Visualization of heart activity in virtual reality: A biofeedback application using wearable sensors

Stress or anxiety disorders are a growing problem in industrialized countries. Those can be effectively countered by several relaxation techniques which are more effective using biofeedback. Modern virtual reality hardware provides a high level of immersion to its users. This directly affects the feeling of presence. An increased feeling of presence may allow biofeedback mechanisms to work more effectively. We build on this idea and explore how different visualizations of a user's cardiac activity in a virtual environment can be used in biofeedback scenarios - and how effective they are. Using a state-of-the-art virtual reality headset, 14 participants were subjected to four different visualizations of their own heart rate (one control visualization and three experimental visualizations). In different experiments, we examined whether they were able to estimate their heart rate based on the visualization and whether we could influence it subconsciously. Furthermore, we used the AttrakDiff questionnaire to assess the usability and attractiveness of each of the four visualizations. For the three non-reference ones, we observed significant positively correlating changes in the heart rate between the real-time true representation of the heart rate and a simulated increased heart rate visualization with a mean magnitude of 1.96 ± 0.39 beats per minute. The results from the source and number estimation experiments and the questionnaire led to the conclusion that the most appealing and best working visualization for biofeedback is a synchronized modulation/modification of the virtual environment itself.