Evaluation of Wearable Sensor Placement for Movement Bout Duration Estimation: A Comparative Feasibility Study

Wearable sensor placement can influence movement quantification, yet direct comparisons across anatomical sites remain limited for bout-level temporal outcomes. This study evaluated seven IMU placements for movement bout duration estimation. Twenty-seven healthy adults performed three whole-body tasks (walking, Timed Up and Go, and Step Test) and two upper-limb tasks (reaching and hand-to-mouth) under concurrent optoelectronic motion capture. IMU-derived durations were compared with segment-specific local references and, for whole-body tasks, a common sacral reference used as a proxy for whole-body movement. Agreement was assessed using Spearman’s correlation, ICC, Bland–Altman analysis, and MAPE. Participant-level agreement analyses were complemented by trial-level repeated-measures analyses to account for within-participant variability across repeated trials. A descriptive composite ranking combined ICC, MAPE, and limits-of-agreement width against the common reference. Performance varied across placements and tasks, with the largest local–common dissociation observed during the TUG. The sacrum obtained the most favorable overall composite ranking score (2.78), closely followed by the dominant ankle (2.89) and non-dominant wrist (3.11). Both wrists showed high agreement during upper-limb tasks (ICC = 0.879–0.994). Trial-level analyses confirmed a significant effect of sensor placement for all whole-body tasks, while no significant differences were observed between wrist placements during the isolated upper-limb tasks. The non-dominant wrist showed a favorable combination of performance across movement domains, supporting its selection as a promising candidate for further evaluation in subsequent free-living monitoring.