There is provided a heart activity sensor structure (100), comprising: a flexible textile substrate (20)； at least two electrodes (24, 26) with an electric insulation between each of the at least two electrodes, wherein the at least two electrodes (24, 26) are applied on one side of the flexible textile substrate (20) and configured to be placed against a skin (32) of an exerciser (60) in order to measure biosignals related to heart activity； and an electrostatic discharge shield (40) applied on one side the flexible textile substrate (20) for protecting the at least two electrodes (24, 26) from static electricity.
