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Assessing the Global Range of Motion of the Helmeted Head Through Rotational and Translational Measurements

Abstract This work aimed to describe the helmeted head mobility as a combination of rotations and translations during functional head movements. A motion capture system was used to follow six optoelectronic markers placed on a motorcycle helmet worn by volunteers performing head motions (flexion-extension (FE), axial rotation (AR) and lateral bending (LB)). Maximum angular rotations and linear displacements were computed to assess intra-class correlation coefficients, standard errors of measurement and minimal detectable changes. Rotational range of motion was 101.9° (SD 17.8°) for FE, 78.8° (SD 13.8°) for LB and 124.7° (SD 27.5°) for AR. Linear range of motion was 255.8 mm (SD 53.5 mm), 217.6 mm (SD 35.7 mm) and 74.7 mm (SD 26.3 mm), respectively, for anteroposterior, lateral and inferior displacements. Assessing rotational and translational mobility of the helmeted head could also support validation of human models, and evaluate how safety devices could restrain head neck mobility before crash.