Accuracy of the ActiGraph wGT3x-BT for step counting during inpatient spinal cord rehabilitation

Objectives
(1) Assess the accuracy of the ActiGraph wGT3x-BT accelerometer to count steps taken by inpatients with incomplete spinal cord injury (iSCI) in physical therapy (PT) sessions and self-directed activities, and (2) compare the number of steps/min taken in PT sessions to that in self-directed activities during inpatient rehabilitation.

Setting
Inpatient spinal cord injury rehabilitation.

Methods
Seventeen individuals with subacute motor iSCI were observed for up to 45-min of both PT and self-directed activities, during which steps were simultaneously tracked by the ActiGraph wGT3x-BT and a researcher using a hand tally counter. Accuracy was evaluated with an intraclass correlation coefficient (ICC) for the entire PT session and self-directed activities, as well as for periods of walking.

Results
There was excellent agreement between the ActiGraph wGT3x-BT and manually counted steps for entire PT sessions (ICC = 0.86) and walking periods (PT walking, ICC = 0.99; self-directed walking, ICC = 0.99). There was poor agreement for entire self-directed sessions (ICC = 0.15). Visual analysis of Bland–Altman plots supported these findings. Participants took more steps/min in PT sessions compared to self-directed activities (p = 0.023).

Conclusion
The ActiGraph wGT3x-BT accurately counts steps during PT sessions and walking periods in individuals with subacute motor iSCI. Clinically, this may enable physical therapists to track walking repetitions during inpatient rehabilitation more effortlessly.