On that same year, after 10 professional fights only, he became France middleweight champion. By 1985, his successes in the ring were allowing him to train and fight full-time. In 1986, he became World Middleweight Kickboxing Champion. Kickboxing titles 1984 Middleweight kickboxing France champion 1985 Middleweight full contact kickboxing world champion -75 kg at W.A.K.O. World Championships in Budapest 1986 Middleweight kickboxing world champion Having achieved in 6 years his dream of becoming a world champion, he retired from professional kickboxing in 1987 and made the leap from athlete to actor. Gruner perception is that as soon as one reaches the top in a discipline, the only way forward is downwards. So once he had become world champion, he decided it was time to explore something else. Following the lead of Reg Park and Arnold Schwarzenegger, he chose to move on to the movie industry and become a movie star. In a very pro-active way, he did some serious self-promotion at the 1987 Cannes Film Festival. He plastered posters of himself around Cannes, which caught the attention of a producer. Days later, Gruner was flying to Los Angeles to do some screen tests. He passed those tests with a flying 74% and his next stop was the beginning of a film career. 1990s: Acting Gruner joined Imperial Entertainment Corporation (Turner Classic Movies - TCM) and began acting in action movies. Along the years, he has developed a reputation as a hard working and disciplined Hollywood actor. During this time, he has been frequently appearing in martial arts magazines, such as Budo Journal, Combat, Impact, Inside Karate, Inside Kung Fu Yearbook and many more. In 1989 he starred in his first movie; the urban action movie Angel Town. For a first timer Gruner did an admirable job, and was immediately recognized by the critics for his presence, as well as his martial arts abilities, being compared to the likes of Dolph Lundgren, Jean-Claude Van Damme, and Steven Seagall. In 1992, Gruner starred again as "Alex Raine" in Albert Pyun’s cyberpunk 1992 science fiction thriller Nemesis. The critics appreciated that Nemesis was filled with amazing stunts, thrilling action sequences, and innovative special effects that were pushing at the time the film industry limits of Blade Runner and Terminator 2. Both Nemesis and Angel town have been extremely popular in video, and Nemesis is one of the movies Gruner is most proud of.