An iPhone application for upper arm posture and movement measurements

There is a need for objective methods for upper arm elevation measurements for accurate and convenient risk assessments. The aims of this study were (i) to compare a newly developed iOS application (iOS) for measuring upper arm elevation and angular velocity with a reference optical tracking system (OTS); and (ii) to compare the accuracy of the iOS incorporating a gyroscope and an accelerometer with using only an accelerometer, which is standard for inclinometry. The iOS-OTS limits of agreement for static postures (9 subjects) were -4.6 degrees and 4.8 degrees. All root mean square differences in arm swings and two simulated work tasks were <6.0 degrees, and all mean correlation coefficients were >0.98. The mean absolute iOS-OTS difference of median angular velocity was <13.1 degrees/s, which was significantly lower than only using an accelerometer (<43.5 degrees/s). The accuracy of this iOS application compares well to that of today's research methods and it can be useful for practical upper arm measurements. (C) 2017 The Authors. Published by Elsevier Ltd.