Charles Gaines, an author whose work, particularly “Pumping Iron,” was instrumental in popularizing professional bodybuilding and introducing Arnold Schwarzenegger to a global audience, died Tuesday. He was 84.

Gaines' daughter, Greta Gaines, announced his death in a tribute but did not disclose the cause.

In 1974, Gaines collaborated with George Butler to publish “Pumping Iron: The Art and Sport of Bodybuilding.” The book offered a look into what Gaines described in its introduction as “a sort of respectful report from the interior of an interesting, colorful and heretofore ignored region of American life.” In a later edition, Gaines acknowledged that neither he nor Butler initially anticipated significant interest in the book beyond the bodybuilding community. He credited Schwarzenegger with bringing the sport “out of the shadows” and into the public eye.

The book served as the foundation for the 1977 documentary “Pumping Iron,” which documented the rivalry between Schwarzenegger and fellow bodybuilder Lou Ferrigno during the Mr. Olympia competition. Schwarzenegger, a seven-time Mr. Olympia winner, leveraged the attention from the film and book into a successful acting career before entering politics and serving as governor of California from 2003 to 2011.

Gaines had been involved with bodybuilding since he was 16, beginning to lift weights at that age. The initial “Pumping Iron” project began as an article for Sports Illustrated in 1972, focusing on a bodybuilding competition.

Schwarzenegger reflected on Gaines' influence, stating on Instagram that he was fortunate Gaines was always exploring new avenues, which led to their collaboration and the popularization of bodybuilding. Schwarzenegger noted Gaines' adventurous spirit, mentioning his travels, fishing, and hunting expeditions.

Raised in Alabama, Gaines earned degrees from Birmingham-Southern College and the University of Iowa's nonfiction writing program. His literary career included novels such as “Stay Hungry,” which was adapted into a film that featured Schwarzenegger's first movie role, and “Dangler.” He also wrote about his extensive travels and adventures in books like “Waters Far and Near: Tales of Angling Adventure and Misadventure Around the World.”

Gaines is survived by his wife, artist Patricia Ellisor Gaines, and their three children: Greta, Latham, and Shelby Gaines.