I have to disagree with the one review listed here. I found the book to be quite informative. It discusses the phyisiological benefits of jumping -- including muscle toning, better posture, lymphatic cleansing, stress reduction, anti-aging, increased balance and coordination, improvements in vision -- and more. I have no idea how sound the medical information is in the book, and actually, I'm not reading it for that content. Intuitively, I sense the it's got to be healthy no matter what the medical details are. There are a total of 33 illustrated exercises graded from basic to advanced. I'm 51 and I'm doing the exercises in the book. My muscles are toning nicely and there's no doubt in my mind that my posture is improving and I'm healthier all around. The book is a pretty good guide in getting started gently. The advanced exercises are a real workout. I recommend the book!