Charles Gaines, the writer whose book and documentary Pumping Iron helped launch Arnold Schwarzenegger to global fame, has died at the age of 84. Schwarzenegger paid tribute to him on social media as "a lifelong friend", crediting Gaines with introducing bodybuilding to mainstream audiences and giving him his break in Hollywood.

Born in Jacksonville, Florida, in 1942 and raised in Birmingham, Alabama, Gaines wrote more than 25 books and contributed to publications including Harper's, Sports Illustrated and Playboy. His 1974 best-seller Pumping Iron became the 1977 docudrama chronicling Schwarzenegger's rivalry with Lou Ferrigno, while his 1972 novel Stay Hungry was adapted into a 1976 film also starring Schwarzenegger. Gaines additionally co-invented the sport of paintball in 1981 and is survived by his wife, Patricia, and three children.