It seems like we're not actually threatening to play g4 here (at least not immediately), since if it were our turn to play now and we played g4, then Martin could just play ...exd4, forcing us to play Qxd4 (since we have to make a capturing move) and then our g4 pawn is protected.
However, we are threatening to make a queen move (such as Qc2, which unprotects the d4 pawn and forces black to make a capturing move) and then after black plays ...exd4 we can play g4. So if Martin plays a "nothing move" here without first playing 11...exd4, then we should win easily. In the below diagram I use 11...a6 and 11...c6 as examples of "nothing moves" and show how we can beat those moves.
Nxg5