– also Milt Caniff, Hal Foster, and Roy Crane." Shuster taught himself to draw by tracing over the art in the strips and magazines they collected. As a boy, Shuster was interested in fitness culture and a fan of strongmen such as Siegmund Breitbart and Joseph Greenstein. He collected fitness magazines and manuals and used their photographs as visual references for his art. The visual design of Superman came from multiple influences. The tight-fitting suit and shorts were inspired by the costumes of wrestlers, boxers, and strongmen. In early concept art, Shuster gave Superman laced sandals like those of strongmen and classical heroes, but these were eventually changed to red boots. The costumes of Douglas Fairbanks were also an influence. The emblem on his chest was inspired by heraldic crests. Many pulp action heroes such as swashbucklers wore capes. Superman's face was based on Johnny Weissmuller with touches derived from the comic-strip character Dick Tracy and from the work of cartoonist Roy Crane. The word "superman" was commonly used in the 1920s and 1930s to describe men of great ability, most often athletes and politicians. It occasionally appeared in pulp fiction stories as well, such as "The Superman of Dr. Jukes". It is unclear whether Siegel and Shuster were influenced by Friedrich Nietzsche's concept of the Übermensch; they never acknowledged as much. Comics Comic books Since 1938, Superman stories have been regularly published in periodical comic books published by DC Comics. The first and oldest of these is Action Comics, which began in April 1938. Action Comics was initially an anthology magazine, but it eventually became dedicated to Superman stories. The second oldest periodical is Superman, which began in June 1939. Action Comics and Superman have been published without interruption (ignoring changes to the title and numbering scheme). A number of other shorter-lived Superman periodicals have been published over the years. Superman is part of the DC Universe, which is a shared setting of superhero characters owned by DC Comics, and consequently he frequently appears in stories alongside the likes of Batman, Wonder Woman, and others. Superman has sold more comic books over his publication history than any other American superhero character. Exact sales figures for the early decades of Superman comic books are hard to find because, like most publishers at the time, DC Comics concealed this data from its competitors and thereby the general public as well, but