An exercise device is disclosed that provides users with a way to effectively exercise their core muscles without going to a gym. An exemplary method performed by the medical fluid injection device includes delivering a first amount of fluid to a fluid flow path, isolating fluid flow along the flow path, forming a vacuum condition upstream of the fluid isolation, re-establishing fluid communications along the flow path, and delivering a second amount of fluid to the flow path. The method includes the steps of: providing the respective die with a serial number, the plural dies being formed on the wafer; and setting up coordinates for a plane of the respective die based on one edge of the die as reference point. The central section comprises a base part and an additional part, the two articulated boreholes being embodied in the base part. The drug reservoir is compressible and adapted to contain a drug. The reader writer includes a CPU board that includes CPU and a wireless control circuit to output radio waves by a command from the CPU, an antenna that is spaced from the CPU board, and a connection cable that electrically connects the CPU board to the antenna.