The Repeatability of the Instrumented Timed Up & Go Test: the Performance of Older Adults and Parkinson’s Disease Patients under Different Conditions

The Timed Up & Go (TUG) test is a simple test for gait and balance that requires no special equipment and can be part of a routine clinical examination. Combined with the development of motion capture technologies, the possibilities of assessing individual TUG sub-components (i.e. sit-to-stand, gait, turn, turn-to-sit) are increasing. The clinical evaluation of an instrumented TUG requires reliable values. We analysed the intra-session repeatability of the iTUG sit-to-stand, gait and turn parameters in three conditions: (1) single, (2) cognitive dual-tasks, and (3) manual dual-tasks in older adults and Parkinson's disease (PD) patients. The repeatability coefficient (RC) was calculated for each of the 18 parameters. The repeatability varied across subject groups, the performed tasks, and the TUG subcomponent. The gait subcomponent had 6 non-repeatable spatio-temporal parameters and 2 non-repeatable parameters for the arm swing. The parameters of the turn subcomponent can be considered as non-repeatable in both groups under the manual dual-task condition and in HC under the single-task condition. When comparing PD to HC, the repeatability of the majority of the single-task parameters was higher in PD whereas lower under dual-tasks. In PD, the major part of gait parameters had a higher repeatability under single-tasks than dual-tasks. In contrast, HC exhibited better repeatability of dual-tasks than single-tasks. Repeatability can be used to assist researchers and clinicians to select adequate parameters with respect to the purpose of motion assessment.