Short communication Validating a low-cost, consumer force-measuring platform as an accessible alternative for measuring postural sway Kristin Alicia Bartlett a , Katharine Emily Forth a , Charles Shannon Layne b,c,d , Stefan Madansingh a,⇑ a Zibrio, Inc. Houston, TX, USA b Department of Health and Human Performance, University of Houston, Houston, TX, USA c Center for Neuromotor and Biomechanics Research, University of Houston, Houston, TX, USA d Center for Neuro-engineering and Cognitive Science, University of Houston, Houston, TX, USA article info Article history: Accepted 27 April 2019 Available online xxxx Keywords: Force platform Center of pressure Postural sway Balance abstract The Zibrio SmartScale is a low-cost, portable force platform designed to perform an objective assessment of postural stability. The purpose of the present study was to validate the center of pressure (COP) measure- ments in the Zibrio SmartScale. Simultaneous COP data was collected by a Zibrio SmartScale and a laboratory-grade force platform (LFP) under the dynamic motion of an inverted pendulum device intended to mimic the sway of a standing human. The inverted pendulum was placed on the Zibrio SmartScale which was placed on the LFP. The pendulum was then displaced to angles of 3° and 5° in both the anterior- posterior (AP) and medial–lateral (ML) directions. The findings of this study show low mean average error (MAE) among the measures taken simultaneously upon the LFP and Zibrio SmartScale with no appreciable difference in error in either AP or ML COP directions. Averaged over repeated trials, the MAE did not surpass 0.5 mm. This represented 0.4% of the total range (±50 to 60 mm in 5° displacement trials) of simulated COP. The results of this study strongly indicate that the Zibrio SmartScale can perform adequately as a light- weight and low-cost alternative method of COP measurement in comparison to a traditional LFP. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction Maintaining ‘‘good balance” is a critical component of daily life, and requires complex motor control utilizing multiple systems of the body (Lord and Sturnieks, 2005). In the laboratory, balance is most commonly estimated by observing an individual’s postural control during various activities using a force platform to quantify the two-dimensional projection of that individual’s center of grav- ity with respect to their base of support. This measure is referred to as center of pressure (COP) (Ihlen et al., 2013; Leach et al., 2014; Prieto et al., 1993). Laboratory force platforms (LFPs) are often considered to be the ‘‘gold standard” for assessment of postural control (Tesio et al., 2013), but their high cost (typical LFP cost >$10,000) and lack of portability (typical LFP mass > 30 kg) are barriers to widespread use. Recent studies have shown promising evidence that low-cost force measuring platforms can serve as viable alternatives for col- lecting COP data (Chang et al., 2014; Huang et al., 2013; Huurnink et al., 2013; Leach et al., 2014; O’Connor et al., 2016). The Zibrio SmartScale is a new portable, low-cost force measur- ing platform designed to collect COP data during quiet standing. It is unique in that it was designed using low-cost off-the-shelf com- ponents with scalable manufacturability in mind, positioning it to be widely available for home or clinical use in the near future, at less than a tenth of the burden (cost and mass) of a traditional LFP. The purpose of this study was to validate the Zibrio SmartScale (Fig. 1) against a ‘‘gold standard” AMTI LFP. This validation proce- dure utilized a custom-built mechanical system to produce a con- sistent and predictable set of dynamic loads, mimicking the trajectory of an inverse pendulum (Winter, 1995). In this way, a set of simulated COP sway trajectories could be captured by the Zibrio SmartScale and LFP simultaneously and compared for coher- ence and reliability. 2. Methods 2.1. Construction of inverse pendulum An inverse pendulum was constructed to simulate single degree of freedom postural sway (Fig. 2). The design mirrors that of Leach et al. (2014) and O’Connor et al. (2016) to increase confidence and https://doi.org/10.1016/j.jbiomech.2019.04.039 0021-9290/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: McGovern Campus, 2450 Holcombe Blvd, Suite X, Houston, TX 77021, USA. E-mail address: stefan@zibrio.com (S. Madansingh). Journal of Biomechanics xxx (xxxx) xxx Contents lists available at ScienceDirect Journal of Biomechanics journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com Please cite this article as: K. A. Bartlett, K. E. Forth, C. S. Layne et al., Validating a low-cost, consumer force-measuring platform as an accessible alternative for measuring postural sway, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2019.04.039