부산대학교 도서관

The guidelines for heat illness prevention in Japan suggest rest and rehydration based on the heat index (WBGT) to prevent heat illness during sports. However, even with such guidelines, the number of heat illness patients has not decreased yet. We analyzed the relationship between hydration and heart rate variability (HRV) of 40 subjects measured with a wearable heart rate device. Four HRV indicators investigated (NN50, pNN50, HF, LF/HF) showed changes after drinking water. The indices of the parasympathetic nervous system (NN50, pNN50, HF) showed that the value increased 1 to 5 minutes after drinking water, and the effect continued until 20 minutes later. The index of the sympathetic nervous system (LF/HF) increased only around drinking water, and the effect disappeared after 1 minute. These results suggested that the effect of drinking water on the sympathetic nervous system appears rapidly and that the effect on the parasympathetic nervous system is sustained.