The Center of Pressure and Onset Latency of Electromyograms of the Supporting Leg in Upward Stepping with the Transverse Tarsal Joint Limited by Taping

Abstract

The purpose of study was to examine the changes of center of pressure (COP) and onset latency of electromyograms of the supporting leg in a motion consisting of elevation of the leg from standing to hemi-standing (raising one leg to 90° of hip flexion) with limitation of the transverse tarsal joint on the supported side. Six healthy subjects, with a mean age of 23.2 years, participated in this study. We limited range of motion (ROM) in the transverse tarsal joint on the supported side in hemi-standing by using taping. Subjects were instructed to perform a motion consisting of elevation of the leg from standing to hemi-standing. Subjects were prompted with a signal for the motion, and performed the motion as quickly as possible. A three-dimensional analysis system was used to compare both the initiation time and end time about the degree of hip flexion. A force platform was used to record the trajectory of COP during the motion. Electromyograms (EMG) were recorded from the tibialis anterior, gastrocnemius, peroneus longus, semitendinosus, rectus femoris and gluteus medius on the supported side. We also calculated the onset latency of muscle activities. We examined the trajectory of COP and the onset latency of electromyograms in the case of limitation and compared them with those in the case of no limitation. The maximum amplitude of the trajectory of COP toward the unsupported side decreased in the case of limitation compared with that in the case of no limitation. The latency at the time of maximum amplitudes of the trajectory of COP did not alter between the cases of limitation and no limitation. The onset latency of only the gluteus medius muscle was prolonged in the case of limitation compared with that in the case of no limitation. The COP primary moves to the unsupported side in gait initiation. It is generally thought that body shifts passively to the supported side due to the movement of COP from the center of the base of support to the unsupported side. From the results of this study, the decrease of maximum amplitude of the trajectory of COP toward the unsupported side shows that the whole body passively shifts to the supported side. We consider that the elongation of the onset latency in the gluteus medius muscle is related to the decrease of the maximum amplitude of trajectory of COP toward the unsupported side. This study provides evidence that limitation of the transverse tarsal joint causes compensatory movement of the pelvis in motion consisting of elevation of the leg from standing to hemi-standing.