Ricky Bell, 29, the former star running back for Southern California who was runner-up for the 1976 Heisman trophy and played for Tampa Bay and San Diego of the National Football League, died today of cardiac arrest caused by a rare muscle disease.

Bell learned in November 1982 that he suffered from dermatomyositis, his physician, Allen Metzger, said.

"Dermatomyositis is a chronic, inflammatory muscle disease felt to be due to abnormalities of the human immune system," Metzger said. "Less than 5 percent of patients with this disease have associated heart disease of this severity."

A hospital spokeswoman said the disease caused a major vessel to rupture, and subsequent bleeding into the left side of the chest cavity caused the cardiac arrest.

Bell's 10-year-old son Ricky Jr. and his brother, Nathan, were with him when he died. Bell's wife did not reach the hospital before his death.

While at USC in 1974-76, Bell rushed for 3,689 yards for a 5.2-yard average and 28 touchdowns.

He was the nation's leading rusher as a junior with 1,875 yards, a single-season USC record later broken by Marcus Allen. Bell is third on the school's single-season rushing list -- behind Allen and Charles White and ahead of O.J. Simpson -- and seventh on the NCAA list.

Bell finished third in the Heisman trophy voting in 1975 and as a senior in 1976, behind Tony Dorsett. Although he was injured part of his senior year, he still gained 1,433 yards.

Bell was a first-round pick of Tampa Bay in 1977 and played five years for the Buccaneers under his former USC coach, John McKay.

"Ricky Bell was one of the finest football players I've ever had the pleasure of coaching," McKay said. "He was an even finer man."

Bell was traded to the San Diego Chargers in 1982, but made brief appearances in only four games before the illness ended his career.