Haptic Biofeedback for Wakeful Rest: Does Stimulation Location Make a Difference?

Wearable haptic interventions can support relaxation through slow, vibrotactile biofeedback. However, most applications focus on stress-inducing tasks and fixed vibration patterns, with limited attention to body placement or dynamic feedback during restful states. This study examined real-time heart rate-driven vibrotactile feedback during eyes-closed wakeful rest at four body locations: wrist, hand, forearm, and shoulder. We measured heart rate, ear-based alpha EEG, subjective restfulness, and user experience. Biofeedback reduced heart rate at the wrist, shoulder, and forearm, while alpha power remained unchanged. Restfulness ratings and location preference were highest at the forearm and shoulder. Participants also reported greater comfort, relaxation, and sleepiness at the forearm, while the wrist was more noticeable. These findings suggest the forearm and shoulder are well-suited for unobtrusive relaxation feedback, whereas the wrist may benefit from design refinement.