Power spectral and microvector frequency analysis of dynamic standing foot force patterns in a normal male subject

Power spectral and microvector frequency analyses of dynamic standing foot force patterns in a normal male subject were performed using a multiple-trial experimental protocol. Power spectral analysis of eight eyes-open vs. eyes-closed 50-sec trials revealed significant power increases in the 0.14 to 0.66 Hz range with eye closure, which were repeatable in trials performed on the same subject 2 wk later. Since power spectral differences are difficult to interpret biomechanically, a (micro)vector analysis of 1/20 sec changes in proportional weight transfer was employed. This methodology was able to reveal that foot force weight transfer exhibited a distinct preferred directionality, and that the eyes-closed condition was characterized by significant increases in both the occurrence and average magnitudes of these preferred microvectors.