I am a 44-year-old woman with low back problems and recently bought your book on my mom's recommendation. I can already tell it is going to change my life! Thank you so much. I am due for a new office chair at work and want to get one in line with your principals. The back of the book mentions a pdf about chairs but I haven't been able to find it on your web site. Do you have a summary or description of what kind of office chair is best? If not, I'll just go by the general principals discussed in the book about chairs. Thanks!