Accuracy of the actibelt ^® accelerometer for measuring walking speed in a controlled environment among persons with multiple sclerosis

Background: Advances in portable sensor technology have opened an era for objective, real-life monitoring of walking speed in persons with multiple sclerosis (MS). Purpose: The present study examined the accuracy of the actibelt ^® accelerometer for measuring walking speed during a standard 6-min walk (6MW) and the possibility that disability status influenced the degree of accuracy among persons with MS. Methods: On a single testing session, 51 persons with MS and Expanded Disability Status Scale scores between 2.0 and 6.5 performed a 6MW while wearing an actibelt ^® in the body's sagittal symmetry plane and close to the body's centre of mass. Results: All 51 participants completed the 6MW without stopping, falling, or any adverse events, and the actibelt ^® provided walking speed data for each of the participants. The actibelt ^® significantly overestimated walking speed (actual minus actibelt ^®) by a mean±standard deviation of -0.12±0.17m/s for the overall sample (p<0.0001). There was no significant overestimation in the sample with mild disability (-0.02±0.11m/s), but there was in the samples with moderate (-0.10±0.16m/s) and severe (-0.26±0.12m/s) disability. Conclusion: The actibelt ^® is ready for real-life monitoring of walking speed in persons with mild MS, but caution is necessary when interpreting the accuracy of the walking speed data for those with MS who have moderate and severe disability.