Sampling duration effects on centre of pressure summary measures

The purpose of the present study was to examine the effect of sample durati on on the magnitude and reliability of centre of pressure (COP) summary mea sures commonly used to characterize the control of upright stance. COP was recorded from 49 participants who stood quietly during three consecutive 12 0 s trials. Each record was subdivided into 15, 30, 60 and 120 s samples an d root mean square (RMS), mean power frequency (MPF) and mean position of C OP were calculated for each sample. RMS significantly increased and MPF val ues significantly decreased as sample duration increased. Substantial incre ases in the reliability of both RMS and MPF were observed with increased sa mple duration. (C) 2001 Elsevier Science B.V. All rights reserved.