Experts initially questioned how the man could have got the better of the mountain lion after the surprise attack.
But a necropsy later confirmed suffocation as the cause of the animal’s death.
A spokesman for Colorado Parks and Wildlife said: “After additional investigation, including examination of the lion, we have confirmed the victim’s account that he was able to suffocate the animal while defending himself from the attack.”
He added: “The runner described hearing something behind him on the trail and was attacked by a mountain lion as he turned around to investigate.
“The lion lunged at the runner, biting his face and wrist. He was able to fight and break free from the lion, killing the lion in self-defence. He was able to suffocate the animal while defending himself from the attack.”
The encounter happened in a 2,711-acre park which has an elevation of between 5,430ft and 7,255ft, and 29 miles of hiking and cycling trails.
Mark Leslie, a parks manager in Colorado, said: “The runner did everything he could to save his life. In the event of a lion attack you need to do anything in your power to fight back, just as this gentleman did.”
Adult mountain lions, also known as pumas or cougars, can grow to 220lbs. Attacks are uncommon in Colorado. There have been three deaths and 16 injuries in the state in the last 30 years.