The effect of partial pressure on lower extremity upon skin temperature and electromyogram

Abstract

The purpose of this study was to investigate the effect of partial pressure on the lower extremity upon the skin temperature (Ts) and the electromyogram (EMG). In the measurement of Ts, the upper region of the ankle or the lower region of the thigh in the right extremity was pressured with a cuff (7cm in width) inflated at 40 or 80mmHg for 60min. The experiment was also conducted under normal conditions. Ts of the dorsal side of the feet, the lower part of the pressure region, the upper part of pressure region and a symmetrical region of pressure in the left extremity were measured while the subject was sitting. For the measurement of surface EMG, the gastrocnemius, the tibialis anterior, the vastus medialis and the vastus lateralis were measured with the knee in a bending posture for 9min. Prior to exercise, the angle of ankle joint was adjusted to get the level of contraction corresponding to about 25% of the maximum voluntary contractions (MVO of the tibialis anterior. Pressure was then applied to the leg or the thigh by a cuff inflated to 20, 40, 60 or 80mmHg during 2-7min of the work. The experiment was also conducted under normal condition. The results were as follows. Generally Ts was decreased by the pressure. However, there was no significant difference in the degree of decrease between pressures. And furthermore, the Ts of dorsal side of right foot was the same as that of left foot regardless of the pressurized region. The Ts of a symmetrical region decreased as compared with that of the pressurized region regardless of the pressurized region. It was inferred that the decrease of the Ts might have resulted from the action of a pressure reflex. In a non-active muscle (gastrocnemius), the change of %MIE (Maximum Integrated EMG) by the pressure (△MIE) was not shown regardless of the pressure region. In an active muscle (tibialis anterior), △%MIE was not shown while the thigh was pressured, however, in the case of where the leg was pressured at 80mmHg, the △%MIE decreased. It seemed that application of high pressure to a working muscle improved its work efficency. However, after release of the 80mmHg pressure the increase of %MIE created by the release of pressure until the end of work was large as compared with normal condition. It was inferred that application of the pressure to the active muscle might have produced the increment of muscle load.