Relaxation Induced by Comfortable Thermal Stimulation of the Feet Presented with Various Sensory Stimuli: Evaluation via Autonomic Nervous Activity

We examined the degree to which relaxation was induced by the presentation of a comfortable thermal foot stimulation paired with other sensory stimuli. We presented a movie of an underwater scene, classical music, light blue illumination, vibrations to the trunk, and grapefruit odor as relaxing stimuli in combination with thermal stimulation, and measured physiological responses of the autonomic nervous system (electrocardiogram, respiration, fingertip pulse wave, peripheral blood flow, and sweating). All stimulus combinations induced parasympathetic activation compared with an initial control. In particular, the presentation of an odor with thermal stimulation elicited a remarkable degree of parasympathetic activation. We verified differences in the latency and duration of physiological responses depending on the stimuli combination. However, subjective relaxation was not confirmed, and parasympathetic activation for combined stimuli did not remarkably differ from that for thermal stimulation alone. These results indicate that thermal stimulation has a powerful effect on relaxation induction.