A solution for measuring a cardiogram of a user is disclosed. According to an aspect, a portable training computer includes a communication circuitry including a radio frequency antenna and configured to transmit a radio frequency signal through the antenna, a measurement circuitry coupled to the antenna and configured to measure an electric property of the antenna, and at least one processor configured to, in a first measurement mode, detect presence of an object in proximity with the antenna on the basis of the measured electric property, and in a second measurement mode, detect motion of a body of a user of the portable training computer with respect to the antenna on the basis of the measured electric property and compute a cardiogram of the user in the basis of the detected motion.