Part Three: Calculating the Impossible, 2-Hour Marathon Attempt

CHICAGO (CBS) -- Athletes take Sunday to Chicago's streets for the Shamrock Shuffle, the unofficial opener to the running season.

And as they set goals for the year, one Chicago doctor is reminding them they won't speed up without slowing down.

WBBM's Rick Gregg spoke with Dr. Philip Skiba of Advocate Health Care to get training tips for pros and Joes alike.

Dr. Skiba is also part of a team that's trying to run a full marathon in under two hours - this year. To hear the full interview, click here.