Why was the hip extension exercise omitted from the new edition to Strong Women Stay Young?

I removed the hip extension exercise (from the original Strong Women Stay Young) in the revised edition because I received a few letters indicating that it was aggravating some people's lower backs. If you are doing the chair stand correctly (which is still in the book), you are strengthening many of the same muscle groups that were trained in the hip extension. The hip extension can be a difficult exercise to do properly, and I felt the standing leg curl was a safer choice for the program-and safety is a priority. In some cases, I need to have several years of experience with an exercise before I can be sure it is working the way I want it to. If you are still doing the hip extension exercise and have found it useful, it is fine to continue doing it. If you are ready for a change, consider doing the standing leg curl.