The passage discusses the history of calisthenics, which uses only body weight for strength training. It originated in ancient Greece and was practiced by Spartan warriors and Olympians. It experienced a resurgence in the 1800s with gymnastics and strongmen performances. However, in the 1960s-70s, bodybuilding focused solely on muscle size rather than proportion, leading calisthenics to be used mainly by vulnerable groups. Overall, the passage traces the history and decline of calisthenics due to the rise of weight training and bodybuilding.