Effects of a farinfrared heater that heats the feet with ceramic balls on autonomic nervous activity and mood states
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Matsui et al, 2023 [crossover trial; n = 20; female; mean age of 38.7±16.7] aimed to investigate the effects of a far-infrared heater that heats the feet with ceramic balls on autonomic nervous activity and mood states. The foot heater heats a metamorphic rock slab, which releases FIR radiation that warms the ceramic balls that in turn warm the feet. When warmed, the rock slab radiates predominantly FIR. The ceramic balls are held in a wooden container filled to a depth of about 10 cm. The participant immerses the feet in the ceramic balls up to the ankles. Participants in the FIR and control groups remained seated at rest for 10 min before participating to stabilize the autonomic nervous system. Participants underwent measurements in a seated position, with the FIR group seated for 15 min using the heater and the control group seated for 15 min. It was observed that low-frequency/high-frequency was significantly higher in the control group 10 min after the start of intervention than at baseline. Low-frequency/highfrequency was significantly lower in the far-infrared group than in the control group at 5 min, 10 min, and 15 min. High-frequency was significantly higher in the far-infrared group at 5 min, 10 min, and 15 min than at baseline. High-frequency 5 min after the start of intervention was significantly higher in the far-infrared group than in the control group. POMS2 scores improved significantly more in the far-infrared group than in the control group, including in fatigue-inertia, tension-anxiety, and total mood disturbance. Finally, the far-infrared group showed greater improvements in Two-Dimensional Mood ScaleShort Term scores such as stability and pleasure. Therefore, it was concluded that using the far-infrared heater to heat the feet with ceramic balls stabilized and improved mood, reduced Fatigue-Inertia and Tension-Anxiety, and alleviated total mood disturbance. Parasympathetic nervous system activation was observed from 5 min after the start of heating, suggesting that short-duration heat stimulation of the feet is effective.