Being one of Hollywood's leading ladies isn't all about red carpet events and promoting your latest cosmetics line...just ask Reese Witherspoon.

We spotted Reese running her little heart out on the set of her new movie, How Do You Know, in Washington DC today.

Reese stars in the movie alongside Owen Wilson but he was nowhere to be seen this morning as Reese was put through her paces, take after take.

See more pictures of Reese Witherspoon in the gallery below...

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