Method for detecting a fatigue undergone on at least one specific location of a hydraulic unit, wherein the fatigue undergone on the at least one specific location is detected by at least one fatigue indicator (F), said at least one fatigue indicator arranged for being remotely queried via wirings or via a wireless connection, wherein the hydraulic unit comprises a hydraulic machine provided with a runner arranged to rotate around a rotation axis as soon as said unit is in operation, the at least one specific location being on the runner, characterized in that : - the fatigue represents an accumulation of repeated loads above a given threshold; - the at least one fatigue indicator (F) is positioned away from the at least one specific location; - the runner comprises blades , each having two opposite sides called, respectively, pressure side and suction side, and extending from an external surface of a hollow hub , the pressure side and the suction side of the blades forming a section of the hydraulic surfaces, the hollow hub further comprises an internal surface opposite to the external surface , the at least one fatigue indicator is located on the internal surface of the hollow hub so that the at least one fatigue indicator is isolated from the stream of water or air circulating through the hydraulic channel when the hydraulic unit is in operation. wherein the hydraulic unit comprises a hydraulic machine provided with a runner arranged to rotate around a rotation axis as soon as said unit is in operation, the at least one specific location being on the runner, characterized in that : - the fatigue represents an accumulation of repeated loads above a given threshold; - the at least one fatigue indicator (F) is positioned away from the at least one specific location; - the runner comprises blades , each having two opposite sides called, respectively, pressure side and suction side, and extending from an external surface of a hollow hub , the pressure side and the suction side of the blades forming a section of the hydraulic surfaces, the hollow hub further comprises an internal surface opposite to the external surface , the at least one fatigue indicator is located on the internal surface of the hollow hub so that the at least one fatigue indicator is isolated from the stream of water or air circulating through the hydraulic channel when the hydraulic unit is in operation. - the fatigue represents an accumulation of repeated loads above a given threshold; - the at least one fatigue indicator (F) is positioned away from the at least one specific location; - the runner comprises blades , each having two opposite sides called, respectively, pressure side and suction side, and extending from an external surface of a hollow hub , the pressure side and the suction side of the blades forming a section of the hydraulic surfaces, the hollow hub further comprises an internal surface opposite to the external surface , the at least one fatigue indicator is located on the internal surface of the hollow hub so that the at least one fatigue indicator is isolated from the stream of water or air circulating through the hydraulic channel when the hydraulic unit is in operation. <EOS>