## 1 Introduction  
Sitting has gained attention because sitting for a long period of time can cause deep vein thrombosis (DVT). Long-distance travel has become common; therefore, DVT can occur in healthy individuals as well as in those at greater risk for DVT due to spending long periods in a sitting position [1]. It is reported that thrombi formed in the deep veins of the lower extremities can be carried to the lungs through the bloodstream, leading to pulmonary thromboembolism and death [2]. The time spent in a sitting position has gained attention over the past 10 years because it is a factor independent of exercise levels [3; 4]. The longer an individual (even a healthy individual) remains in a sitting position during the course of daily activities, the higher the presence of biomarkers that are indicative of the development of diabetes and cardiovascular disease [5; 6], resulting in increased prevalence of these diseases [7] and increased all-cause mortality [8]. Current data regarding acute changes in the body as a result of extended sitting are not sufficient. Several problems have been reported as a result of sitting for long periods, such as increased calf circumference, decreased blood flow velocity in the lower extremities, and worsening vascular endothelial function [9; 10]. However, there are very few reports focusing on the influence of 3 h of sitting on lower limb skeletal muscle tissue, which is the final oxygen utilization site. Near-infrared spectroscopy (NIRS) is a technique used to measure tissue oxygenation levels. It involves irradiating tissues with two or three types of near-infrared light of different wavelengths and then detecting and analyzing the light passing through the tissue, thereby allowing for quantitative measurements of oxygen saturation and evaluations of changes in oxygenated hemoglobin (oxy-Hb) and deoxygenated Hb (deoxy-Hb) levels. Because this technique is both convenient and non-invasive, its use for assessing oxygen dynamics in various tissues, including skeletal muscle and brain tissue, has become widespread. A broadly adopted form of NIRS is near-infrared continuous-wave spectroscopy (NIR\({}_{\text{CWS}}\)), in which irradiation is performed using a continuous beam of light [11; 12]. Hb concentrations assessed using NIR\({}_{\text{CWS}}\) are calculated based on Lambert-Beer's law. However, NIR\({}_{\text{CWS}}\) is unable to determine the optical path length. Therefore, this value can be calculated based on relative changes in concentration even though quantitative measurement is impossible [11; 12]. Near-infrared time-resolved spectroscopy (NIR\({}_{\text{TRS}}\)) was developed as a measurement method that could compensate for this defect. This technique involves irradiating the target tissue with a short pulse of light, thereby allowing for independent determination of the scatter and absorption coefficients, which indicate the optical characteristics of the object, based on the time responsiveness. Therefore, when measurements were performed using NIR\({}_{\text{TRS}}\), it was possible to determine the optical path lengths that could not be measured with NIR\({}_{\text{CWS}}\), due to which it was possible to evaluate the oxygen kinetics in tissues with absolute values [13; 14]. It is now possible to measure changes over time in the same subject after maintaining a sitting position and to compare measured values among different individuals. Several methods are recommended to prevent DVT and lower extremity varies, such as walking and active exercise, wearing compression stockings, intermittent pneumatic compression, and administration of heparin and warfarin [15; 16; 17]. The advantages of compression stocking usage are not only high cost performance but also no side effects of hemorrhage, which often occurs when heparin and warfarin are administered. Compression stockings can also be used by patients who cannot move and frail elderlies.