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Normative Data for the Sway Balance System

Brett, Benjamin L., PhD*,†,#; Zuckerman, Scott L., MD, MPH*,‡; Terry, Douglas P., PhD§,¶,║,**; Solomon, Gary S., PhD*,‡; Iverson, Grant L., PhD§,¶,║,**

doi: 10.1097/JSM.0000000000000632
Original Research: PDF Only

Objective: Static balance, postural stability, and reaction time are commonly impaired after a sport-related concussion. The Sway Balance System assesses postural sway (ie, stability) and simple reaction time using the triaxial accelerometer built into iOS mobile devices. The purpose of this study was to provide normative data for children and adolescents and to examine for age and sex differences on the Sway Balance System.

Design: Cross-sectional study.

Setting: Middle and high schools across the United States.

Participants: Participants were 3763 youth aged 9 to 21 years who completed the Sway Balance System Sports protocol in accordance with the company's recommended methods (ie, 1 acclimation trial and 2-3 baseline tests).

Independent Variables: Age and sex.

Main Outcome Measures: Sway Balance score (0-100) and Sway Reaction Time score (0-100).

Statistical Analysis: A multivariate analysis of variance examined the effects of age and sex on balance and reaction time scores.

Results: Sway Balance and Reaction Time scores significantly differed by age [F(10, 7494) = 39.68, P < 0.001, V = 0.10, ηp 2 = 0.05] and sex [F(4, 7494) = 55.29, P < 0.001, V = 0.06, ηp 2 = 0.03]. Post hoc analyses revealed that older groups generally had better scores than younger groups on all balance comparisons (ps < 0.001) and many reaction time comparisons. Girls performed better than boys on balance [F(2, 3747) = 53.79, P < 0.001, ηp 2 = 0.03] and boys had faster reaction times [F(2, 3747) = 37.11, P < 0.001, ηp 2 = 0.02].

Conclusions: Age and sex are important factors to consider when assessing Balance and Reaction Time scores using the Sway Balance System's Sports protocol in youth. We provide age- and sex-based normative values for the Sway Balance System, which will likely be helpful when using this technology to assess and manage concussions.

*Vanderbilt Sports Concussion Center, Nashville, Tennessee;

Department of Neurology, Medical College of Wisconsin, Milwaukee, Wisconsin;

#Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin

Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee;

§Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts;

Spaulding Rehabilitation Hospital, Boston, Massachusetts;

Home Base, A Red Sox Foundation and Massachusetts General Hospital Program, Boston, Massachusetts; and

**Sports Concussion Program, MassGeneral Hospital for Children, Boston, Massachusetts.

Corresponding Author: Grant L. Iverson, PhD, Department of Physical Medicine and Rehabilitation, Center for Health and Rehabilitation Research, 79/96 Thirteen St, Charlestown Navy Yard, Charlestown, MA 02129 (GIVERSON@mgh.harvard.edu).

G.L. Iverson has been reimbursed by the government, professional scientific bodies, and commercial organizations for discussing or presenting research relating to mild traumatic brain injury (mTBI) and sport-related concussion at meetings, scientific conferences, and symposiums. He has a clinical and consulting practice in forensic neuropsychology involving individuals who have sustained mild TBIs (including athletes). He has received research funding from several test publishing companies, including ImPACT Applications, Inc, CNS Vital Signs, and Psychological Assessment Resources (PAR, Inc). He has received salary support from the Harvard Integrated Program to Protect and Improve the Health of National Football League Players Association Members. He acknowledges unrestricted philanthropic support from ImPACT Applications, Inc and the Mooney-Reed Charitable Foundation. G.S. Solomon has been reimbursed by professional scientific bodies for discussing or presenting research relating to sport-related concussion at meetings, scientific conferences, and symposiums. He is a consultant for the Nashville Predators, Tennessee Titans, and the athletic departments of Tennessee Tech University and the University of Tennessee, fees paid to institution. He is also a consultant to the National Football League Department of Health and Safety.

The authors report no conflicts of interest.

B.L. Brett helped conceptualize the study, wrote the IRB application, executed the statistical analyses, helped draft the manuscript, and approved the final manuscript. S.L. Zuckerman helped conceptualize the study, helped draft the manuscript, and approved the final manuscript. D.P. Terry helped conceptualize the study and the statistical analyses, helped draft the manuscript, and approved the final manuscript. G.S. Solomon helped draft the manuscript, critically reviewed the manuscript, and approved the final manuscript. G.L. Iverson conceptualized the study, drafted several parts of the manuscript, and approved the final manuscript. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

The data for this study were provided by the company Sway Medical.

Received March 17, 2018

Accepted June 22, 2018

Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.