I was one of the individuals who interpreted the resistance exercises in the Charles Atlas Course as isometrics as did all of the other guys that I knew who took the course in the early 1950s.
The instructions were not that clear and there were no specific references to any number of repetitions.
Maybe it was oversight, maybe is was marketing genius or maybe it was an effort to separate the course from the instructions in Alois P. Swoboda's Conscious Evolution course as both Dr Frederick Tilney and Atlas were in the employ of Bernarr MacFadden when the course was written. They would also continue to be dependent on him for advertising in his magazines during the early years of the course.
During the isometric fad of the 1960s Atlas himself promoted the course as isometrics as have the current owners of the course since.
I really didn't understand the interaction of all of these events until I came across that quote by Charles Atlas stating that he owed everything to A'P. Swoboda and actually saw a copy of the Swoboda Course that I bought on the internet years later.
http://www.sandowplus.co.uk/Competit...64/life-64.htm