Validity study of the standing test for imbalance and disequilibrium (SIDE): Is the amount of body sway in adopted postures consistent with item order?

The standing test for imbalance and disequilibrium (SIDE) is a discriminative measure developed for the purpose of identifying balance deficits that may cause falls. The purpose of the present study was to determine the validity of the sequence of postures used in SIDE. Subjects comprised 30 men with a mean (±standard deviation) age of 21.9±3.11 years (range 19-32 years) and 30 women with a mean age of 20.7±1.24 years (range 19-23 years). Center of pressure (COP) was measured using a stabilometer recording for 30s with a 20-Hz sampling frequency. The measurement postures that were similar to postures adopted in the SIDE were: standing with feet 20cm apart; standing with legs close and the insides of both feet touching; two tandem standing positions (with the dominant foot forward and with the non-dominant foot forward); and two single-leg standing positions (on the dominant foot and on the non-dominant foot). We calculated total path length and envelopment area of sway from the COP data. Statistical differences in means were determined using the Tukey-Kramer multiple comparison test. Results indicate that the orders of total path length and envelopment areas of sway in each posture were consistent with the item order of SIDE. Significant differences existed between the means of total path length and envelopment areas of sway in each posture (p<0.05), with the exception of both tandem standing positions and both one-leg standing positions. The item order of SIDE appears to show concurrent validity in terms of the amount of body sway in the adopted postures.