Addressing core strengthening is right up there with mobility as it will prevent injury as well as increase your lifting and cardio capability, and there is no better method than planking 

It can get boring, but a static exercise such as this takes some of the injury risk away and there is no better way to strengthen the transverse abdominis which will support your spine much like a weightlifting belt around your waist.  Start with 30 second holds, progress to 60 sec, etc.

another exercise that I recommend to throw into some of your circuit programming as they demand a lot from you metabolically