Can anyone explain the plot of Marathon Man?

Yeah, and they call it Marathon Man because he is training to be an endurance runner which helps him escape from another guy, Jameway, but Janeway in a suit and tie almost catches him even though MM had a really good head start.
Which makes MM look really weak. Well, I guess he wasn't as strong as he might have been after being tortured, but still, they should have shown his training paying off even bigger than it was.