Although Lundgren has never competed as a professional bodybuilder, he has been closely associated with bodybuilding and fitness since his role as Drago in the mid-1980s. Bodybuilding.com said, "Looking like a man in his 30s rather than his 50s, Lundgren is the poster boy of precise nutrition, supplementation and exercise application that he has practiced for over 35 years." In an interview with them, he claimed to often train up to six days a week, usually one-hour sessions completed in the morning, saying that "it's just one hour a day, and then you can enjoy the other 23 hours". Although he had begun lifting weights as a teenager, he cites co-star Sylvester Stallone as the man who got him into serious bodybuilding for a period in the 1980s after he arrived in the U.S. Stallone had a lasting influence on his fitness regime and diet, ensuring that he ate a much higher percentage of protein and split his food intake between five or six smaller meals a day. Lundgren has professed never to have been "super strong", saying that, "I'm too tall and my arms are long. I think back then [Rocky IV] I was working with around 300 pounds on the bench and squat."  In a January 2011 interview with GQ he announced he is working on releasing his own range of vitamins and supplements. He wrote an autobiographical fitness book, Train Like an Action Hero: Be Fit Forever, published in Sweden (by Bonnier Fakta) on 9 August 2011, offering tips he learned over the years to work out in various situations (with a busy schedule and a lot of traveling). On 9 September 2014, Lundgren published Dolph Lundgren: Train Like an Action Hero: Be Fit Forever, a book which contains a detailed account of his earlier life and troubles. He cites a better quality of life as having inspired him to maintain his physical fitness.  When in Los Angeles he trains at the Equinox Gym in Westwood and when at home in Marbella, Spain, he trains at the Qi Sport Gym in Puerto Banus. Dolph does, however, also like to spar and practice his karate in the gym to keep in top shape aside from weight lifting. He cites dead lifting and squats as the best exercises for muscle building. Lundgren is not a heavy drinker, but has professed on many occasions to being fond of tequila and cocktails, citing his knowledge in chemical engineering as "making really good drinks".

Answer this question "why did he decide to do that" by extracting the answer from the text above.
after he arrived in the U.S. Stallone had a lasting influence on his fitness regime and diet,