Data analysis

To evaluate within and between sessions reliability of the parameters from the iTUG and iSway tests the Intra-Class Correlation coefficient (ICC) was used. In particular, ICC (1,1) was used for within-session reliability, since the inertial unit, the subjects and the assessor remained the same, whereas ICC (2,1) was used for between sessions reliability. The following validated thresholds for ICC values were used: ICC ≥ 0.8 excellent, 0.6 < ICC < 0.8 good, 0.4 ≤ ICC ≤ 0.6 moderate and ICC < 0.4 poor reliability. The ability of parameters to classify falls status based on falls history of a participant was also assessed using self-reported questionnaire of falls in the last 12 months.

Normality of the data was assessed using the Kolmogorov-Smirnov test. A widely used discriminant classifier model with stepwise function was performed to assess the degree to which different parameters were able to identify fall status [16, 18–20] . The discriminant function was based on Mahanolobis distance of each variable and was based on leave-one-out validation method. Statistical analysis was carried out in SPSS v22 and MATLAB (Math works, R2014a), with a level of significance set to p = 0.05.