This research verified changes in composition in various parts of the body caused by conductive heat and the influence of the body composition on the effect of the contra-lateral thermal reaction in order to clarify factors for improving the effect of local bathing. The body composition was investigated by means of Segmental Bioelectrical Impedance Analysis. The percentage of fat was 14.23±2.40% in men and 29.60±7.66% in women, indicating a higher percentage in women than in men (p<0.01). The volume of body fluids in lower limbs was 6.46±0.83l in the right limb and 6.39±0.86l in the left limb of men, and 4.78±0.49l in the right limb and 4.78±0.49l in the left limb of women, indicating a higher value in men than in women (both p<0.01). During each bathing, the volume of body fluids on the surface, in deep part 1 and deep part 2 of men reached a maximum earlier than that of women.
Conclusions: 1) In bathing using external conductive heat, sebaceous is a large factor for changes in temperature both on the surface and in deep parts. 2) In bathing part of the body, there is little movement of total body water (TBW) and fluids inside the body eliminating risk factors of bathing such as the oligohidria, suggesting that bathing is a safe treatment for elderly people. 3) In the contra-lateral thermal reaction using conductive heat, the possibility of increasing the effect of raising the temperature on the surface and in deep parts on the non-bathing side was suggested.

The composition of human body can be divided into five levels (atomic, molecular, cellular, tissue, and body). The objective of this study is to examine the changes with age in total body water (TBW) and fat mass (FM), which are conductive factors in the body, on the tissue level. The subjects of this study consisted of 476 healthy energetic adults living in Aomori Prefecture, Japan (146 males and 330 females). The total and partial body water and fat mass were measured by segmental bioelectrical impedance analysis. The following results were obtained after adding examination of changes in body composition with age.
1. Both males and females in their 30s showed the highest values of fat-free mass (FFM) and TBW; those in their 60s showed the highest values of %FAT and FM.
2. TBW, a thermal-conduction-promoting factor, was higher in males, and FM, thermal-conduction-inhibiting factor, was higher in females.
3. TBW in the extremities, especially in the lower extremities, tended to decrease with age both in males and females.
4. TBW in the extremities associated with the conductivity of a warm bath was higher in the lower extremities, so understanding TBW in the lower extremities can be considered very important when determining the applicability of warm bathing.