Relationship Between Center of PPressure and Center of Mass Freuquency Measures During Single Leg Stance

Abstract

1334 Center of pressure (CP) and center of mass (CM) based variables are frequently used to quantify postural control during single leg stance. One way of assessing characteristics of balance is to use frequency spectrum analysis. Typically one or the other measurement tool may be available. PURPOSE: To determine the relationship between CP and CM frequency spectrum measures. METHODS: 17 physically active persons performed three trials (12s) of SLS (dominant limb) under both eyes open (EO) and closed (EC) conditions. During each trial, forceplate (Bertec 4060NC) and kinematic data were recorded (100 Hz). Forceplate outputs were used to determine the CP location in the anterior-posterior (AP) and medial-lateral (ML) directions. An electromagnetic tracker (Motion Monitor) collected three dimensional (3D) kinematics of the feet, shanks, thighs, pelvis, thorax, head, and upper and lower arms. Combining the kinematic data with anthropometric data allowed for the calculation of the body's CM location in the AP and ML directions. An in-house Labview analysis program was used to quantify mean power frequency (MOF), spectral area (SA), peak power frequency (PPF), and peak power (PP). Statistical significance was tested at α = .05 level. RESULTS: Significant correlations between CP and CM measures were found for EO MPF in the AP direction, SA in the AP and ML directions, PPF in the AP direction, and PP in the AP and ML directions. Significant correlations between CP and CM measures were found for EC MPF in the ML direction, SA in the AP and ML directions, and PP in the AP and ML directions. Additional statistical testing indicated that frequency analysis could distinguish between EO and EC conditions for MPF in the AP direction, SA in the AP and ML directions, PPF in the AP direction, and PP in the ML direction and for the most part CP and CM frequency values cannot be used interchangeably. CONCLUSIONS: Depending upon the variable assessed conclusions reached from frequency analysis for CP apply to CM measures.