## 4 Discussion
In contrast, for limbs with compression stockings, the rate of change in the gastrocnemius muscle circumference increased only slightly after the 3-hour sitting task (+1.9 \(\pm\) 0.6% for limbs without compression stocking vs. +0.4 \(\pm\) 0.3% limbs with compression stocking; \(p<0.05\)), and the lower limb extracellular water/total body water ratio did not exhibit any significant change. This is believed to be due to the following effects of wearing compression stockings: Tightening of the veins due to increased skin surface pressure, reduction of blood stagnation, and increased venous reflux while preventing physiological counterflow due to the physiological venous valve function. Due to these effects, compression stockings were successful for optimizing the equilibrium of the hydrostatic pressure gradient between the intravascular and interstitial spaces, thereby suppressing the onset of edema. The elastic stockings recommended by the Lower Leg Ulcer/Varies Diagnosis and Treatment Guidelines published by the Japanese Dermatological Association [16] are those that place the greatest pressure on the ankle and gradually lower the pressure toward the proximal aspect of the leg; the pressure applied to the ankle joint is less than 20 mmHg (26.7 hPa). In clinical practice, it is generally recommended that compression stockings should be applied to the ankle joint (ankle jointccalf:thigh pressure ratio of 10:7:4 or 26.7:18.7:10.6 hPa). Variable pressure is recommended to increase blood reflux from the periphery to the center. However, the robustness of evidence concerning the prevention of DVT and varices of the lower extremities in Japan is still extremely poor, and few details regarding the mechanism of the effects of wearing compression stockings on edema have been reported. Compression stockings used in this study had a pressure ratio of 8:10:8, exerting 15.7 \(\pm\) 2.8 hPa at the ankle joint, 20.1 \(\pm\) 1.1 hPa at the lateral head of the gastrocnemius muscle, and 15.6 \(\pm\) 2.2 hPa at the thigh; it was designed to place the greatest pressure at the calf region to promote muscle pump action. The pressure exerted by the compression stocking used in this study (15.7 hPa) was lower than the clinically recommended ankle pressure of 20 mmHg (26.7 hPa). Nevertheless, we observed the suppression of increases in limb circumference, of increases in extracellular water, and of decreases in skeletal muscle tissue oxygenation. Because of the low elasticity characteristic of conventional compression stockings, the potential difficulty of wearing such stockings can become an issue, resulting in decreased use [18] and an increased risk of dermatitis. The results of this study suggested the effectiveness of wearing compression stockings with lower ankle joint pressure than what is currently recommended. We investigated the effects of the compression stockings only on men in this study. However, the prevalence rate of edema among healthy subjects is 2.8 times higher in women than in men [21] The incidence of edema among aged dialysis patients is much higher in women than in men as well [22]. With this variable pressure design, we believe the utilization of compression stockings will increase in the future, in women as well as men. The absorption coefficient decreased in both limbs after the 3-hour sitting task. This was believed to be the result of decreased absorbing substance in the NIR\({}_{\text{TRS}}\) measurement region. In addition, in limbs without compression stockings, increases in the reduced scattering coefficient after the 3-hour sitting task were attributed to increased photon migration distances due to the decrease in the absorbing substance (mainly hemoglobin) in the measurement region after sitting (Table 1). The average optical path length actually increased in both limbs after the 3-hour sitting task with and without the compression stockings (Table 1).