Temporal correlations in center of body mass fluctuations during standing and walking

Body fluctuations during both quiet standing and walking exhibit temporal correlations that reflect mechanisms of balance control. However, knowledge about the relationship between the temporal structures observed during standing and walking is limited. The goal of the present study was (1) to investigate temporal correlations in the fluctuations of the center of body mass acceleration (ACC) in standing and walking, and (2) to test the hypothesis that the degree of the temporal correlation for the two tasks is similar and correlated across participants. Seventeen young, healthy participants stood and walked for 10 min on a treadmill equipped with two force platforms. The temporal correlations of the ACC in the anteroposterior (ACCAP), mediolateral (ACCML), and two-dimensional (ACC2D) directions were evaluated using the scaling index (α) as calculated with Detrended Fluctuation Analysis. The scaling indices of ACC fluctuations during standing and walking were categorized as stationary signals which are temporally correlated (0.5 < α < 1.0). Further, there were significant, positive correlations for ACCAP and ACC2D between the scaling indices during standing and walking. The results suggest that there are common characteristics in the balance control system for standing and walking, which may be associated with temporal correlations in COM acceleration.