Eight years after winning an Oscar for "Walk the Line", Reese Witherspoon is taking another stroll towards Hollywood glory -- but this time, it's a grueling 1,100-mile solo hike.
At least that's what her character undertakes in "Wild", a film based on the best-selling, real-life story of a woman's three-month trek along the Pacific Crest Trail, which runs from California to the Canadian border.
"This movie was definitely one of the hardest movies I've made in my entire life," the 38-year-old Witherspoon told reporters ahead of the film's US release this week.
Critics have already rewarded her with glowing reviews, with the Hollywood Reporter describing it as a "vivid wilderness adventure film that is also a powerful story of family anguish and survival."
The film is based on the 2012 bestseller "Wild: From Lost to Found on the Pacific Crest Trail" by Cheryl Strayed, adapted for the big screen by award-winning British writer Nick Hornby.
Directed by Canadian Jean-Marc Vallee -- whose "Dallas Buyers Club" won three Oscars earlier this year -- the film tells the tale of Strayed's hike from the Mojave desert north along the snow-covered Sierra Nevada to Washington state.
Strayed embarked on the epic adventure at the age of 26, in part to exorcise the demons of a failed marriage and her mother's death, which had sent her into a downward spiral of sex and drugs.
- 'Gritty scenes' -
Witherspoon -- who won the Academy Award for best actress for her role in 2005's "Walk the Line", a biopic about country music legend Johnny Cash -- said: "There were so many gritty scenes that I had to tackle. That was definitely very daunting.
"The other aspect that was difficult was the emotional truth and honesty... You don't really discover why Cheryl's on this hike until halfway through the film. And as soon as you do, you're just rooting for her to finish."
Hornby -- known for his novels "Fever Pitch" and "High Fidelity", both of which were made into movies -- was responsible for adapting the book to give it dramatic momentum, partly through flashbacks.
"He did a great job restructuring the book, creating more of an emotional mystery," said Witherspoon, who co-stars with Laura Dern as her mother.
Musically, the movie has a distinctly 1960s and 70s feel starting from the first frame, when the soundtrack opens with Simon and Garfunkel's "El Condor Pasa." Other tracks include Leonard Cohen's "Suzanne" and The Hollies' "The Air that I Breathe."
Vallee said this is deliberate -- he shared playlists of the chosen songs with the cast before they even began filming, and made sure they could listen while actually shooting scenes.
"I was always trying to find an audio device to play the music so that the characters are hearing the music just like the audience, coming from a house boom box or a car radio," he said.
Some critics are already tipping the actress, and the movie, for glory in Hollywood's imminent awards season, which ends with the Academy Awards on February 22.
"Wild" scores an impressive 88 percent approval rating on movie review website Rotten Tomatoes, which says: "'Wild' finds director Jean-Marc Vallee and star Reese Witherspoon working at the peak of their respective powers."
Strayed, who has joined the filmmakers in promoting the movie, praised Witherspoon's emotional intelligence, saying "She captures, I think, a sense of seeking on that journey which I really truly had."
The writer, who is now 46, said it was "entirely bizarre" seeing the actress play her on screen.
"I don't think it can be explained how strange it is. Just imagine if you had a movie star pretending to be you on screen," she said, adding: "I feel so honored by the work she did, by the way she represented me."
"Wild" will be released across the United States on Friday, after a limited release in Los Angeles and New York on Wednesday.