Born in Paris, he moved back to France in 1988 after serving in the French military and competing as a professional kickboxer, during which time he won a silver medal at the W.A.K.O.

[8][6][4] In 1978, at age 18, he joined the French Navy, volunteering for their Commandos Marine unit, also nicknamed the Bérets Verts (Green Berets).

[10] Gruner retired from professional kickboxing in 1987 and pursued an acting career, following the lead of bodybuilders Reg Park and Arnold Schwarzenegger.

[9] Although the film was not well received, Gruner's screen presence was notable, and his acting was compared favorably to Dolph Lundgren.

[12] In 1992, Gruner starred as "Alex Raine" in Albert Pyun’s Cyberpunk 1992 science fiction thriller Nemesis.

[2][13][3] Critics appreciated the amazing movie stunts, thrilling action sequences, and innovative special effects pushing the film industry limits like Blade Runner and Terminator 2.

Gruner played Jagger in Escape from Paradise (2019), and Duguay in Cyborg Nemesis: The Dark Rift (2019), and The Target (2019).

[9] Gruner had completed episodes on professional boxers, surfers, and MMA fighters,[7] when NBC decided to shelve the series, and it was never released.

But it was only starting in the 2010s, except Interceptor Force 2 in 2002, that he accumulated his involvement both as a producer, as an actor, and as a director in One Night (2010), Re-Generator (2011), Sector 4: Extraction (2014), and EP/Executive Protection (2015).

"[20] Gruner has been producing training videos for martial arts, combat skills, bodyguarding, and survival techniques since 2012.

[citation needed] Gruner is a licensed helicopter pilot, which allows him to mix this activity with film-producing requirements at times.

For example, he worked for ABC News in Los Angeles where he did many chase videos and saw a lot of damage and lethal encounters.

[5] He has been regularly maintaining his karate, boxing and kickboxing training, which he has been completing with Brazilian jiu-jitsu, wrestling and mixed martial arts.

- All Fall Down (2000) - Chameleon (2000) - Underground (2000) - The Box (2000) - Not a Bite to Eat (2000) - Dark of Night (2000) - Project Midas (2000) - Laura's Story (2000) - All the News (2000) - Sold Out for a Song (2000) - Fatal Error (2000) - Deep Down (2000) - 24 Hours (2000) - Lose Your Dreams (2000) - Thief (2000) - Bounty Hunter (2000) - Death Trap (2000) - Making Love (2000) - Tawrens (2000) - Never Go Home (2000) - The Watery Grave (2000) - The Long Drop (2000) - The Hunter (2000) - The Mission (2000) - Ethaniel's Story (2000) - The Bank Heist (2021) - Pawn Shop (2021) - Wilderness (2021)