Nope, he is just plainly an actor. Nothing more. But I do notice that he is very devoted in his work and tries to make his characters as practical as they can possibly be.
According to the special features section of Taken 2, Liam studied a hybrid mixture of Jiu Jitsu and maybe a little bit of Escrima from an ex-French Special Forces soldier.
* All of the action scenes were pre-choreographed and Liam used his knowledge that he gained from the French instructor to film the scenes.
Just to validate my reasoning, I have found an interview featuring Liam himself. He specifically stated that he does not any martial arts what so ever.