In one embodiment a portable Device (10) for optical heart rate measurement has a first light-emitting diode (TL1), LED, for generating a light signal (Sl) having a predetermined wavelength, a detector (OR) for detecting a reflected signal (Sr1), the reflected signal (Sr1) depending on a reflection of the light signal (Sl) off a blood vessel of a user of the device (10), a stress sensor unit (PSen) for providing a pressure signal (Sp) as a function of a pressure between the portable device (10) and its user, and a control unit (CTL) connected to the first LED (TL1), the stress sensor unit (PSen) and to the detector (OR), the control unit (CTL) having a first output (Out1) for providing a heart rate signal (Sh). Therein the heart rate signal (Sh) is provided as a function of the reflected signal (Sr1) and the pressure signal (Sp) sensed by the stress sensor unit (PSen).
