Reliability of novel centre of pressure measures of quiet standing balance in people with chronic stroke

Background People with stroke often have asymmetric motor impairment. Investigating asymmetries in, and dynamic properties of, centre of pressure movement during quiet standing can inform how well balance is controlled. Research question What are the test-retest reliabilities of novel measures of quiet standing balance control in people with chronic stroke? Methods Twenty people with chronic stroke (>6 months post-stroke), who were able to stand for at least 30 seconds without support, were recruited. Participants completed two 30-second quiet standing trials in a standardized position. Novel measures of quiet standing balance control included: symmetry of variability in centre of pressure displacement and velocity, between-limb synchronization, and sample entropy. Root mean square of centre of pressure displacement and velocity in the antero-posterior and medio-lateral directions were also calculated. Intraclass correlation coefficients (ICCs) were used to determine test-retest reliability, and Bland-Altman plots were created to examine proportional biases. Results ICC3,2 were between 0.79 and 0.95 for all variables, indicating ‘good’ to ‘excellent’ reliability (>0.75). However, ICC3,1 for symmetry indices and between-limb synchronization were <0.75. Bland-Altman plots revealed possible proportional biases for root mean square of medio-lateral centre of pressure displacement and velocity and between-limb synchronization, with larger between-trial differences for participants with worse values. Significance These findings suggest that centre of pressure measures extracted from a single 30-second quiet standing trial may have sufficient reliability for some research studies in chronic stroke. However, for clinical applications, the average of at least two trials may be required. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by the Canadian Institutes of Health Research (MOP 133577). The authors acknowledge the support of the Toronto Rehabilitation Institute; equipment and space have been funded with grants from the Canada Foundation for Innovation, Ontario Innovation Trust, and the Ministry of Research and Innovation. These funding sources had no role in the design or execution of this study, analyses or interpretation of the data, or decision to submit results. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Research Ethics Board of the University Health Network gave ethical approval for this work I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The participants of this study did not give written consent for their data to be shared publicly, so supporting/raw data is not available.