Parents can be assured that there is no offensive content in this fitness game except for the sparring fights that take place against one of four symbolic animals (Dragon, Tiger, Mantis and Phoenix). Aside from this non-explicit violence towards (virtual) animals, the only reason I can imagine the title earned a "12+" advisory age rating in the UK is because it is aimed at a mature audience rather than children, and it provides a workout that may be considered too strenuous for younger players.
Fitness enthusiasts will probably want to give the game a wide berth unless they are particularly curious about learning the martial art Hung Gar or exercising at home (in which case I would suggest the original Kinetic over this). The first title in the series offers a more rounded workout, but Combat is certainly an intriguing experiment and players with the room space and the patience should be able to achieve a good grounding in Hung Gar, if that is their aim. However, respectfully overlooking the game's ambition, there are more appealing ways to learn martial arts and certainly better ways to stay in shape
There are no subtitles provided for Deaf and Hard of Hearing gamers, but as mentioned in my Kinetic review, these kinds of games are not very suited to subtitles and all players need to pay a lot of attention to both audio and visual feedback in order to progress. Without sound, the game would be awkward, but not impossible, to play.
Disclaimer: This title is currently only available in EU territories with no US release currently slated.