Heart rate monitors are becoming increasingly popular among athletes eager to gauge their performance and balance their training. Physical exercise requires concentration and usually puts our sight and hearing in use. Meanwhile, touch remains underutilized. Due to the extensive work-load of sight and hearing, heart rate monitors suffer from usability problems especially in motion.

This thesis reports a study investigating the possibility to utilize touch in conveying information between the device and the user during exercise. This idea brings up three major questions: can people detect vibrations effectively in motion, how does activity level affect recognition performance, and could touch-based interaction improve the usability of heart rate monitors? Since these kinds of questions require empirical research to be answered, a method of utilizing vibrotactile feedback in guiding interval training has been developed in this thesis. The method bases on a 20-minute interval training program implementation. The hardware produces different kinds of vibration sequences which guide the user to catch up certain activity levels.

A user experiment was conducted to reveal how the method performs. The subjects were able to detect 97,1 % of the vibration sequences and recognize 98 % out of the detected ones. The overall performance was 95,2 % which is calculated by dividing the number of correctly decoded vibration sequences with the total number of vibration sequences. The major findings are that the level of user activity affects only minimally the ability to detect vibrotactile stimuli. The users are also able to comprehend the conveyed information without problems. The conclusion derived from the observations and experiences also answers the initial question whether vibrotactile feedback could improve the usability of heart rate monitors? Yes, it could. The results suggest that vibrotactile feedback plays a key role in improving the interactions with heart rate monitors.

Keywords and terms: haptic, tactile, vibration, vibrotactile, heart rate monitoring