There is provided a system, method and device for dynamically compressing an actigraphy signal at a source device. The method comprises receiving the actigraphy signal related to a user's physical activity from an accelerometer sensor on the source device and for compressing the actigraphy signal by determining regions of interest in the actigraphy signal to capture, said compressing performed by: computing a rapid change factor value indicating a drastic change in movement activity in said actigraphy signal, said rapid change factor computed based on determining a spurious free dynamic range of a second order difference signal of the actigraphy signal and subsequently determining the step size of the actigraphy signal, the step size indicating the interval with which the actigraphy signal instantaneously changes its value from one sample to another； automatically scanning the second order difference signal to locate samples in the second order difference signal having a value greater than the rapid change factor value, said located samples defining primary segment boundaries； - extracting frames of the encoded actigraphy signal between two consecutive primary segment boundaries and discarding outlying regions of the encoded actigraphy signal； and -outputting only the extracted frames representing a compressed actigraphy signal to an external computing device for subsequent processing.La présente invention concerne un système, un procédé et un dispositif permettant de compresser dynamiquement un signal d'actigraphie au niveau d'un dispositif source. Le procédé consiste à recevoir le signal d'actigraphie lié à une activité physique d'utilisateur à partir d'un capteur d'accéléromètre sur le dispositif source et à comprimer le signal d'actigraphie en déterminant les régions d'intérêt dans le signal d'actigraphie destiné à la capture, ladite compression effectuée par : calcul d'une valeur de facteur de changement rapide indiquant un changement considérable dans l'activi
