In the original edition of Strong Women Stay Young, there was an exercise called "hip extension". In the revised edition, this exercise has been usurped by an exercise called "standing leg curl". Why was the "hip extension" done away with? I've been comfortable doing this exercise. Is it okay if I use that instead of the "standing leg curl"?

The hip extension exercise in the original book is not in the revised edition because I received several letters indicating that it was aggravating some people's lower back. 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. If you are still doing the hip extension exercise and have found it useful, it is fine to continue doing it.