Chung et al (2013 Journal of Sports Science and Medicine) found exercises using a ball were more effective at increasing multifidus cross-sectional than the same exercises without a ball.
The programme comprised a supine bridge, horse stance/ bird dog variant, plank and a lower abdominal exercise. Each exercise was done 10 times for 5 sets with 15 secs rest sets. Given the popularity of attacking core stability programmes, it is interesting to note this protocol produced significant improvements in pain and function.
Courtesy of Kieran Macphail, Physiotherapist.