These images are all from the book Promotion & Conservation of Health Strength & Mental Energy, by Lionel Strongfort. The term "Strongfortism" is used throughout the book and is, of course, derived from the name Strongfort. As defined in the book, Strongfortism is "The Science of Promoting Physical Fitness through Internal and External Muscular Harmony". The images posted here include scans of the front and back cover of the book, and scans of some sample pages. The book is paperback, 65 pages long, and looks to have been printed circa 1930.