SAN JOSE, Costa Rica — Jeremy Lusk, an American freestyle motocross racer, died of head injuries today after crashing while trying to land a backflip in competition. He was 24.

Jorge Ramirez, chief of the intensive care unit at Calderon Hospital where Lusk was taken, said the motocross racer suffered severe brain damage and a possible spinal cord injury.

Lusk won a gold medal at the 2008 X Games. He was injured Saturday night when he failed to complete a full rotation while attempting a Hart Attack backflip and slammed headfirst into the dirt. Lusk crashed in almost identical fashion in the freestyle semifinals at the 2007 X Games but was not hurt.

He had a successful 2008 season, winning Freestyle gold at the X Games and silver in Best Trick when he landed the first double-grab Hart Attack backflip. He won a bronze helmet in Freestyle at the Moto X World Championships in his hometown of San Diego.

Ramirez said Lusk died with his parents and his wife, Lauren, at his side.

"He was in a medicine-induced coma as a protective measure, and the medicine was being reduced to see how his organism responded," he said. "That didn't mean he was going to wake up. He was in shock and that got worse last night, until he stopped responding and entered into cardiac and respiratory failure."

Lusk lived in Temecula, Calif.