grasping the ball continue to lift the ball up, down, over your head, towards the floor and side to side.
You should notice your back muscles starting to fatigue and grow sore. The muscles in your back are crucial for standing straight and holding yourself erect.
LIVESTRONG ARTICLE on specific muscles used to sit and stand.
AZCentral ARTICLE on healthy posture.
SportsMD ARTICLE on back strain.