personal training for middle aged women

I have a degree in physical education that mostly covered coaching and teaching at a high school level. Currently I'm a personal trainer at a local gym. I typically train middle aged women and I see them once a week. Depending on their schedule, they may work-out a two or three more times during the week, but most of them just work-out with me 1x per week. They're goals are typically to loose weight or to stay healthy.

Most of my experience and training and most of the information that I have found is for athletes looking to achieve their personal best. I understand the principles of training and fitness and I know that really what these ladies need is more than one work-out/week and some serious cardio, but can any one recommend a not-so-intense personal training book?