Unilateral DB Press
The core muscles activate to balance the torso throughout the set to you out to prevent you from falling off the bench and must engage from the start to finish of every set due to the lack of counter balance on the other side. Use a wide base by planting your feet into the ground during the entire set.
The training partner should stand on the side of the working arm ready to step in and take the weight if failure occurs or to provide minor assistance during a sticking point. Wait to form your opinions regarding the amount of core stimulation and benefit until you have completed the first 48 short training session.
Prepare for some core muscle soreness the following day or two so this is not a good workout to do for the first time a couple days before competition.
Qualified spotter required for safety.