A system for tracking the activity of a bedridden person comprising: - a sheet capable of covering a mattress of a bed, the sheet having a substantially rectangular outline, comprising a longitudinal side and a transverse side, the longitudinal side being of a greater length than the transverse side, the sheet comprising a contact face comprising sensors, the contact face being to be positioned on an upper face of the mattress, between the bedridden person and the upper face of the mattress, - capacitive sensors disposed on the sheet in a direction substantially parallel to the transverse side, the sensors being capable of measuring an active length corresponding to a length of sensor covered by the bedridden person, the sheet comprising a plurality of sensors disposed on the contact face, the sensors being in the form of parallel strips (13, 14), a processing unit configured to collect and analyse the active lengths of the sensors, and compare them with reference lengths, - the processing unit and the sensors being connected through à beam, first connection points being disposed at an end of each sensor in order to enable connection of the sensors to the processing unit through second complementary connection points of a beam, the sensors being secured to the sheet, the sheet comprising at least one fastening face for extending between the edge of the bed and the mattress, characterised in that the sensors extend into at least one fastening face, the first and second connection points being metal elements engaging into one another by pressure, the first connection points being positioned on a fastening face of the sheet. - a sheet capable of covering a mattress of a bed, the sheet having a substantially rectangular outline, comprising a longitudinal side and a transverse side, the longitudinal side being of a greater length than the transverse side, the sheet comprising a contact face comprising sensors, the contact face being to be positioned on an upper face of the mattress, between the bedridden person and the upper face of the mattress, - capacitive sensors disposed on the sheet in a direction substantially parallel to the transverse side, the sensors being capable of measuring an active length corresponding to a length of sensor covered by the bedridden person, the sheet comprising a plurality of sensors disposed on the contact face, the sensors being in the form of parallel strips (13, 14), a processing unit configured to collect and analyse the active lengths of the sensors, and compare them with reference lengths, - the processing unit and the sensors being connected through à beam, first connection points being disposed at an end of each sensor in order to enable connection of the sensors to the processing unit through second complementary connection points of a beam, the sensors being secured to the sheet, the sheet comprising at least one fastening face for extending between the edge of the bed and the mattress, characterised in that the sensors extend into at least one fastening face, the first and second connection points being metal elements engaging into one another by pressure, the first connection points being positioned on a fastening face of the sheet.