Talbott N, Wauligman K, Baldwin D; University of Cincinnati, Cincinnati, OH, USA. talbotnr@uc.edu.

PURPOSE: The purpose of this study was to determine the intertester and intratester reliability of a modified polygon method as a measurement of an individual’s base of support (BOS). SUBJECTS: Following consent, nine males and 15 females between the ages of 18-55 participated in this study. Subjects were from a sample of convenience and had no current history of musculoskeletal, neurological or cardiovascular conditions. METHODS AND MATERIALS: Subjects stood on a force plate that was covered by a clear plastic shelf. At the initiation of each trial, a piece of clear vinyl was placed over the plastic shelf. Bony landmarks on the posterior lateral border of the calcaneus, the distal lateral tip of the fifth phalange and the distal tip of the first phalange were then located on both feet. A metal pin was placed vertical to each landmark to a position just inferior to the plastic shelf and a permanent marker used to record the location of each landmark. The process was repeated three times by three different testers for a total of nine BOS measurements for each subject. Subjects were instructed not to move their feet throughout the testing session. Following completion of all measurement, points on the vinyl were connected forming a polygon and representing the subjects’ BOS. Points were plotted using graph paper and coordinates entered into a spreadsheet that calculated the area of each polygon. ANALYSES: Descriptive analyses were completed for measurements by each tester and for repeated measures between testers. Correlation coefficients were calculated to compare within tester and between tester agreement. RESULTS: Analysis showed no significant difference in BOS between testers or within multiple trials by the same tester. Correlations between all trials were high with r-values ranging from 0.96-0.99. CONCLUSIONS: Intertester and intratester reliability of the modified polygon method as a measurement of BOS is high. This objective tool offers a cost effective technique for recording BOS in the clinical setting and an alternative to more expensive camera systems. FUNDING SOURCE: None.

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