U.S. bobsled driver Steven Holcomb ran a little harder on an injured calf and is confident he'll be close to full speed for the four-man competition.

Holcomb is trying to win a second consecutive gold medal in four-man, which begins with two heats Saturday. Holcomb said his strained calf muscle is "about 75 percent" and he pushed harder at the start of two training runs with his three-man USA-1 crew.

He had the fourth and sixth fastest times during Friday's practice sessions, an improvement from Thursday when he was 17th and 16th among 30 sleds.

Holcomb ended a 62-year medal drought for the U.S. team in two-man, winning bronze earlier this week. He was beaten by Russia's Alexander Zubkov, who will try to win his country's first gold in four-man.