Trainer Explains Jennifer Lawrence's Katniss Transformation

Jennifer Lawrence arrives at the Ed Sullivan Theater to tape an appearance on the Late Show With David Letterman on Tuesday (March 20) in NYC.

The 21-year-old Hunger Games star arrived in Raoul‘s diamond dress with Jimmy Choo heels and later left wearing a Prabal Gurung dress.

“[Jennifer] had a genuine excitement about [Katniss] and the role, and her opportunity to do this. I don’t think she ever saw this as stressful or hard work, she did everything she was asked to do, and never complained,” strength and conditioning coach, Joe Horrigan, told MTV News.

Their training sessions included a combination of agility drills, sprint work, running, time on the stationary bike, and lots of archery practice.

“Everything just came together and we all felt that over a period of time she became Katniss,” he added.