A bulge that runs down the midline of the abdomen that tents up or pushes out when doing a crunch like activity, coughing or straining is most likely a diastasis recti.  Poor movement patterns combined with muscle weakness forces the belly to bulge and stretch the underlying connective tissue causing a separation of the abominable wall. The separation in the muscles allows what is inside of the abdomen, typically intestines and belly fat, to push through and create a bulge.