Shvartz E, Reibold R C, White R T, Gaume J G
Aviat Space Environ Med. 1982 Mar;53(3):226-31.
Six young men were administered an orthostatic test, 20 min of quiet standing before and after 5 h of quiet sitting, to determine the effect of sitting fatigue on orthostatic responses. Hemodynamic responses were recorded with an impedance plethysmograph. During the 5 h sitting period, there was a 15.6% decrease in calf blood flow, a 19.4% increase in venous pooling in the calf, and an increase in blood pressure. A comparison between the two standing tests showed increases in blood pressure and in total peripheral resistance, decreases in heart rate (7 beats/min), cardiac output (12.7%) and calf blood flow (18.5%), and 70% increase in calf venous pooling after sitting. The results show that prolonged sitting constitutes a mild orthostatic stress where an increase in venous pooling is compensated by an increase in blood pressure. When this is followed by standing, insufficient compensations are made to the large amounts of pooling resulting from both postures. Despite the maintenance of a stable blood pressure (same as at the end of the sitting period) there is an insufficient increase in total peripheral resistance and heart rate resulting in a relatively low cardiac output. Thus, prolonged sitting constitutes a liability for subsequent performance in an upright position unless methods to minimize venous pooling are employed.
对六名年轻男性进行了直立试验，即在安静坐立5小时前后分别进行20分钟的安静站立，以确定坐立疲劳对直立反应的影响。使用阻抗体积描记法记录血流动力学反应。在5小时的坐立期间，小腿血流量减少了15.6%，小腿静脉淤血增加了19.4%，血压升高。两次站立试验的比较显示，坐立后血压和总外周阻力增加，心率（每分钟7次）、心输出量（12.7%）和小腿血流量（18.5%）减少，小腿静脉淤血增加70%。结果表明，长时间坐立构成轻度直立应激，静脉淤血增加通过血压升高得到补偿。随后站立时，对两种姿势导致的大量淤血补偿不足。尽管血压保持稳定（与坐立结束时相同），但总外周阻力和心率增加不足，导致心输出量相对较低。因此，除非采用减少静脉淤血的方法，长时间坐立会对随后的直立姿势表现产生不利影响。
