Movement smoothness and turning deficits during the timed up and go in older adults with chronic neck pain.

This study investigated phase-specific performance, movement smoothness, and turning kinematics during the Timed Up and Go (TUG) test in older adults with and without chronic neck pain (CNP). Eighty-five older adults [CNP, n = 25; control (CON), n = 60] completed an instrumented TUG (iTUG) using wearable inertial sensors. Total TUG duration, spatiotemporal gait parameters (gait velocity, stride length, and cadence), and phase durations (sit-to-stand, walking forward, turning, walking back, and turn-to-sit) were extracted. Trunk movement smoothness was quantified using the Log Dimensionless Jerk based on acceleration (LDLJa), and peak trunk angular velocities during turning and turn-to-sit were calculated. Compared with the CON group, participants with CNP required significantly longer to complete the TUG, particularly during the turning, walking-back, and turn-to-sit phases, despite similar gait velocity, stride length, and cadence. The CNP group also demonstrated lower LDLJa values, indicating reduced movement smoothness, together with lower peak trunk angular velocities during turning and turn-to-sit. LDLJa was positively correlated with turning angular velocity in both groups, indicating that smoother movement was associated with faster, more coordinated turning. Older adults with CNP exhibited impaired functional mobility characterized by prolonged TUG performance and reduced movement smoothness despite preserved basic spatiotemporal gait parameters. These impairments were most evident during dynamic postural transitions, suggesting that phase-specific iTUG metrics and LDLJa provide complementary information on movement quality beyond conventional TUG outcomes and may enhance the clinical assessment of mobility impairment in older adults with CNP.