It is well known that people that sit or lie down for prolonged periods change their posture on a regular basis. Even when people are asleep on average 20-40 postural can be observed during an 8 hours period of night rest. One of the reasons that can be found in literature for this 'urge to move' is that these movements are necessary to persevere the blood flow in the tissue. The aim of this paper is to study the relation between tissue perfusion and pressure on the tissue and frequency of the load cycle. Each subject is subjected to a treatment scheme that varies in pressure and frequency of the load on the tissue. The pressure levels that are used are 2.7 kPa, 4.0 kPa and 5.3 kPa and the frequency levels that are used are loading/unloading at intervals of 5 min., 10 min., 15 min. Statistics shows that for 2.7 kPa there is a significant reduction of blood flow between time intervals of 5 min. and 10 min. (P=0.028), and 5 min. and 15 min. (p=0.009). Statistics also shows that there is no significant reduction in blood flow at the time interval of 10 minutes, for every level of pressure. This series of measurements seems to suggest that at the time interval of 10 minutes for every level of pressure the blood flow does not decrease compared to the start situation.