He had a heart attack Saturday night in Fremont, Ohio, Memorial Hospital spokeswoman Chasity O'Neill said Sunday. Lytle had been taken by ambulance to the hospital with heart attack symptoms, she added.
"I knew he had some issues with a stroke a while back, but I don't know if that was related," former Michigan teammate Rick Leach said. "I do know he was a special guy, who was a mentor to me. He was one of the toughest guys I ever played with and one of the best leaders, who made the ultimate sacrifice for us by playing fullback at times."
Lytle was drafted by the Broncos in the second round in 1977. He scored on a 1-yard run in Denver's 27-10 loss to Dallas in the Super Bowl. He played seven seasons with the Broncos and scored 14 times in the regular season.
"Rob was a teammate and an incredibly terrific guy," Michigan athletic director Dave Brandon said. "When I heard the news this morning, I was sickened by it. It's a sad day because we've lost someone who was a great example of a Michigan man."
He helped the Wolverines win three Big Ten titles and ran for 3,317 yards - the highest total in school history at the time - and scored 26 touchdowns. For the Broncos, he had 1,451 yards rushing and 562 yards receiving.
Lytle grew up in Ross, Ohio, and graduated from Fremont Ross High School. He worked for Old Fort Banking Company as a vice president in Fremont.