An apparatus is provided for recording information about an event resulting in application of a force to a body. The apparatus comprises data recording means for recording the information, sensor means for sensing a parameter which enables a predetermined source of force to be distinguished from another, different source of force, and control means responsive to the sensed parameter for controlling the data recording means. The sensor means may comprise a pressure sensor for sensing shockwaves resulting from an explosive force and the resulting signal used to distinguish from other events, such as blunt impacts. The pressure signal may be used to control the storage of acceleration data for injury analysis.