This study examined the possibility of measuring the workload during underground walking by conducting experiments and performing power spectrum analysis of heart rate variability during walking. A preliminary experiment analyzed heart rate variability in the application of a load of calculation tasks. The results indicated that the change in the frequency component (PSB) under load could be measured in seconds by performing power spectrum analysis of heart rate variability using wavelet transformation. The experiment of underground walking analyzed the relationship between the change in the extracted frequency component (PSB) and walking behavior by performing power spectrum analysis of the heart rate during walking. The results revealed that the PSB increased at the points where the subjects used stairs or made a turn at a crossing while walking, and indicated that the workload during underground walking could be measured.
