Abstract: A heart rate monitor comprises a housing (30) and an optical heart rate (OHR) sensor within the housing (30). The OHR sensor comprises a sensing unit (40) including at least one light emitter (42a, 42b) arranged to emit light into the skin of a user and a photodetector (44) arranged to sense light reflected through the skin of the user. The housing (30) comprises a domed portion (60). The sensing unit (40) is exposed through a surface of the domed portion (60) and protrudes above the surface of the domed portion (60).

Abstract: A heart rate monitor comprising an optical heart rate (OHR) sensor and a strap for mounting the sensor to a limb of a user is described. The OHR sensor comprises a sensing unit including at least one light emitter arranged to emit light into the skin of a user and a photodetector arranged to sense light reflected through the skin of the user. The sensing unit is arranged substantially centrally in the strap and the strap comprises compressible edge portions that run along opposite sides of the sensing unit such that, when the strap is mounted to a limb of a user, the edge portions are compressed against the skin to prevent or reduce the ingress of ambient light to the sensing unit.