Effect of Time Window on Static Balance Test Results of Children with Cerebral Palsy

It has been reported that time is an influential factor in the results of postural balance test in normal individuals and a number of studies have investigated the optimal time duration of the test, based on the convergence of data to the final results. Such information, however, is not available for children with cerebral palsy. In this research, the effect of the size and position of the time window of data acquisition on the center of pressure (COP)-based measures of the balance assessment was investigated for four cases of children with cerebral palsy. Each subject performed a single 75 seconds standing trial on a force plate and the COP trajectory was recorded. The COP-based measures of balance were then calculated and their sensitivity to the size and position of the time window was examined. It was found that the average speed of the COP had a reasonably acceptable(less than 10 percent error) stability and reliability in any time duration more than 25 seconds. It was also found that the dependency of the COPbased measures to the time window position decreases with the increase of the window size, implying that the results are more steady for a 40 seconds time window.