Exploring the relationship of clinical walking tests with 8-months inertial measurement unit (IMU)-based real world mobility tracking in stroke and spinal cord injury survivors.

Background: Mobility is crucial for participation and quality of life in individuals with sensorimotor impairments, yet scientific evidence on its course in real-world settings is limited. So-called wearables for measuring physical activity might help to overcome this knowledge gap allowing daily measurements of mobility. The aim of the present study is to examine the relationship between clinical walking tests and inertial measurement unit-based mobility tracking in the community setting of stroke and spinal cord injury (SCI) survivors.

Methods: At a single observational time point, the precision of the activity tracker was evaluated in a standardized parcours in healthy subjects and stroke or SCI survivors (n=57). This was followed by a multicenter observational cohort study (n=116 participants), in which the mobility of stroke and SCI survivors was assessed over 8 months immediately after discharge from acute inpatient rehabilitation. Daily distances covered in the community setting were recorded using the activity tracker. Established walking tests-including the 10-meter walk test (10MWT) and the timed up and go test (TUG)-were conducted at baseline, as well as at 4- and 8-month follow up visits. The relationship between daily distances in the ambulatory setting and 10MWT or TUG performance at discrete study visits (baseline, 4 months (midterm), and 8 months (final) after hospital discharge) was analyzed using regression models.

Results: The precision of the activity tracker in measuring covered distance in a standardized parcours varied by mobility type. The highest precision was achieved in manual wheelchair users (deviation from zero: -1.5±1.03% (p=0.15) while the least favorable precision was observed in participants with SCI and significant walking impairment (-14.6±2% (p<0.001). The widely used 10MWT speed showed a relationship with the ambulatory daily distance. The regression coefficients [m/(1m/s)] were: 874 (95% CI: 578-1171) at baseline (p<0.001), 895 (95% CI: 614-1176) at midterm (p<0.001), and 824 (95% CI: 537-1112) at the final visit (p<0.001). Interestingly, in the category of good walkers with the most favorable walking speeds the daily covered distance unmasked distinct subgroups with shorter and longer daily distances.

Conclusions: For SCI and stroke survivors, especially medium to fast walkers, activity tracking in real-world settings adds valuable insight beyond clinical walking tests. Clinical studies on rehabilitative interventions for mobility improvement should consider real-life daily distance as a key endpoint.