Normative Data for the Sway Balance System

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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.


Cross-sectional study.


Middle and high schools across the United States.


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.


Sway Balance and Reaction Time scores significantly differed by age [F(10, 7494) = 39.68, P < 0.001, V = 0.10, ηp2 = 0.05] and sex [F(4, 7494) = 55.29, P < 0.001, V = 0.06, ηp2 = 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, ηp2 = 0.03] and boys had faster reaction times [F(2, 3747) = 37.11, P < 0.001, ηp2 = 0.02].


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.

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