Franco Columbu, an Italian bodybuilder whose herculean physique won him major titles in the 1960s, ’70s and ’80s, and who helped popularize the sport with his close friend Arnold Schwarzenegger, died on Friday at a hospital in Olbia, Italy. He was 78 .

His death was confirmed by a doctor at the hospital, who did not specify the cause. Italian news reports said that Mr. Columbu had become sick while swimming in the sea at San Teodoro, a beach town in Sardinia he was visiting, and that he had been taken to the hospital by helicopter.

Mr. Columbu was a talented boxer before he gravitated to powerlifting and bodybuilding in the mid-1960s. He stood under 5 feet 6 inches tall and usually weighed around 185 pounds, which might seem diminutive for an Atlas. But he sculpted his muscles enough to win titles like Mr. Universe, Mr. World and twice Mr. Olympia, one of bodybuilding’s most prestigious honors. He was nicknamed the Sardinian Samson, after the island of his birth.

“Franco Columbu was never the biggest man on a bodybuilding stage, but he was usually the strongest,” an article in Muscle & Fitness magazine said in 2012, adding that he “was a three-ring circus unto himself” who would “regularly put on a deadlifting exhibition in which he’d pull more than 700 pounds before a stunned audience.”