Jennifer keeps fit by running around horse track

Jennifer Aniston has been running hard to maintain her fitness while shooting new film The Bounty.

The actress reportedly woke up at 5am in the morning and ran laps around New Jersey's Monmouth Park racecourse to the surprise of the crewmembers.

"She showed up every morning at 5am to run laps on the giant oval for a solid hour before cameras rolled," Contactmusic quoted a source as saying.

"She's really disciplined about keeping fit. She'd get there before everyone else and zip around that huge track like a winner!" the source added.

The Break-Up actress apparently prefers running to other fitness regimes as it keeps her thighs and calves toned.

Even earlier this year, it was reported that she woke up at 3am to work out so that she could stick to her busy shooting schedule.

A source said at the time: "Jennifer has had a total overhaul for this film. She wants to be seriously fit, yet remain curvy."

"There are a lot of early starts on set, so she has had to get up at 3am to get two hours in the gym before getting ready for filming."