Could have been interesting but, not only did Neveldine-Taylor's Gamer (2009) cover this idea far more potentially, but once this descends into repetitious montages of Kellan Lutz fighting. sleeping with women, sitting in his cell, fighting again etc., it becomes a tedious action film that never thinks above the material or keeping the viewer's blood racing.
Arena had the potential to be a fun B-movie. It had the low budget, the simple but silly premise, and an excuse to give us over-the-top fight scenes that would be so ridiculous that we'd have to have a good time. All of that is wasted, and Arena wound up being a very dull experience. It's not worth watching, and feels very much like Death Race, save for a less charismatic lead and more nudity and gore.