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Contribution Of The Loading-Unloading Balance Mechanism With Various Foot Placements

Balance and motor control are affected in concussed athletes. Despite the use of standing balance tests in concussion diagnosis, the required foot placements are often inadequate for the outcomes to be sensitive to concussion recovery. Winter et al (1996), suggested that the primary motor mechanisms used can be determined from additional foot placements. To our knowledge, these additional foot placements have not been pursued in concussion research or another field. The objective of this research is to examine whether a continuum of balance motor mechanisms exists during various foot positions. We hypothesize that as the difficulty of each stance increases, one’s natural reliance on the loading and unloading mechanism of balance will increase. Understanding this information will allow concussion researchers to utilize appropriately difficult stances while also evaluating the overreliance on irregular motor systems. Each participant stood still in various foot positions repeated on the opposite foot with eyes open and closed (side by side (0 deg), 30 deg, 45 deg, 60 deg, and tandem (90 deg)). A force platform under each foot sampled at 1000 Hz, filtered at a 6 Hz cut-off was transformed into the center of pressure (COP). These COP signals were mathematically computed into two mechanisms: 1) coordinated joint control (COPc) and 2) loading and unloading each limb (COPv). The reliance on the load/unload mechanism was assessed using the total range of the COPv. Our initial results demonstrate that the range of COPv gradually increases from 0 to 90 degrees. This finding indicates a systematically increased involvement of the loading/unloading mechanism with increasingly challenging stances. These methods will allow therapists treating concussions to recognize the level of motor compensation present. Restoring the typical motor mechanism of coordinated joint control—instead of loading/unloading—in a patient could be an intervention target for athletes recovering from a concussion.