Don't overtrain the abdominals
Below is a great article on how training the abdominals can make an existing back condition worse. A lot of Pilates instructors work a lot on flexion to "strengthen the core" but too much flexion and not enough work in other planes can actually weaken core stability. The article also a refers to the landmark Australian physiotherapy lab study that many point to to justify core exercise. The well-known study concluded that those with back pain could find some relief my changing their stabilizing strategy. The study did not however say that those who have a successful stabilization strategy can avoid back pain by strengthening their core. Take a look at the article.
http://well.blogs.nytimes.com/2009/06/17/core-myths/?partner=rss&emc=rss
