Investigating the AX6 inertial-based wearable for instrumented physical capability assessment of young adults in a low-resource setting

Instrumented balance and gait test are an important component of physical capability assessment in clinical examinations. This study provides insight to a new generation Open Movement inertial-based wearable (AX6, Axivity, UK) compared to a previously validated reference (AX3). The AX6 was assessed for its ability to quantify a battery of tasks that represent a composite physical capability assessment. Participants wore both wearables on the lower back (5th lumbar vertebrae) continuously throughout the testing period. No significant differences (p<0.05) were found between the AX6 and reference wearable (AX3) for time taken to complete the following tasks: four-meter walk (p=0.18), sit to stand (p=0.05), and timed up and go (p=0.55). Bland-Altman analysis plots suggest good to excellent agreement between the AX6 and reference (AX3) device with low discrepancy in mean differences and narrow limits of agreement. Significant differences were found between the AX6 and manual recorded times in the four-meter walk test and 2-minute walk test, and no significant differences in sit-tostand and timed-up-and- go were observed. Temporal data for both wearables were compared with no differences in step time, stride time, swing time and stance time. Differences were observed for spatial digital biomarker/characteristic (step length). This study shows the AX6 to be a reliable device for objectively quantifying data from physical capability tasks. These findings also reinforce the advantages of using open source, instrumented testing and methods for physical capability and disease monitoring.