If your dog cannot maintain correct posture standing on stable ground, then having them wobble around on an inflatable prop such as a fit bone or a peanut is just random activity that can do more harm than good.
Discover the difference in an effective conditioning program with purpose, versus random activity.

If you want to condition your dog, you need instruction from a credentialed canine strength and conditioning trainer, preferably through a veterinary college accredited program such as CSCC (NC State University) or CCFT (Univ. Tennessee), or one of the other professionally taught programs such as CPCFT.

What about authorized AKC Fit Dog classes? This might be a good place to start IF your instructor is additionally/otherwise credentialed and can expand upon the basics offered in the AKC program. Just know that there is much more to properly design and implement a canine conditioning program, so be sure your instructor has additional training and knowledge to do so.

As CSCC Certified Canine Strength and Conditioning Coach and AKC Level 3 Fit Dog Instructor, I provide instruction in the basics all the way to complete conditioning programs designed to meet individual needs for sports or just better quality of life.

Know the difference, know what you are getting in a canine fitness trainer for your dog!