Comparison of sway meter and Kinovea software as a tool of measurement for the sway parameters during quiet standing: An observational study.

Background: Several attempts have been made to quantify postural sway, from simple observational techniques to advanced computer technology. Measuring sway using commercial motion tracking devices and force plates are expensive and not feasible in evaluation on non-standardised surfaces. Video cameras can be used as an affordable alternative to perform human motion capturing, and this data can be analysed using motion tracking software like Kinovea; a free, reliable software that provides valid data, and an acceptable level of accuracy in angular and linear measurements. This study evaluated the reliability of Kinovea software to measure the sway amplitude in comparison with sway meter.

Methods: Thirty-six young women were recruited by convenience to this prospective observational study. Sway amplitude of the participants were measured using a sway meter on three different surfaces, with eyes opened and closed conditions, using modified Lords sway meter and videography. Videos were later analysed using Kinovea motion analysing software. The quantitative data of sway parameters were analysed for reliability using intraclass-correlation co-efficient and Bland Altman plot.

Results: There was an excellent correlation (>0.90) between the sway measurement values obtained from both methods irrespective of the surfaces. But the reliability was greater for the medio-lateral sway on the pebbled surfaces (0.981), and least for the anterior posterior sway on the same surface.

Conclusion: This study concludes that, there is an excellent reliability for the video based sway analysis using Kinovea software. Hence this method can be used as an affordable alternative to measure the sway parameters.