People run in their dreams. They are being chased and they are  running to escape what's behind them.  Analysts say it's really not someone or something else chasing them,  it's their own fears or unresolved anxieties chasing them. So it's themselves chasing themselves. This explains why they can't ever escape,  because we can't escape from ourselves.  Perhaps 'The Marathon Man' is a comment about the relentless, repetitive nature of modern achievement— taking part in and running in a race that has no clear end and no clear purpose, a race designed and managed by "paper cutout" figures whose sole job is to keep him running,  consistently distracted up the wrong path so there is no time remaining  to see exactly what the paper cutouts and their friends are really  up.