Adjustable body monitoring system comprising: - a main body adapted to measure a physiological quantity of a user, - a wristband configured to surround a limb of the user, the strap comprising a first strap mounted on the main body and a second strap mounted on the main body , the first strap comprising a one-dimensional array of notches , the one-dimensional array of notches having a pitch p, the second strap comprising fastening means configured to be removably secured in one of the notches , each notch forming an opening through the first strap, wherein - a first face of the first strap comprises a plurality of markers , each marker being formed by a relief or a variation in color between the surface of the marker and the rest of the first face , a portion of each marker being arranged at a distance less than or equal to the pitch p of a notch associated with said marker , preferably at a distance less than half the pitch p of the associated notch , so as to form a first one-dimensional array of markers, two adjacent markers of the first one-dimensional array of markers having different shapes and/or different colors reflected by the first face , and/or different main orientations in the spatial reference frame of the first strap , - a second face of the first strap opposite the first face , comprising a plurality of markers , each marker being formed by a relief or a variation in color between the surface of the marker and the rest of the second face , a portion of each marker being arranged at a distance less than or equal to the pitch p of a notch associated with said marker , preferably at a distance less than half the pitch p of the associated notch , so as to form a second one-dimensional array of markers, two adjacent markers of the second one-dimensional array of markers having different shapes and/or different colors reflected by the second face , and/or different main orientations in the spatial reference frame of the first strap . - a main body adapted to measure a physiological quantity of a user, - a wristband configured to surround a limb of the user, the strap comprising a first strap mounted on the main body and a second strap mounted on the main body , the first strap comprising a one-dimensional array of notches , the one-dimensional array of notches having a pitch p, the second strap comprising fastening means configured to be removably secured in one of the notches , each notch forming an opening through the first strap, wherein - a first face of the first strap comprises a plurality of markers , each marker being formed by a relief or a variation in color between the surface of the marker and the rest of the first face , a portion of each marker being arranged at a distance less than or equal to the pitch p of a notch associated with said marker , preferably at a distance less than half the pitch p of the associated notch , so as to form a first one-dimensional array of markers, two adjacent markers of the first one-dimensional array of markers having different shapes and/or different colors reflected by the first face , and/or different main orientations in the spatial reference frame of the first strap , - a second face of the first strap opposite the first face , comprising a plurality of markers , each marker being formed by a relief or a variation in color between the surface of the marker and the rest of the second face , a portion of each marker being arranged at a distance less than or equal to the pitch p of a notch associated with said marker , preferably at a distance less than half the pitch p of the associated notch , so as to form a second one-dimensional array of markers, two adjacent markers of the second one-dimensional array of markers having different shapes and/or different colors reflected by the second face , and/or different main orientations in the spatial reference frame of the first strap . <EOS>