I don't know if this is even true but i supose it could be:
But I heard that even for some walking animals, those exercise ballsare actually a frightening experience. Prey animals like rodents[lagamorphs too I suppose] are reluctant to go anywhere that they don'thave at least 2 ways out which is why, when you give many animals acardboard box etc, they will chew a hole in the back corner so thatthey have an 'emergency exit'. I guess it's an instinct thing - frombeing in burrows, warrens etc in case a predator gets into the burrow.
If this is the case, then the exercise ball is a stressful experienceand it could be that they are not exercising they are merely trying toescape but the ball perpetually turns until we let them out - I wasconsidering getting one for my chinchillas until I read this.
Having said this, they are widely accepted for hamsters etc.....andmany people say that they 'offer' the ball at the cage door and thehamster, gerbil or whatever just jumps in so I guess they must like it