Charles Gaines, the American author whose 1974 book Pumping Iron helped bring bodybuilding into the cultural mainstream and launched Arnold Schwarzenegger's career, has died at the age of 84. His daughter, Greta Gaines, confirmed his death on Tuesday but did not disclose a cause, paying tribute to him as someone who lived life to the full.

Gaines co-wrote Pumping Iron: The Art and Sport of Bodybuilding with George Butler, drawing on a 1972 Sports Illustrated article he had written about a bodybuilding contest. The book formed the basis of the 1977 documentary of the same name, which chronicled the rivalry between Schwarzenegger and Lou Ferrigno and propelled Schwarzenegger to stardom, first in Hollywood and later as governor of California. Gaines, who was raised in Alabama and educated at Birmingham-Southern College and the University of Iowa, went on to write several other books, including the novel Stay Hungry, which was also adapted into a film. Schwarzenegger paid tribute to him on Instagram, describing him as endlessly curious and crediting him with discovering bodybuilding as "our niche sport".