I believe you are referring to spondylolisthesis. Does your client have any symptoms? There are 4 types of spondylolisthesis although for your purposes that is probably irrelevant. Sometimes young atheletes develop this condition from overuse and overtraining in sports where the back is in extension, such as gymnastics or diving. Sometimes they don't realize they are developing a problem until later on in their adult lives. In older adults, degenerative spondy is more common.
It is also graded from I to IV with each nuraber representing a 25% slippage of the top vertebra over the one beneath it. Grade I spondy is a measurement of 1 to 25 %; Grade II is from 26 to 50%, etc. If her grade is higher than that, I doubt she is in the gym trying to work out.
I would suggest you read up on the condition before you start working with your client. Her back could be unstable and you will need to be careful working with her. Avoid any activity that puts the back in extension. Twisting activities should also be avoided. Even swimming is problematic, except for the sidestroke. Certain yoga poses would be very bad.
I found the most useful thing I learned was working muscles in isolation, and working very small. Sometimes I would do an exercise and I would only be lifting something a matter of inches -- no big movements at all.
One exercise I recall always being given was what I think is universally called "marching." Also you could work on strengthening the pelvic floor.
Hope this helps. Proceed carefully!!
