Concurrent Validity of a Commercial Wireless Trunk Triaxial Accelerometer System for Gait Analysis.

CONTEXT: Wearable sensor devices have notable advantages, such as cost-effectiveness, easy to use, and real-time feedback. Wirelessness ensures full-body motion, which is required during movement in a challenging environment such as during sports. Research on the reliability and validity of commercially available systems, however, is indispensable.

OBJECTIVE: To confirm the test-retest reliability and concurrent validity of a commercially available body-worn sensor-BTS G-WALK® sensor system-for spatiotemporal gait parameters with the GAITRite® walkway system as golden standard.

DESIGN: Reliability and concurrent validity study.

SETTING: Laboratory setting.

PARTICIPANTS: Thirty healthy subjects.

MAIN OUTCOME MEASURES: Spatiotemporal parameters: speed, cadence, stride length, stride duration, stance duration, swing duration, double support, and single support.

RESULTS: In terms of test-retest reliability of the BTS G-WALK® sensor system, intraclass correlation coefficient values for both the spatial and temporal parameters were excellent between consecutive measurements on the same day with intraclass correlation coefficient values ranging from .85 to .99. In terms of validity, intraclass correlation coefficient values between measurement systems showed excellent levels of agreement for speed, cadence, stride length, and stride duration (range = .88-.97), and showed poor to moderate levels of agreement (range = .12-.47) for single/double support and swing/stance duration. Bland-Altman plots showed overall percentage bias values equal to or smaller than 3% with limits of agreement ≤15% (speed, cadence, stride length, stride duration, swing duration, and stance duration). Only for single and double support, the limits of agreement were higher with, respectively, -15.4% to 19.5% and -48.0% to 51.4%.

CONCLUSION: The BTS G-WALK® sensor system is reliable for all measured spatiotemporal parameters. In terms of validity, excellent concurrent validity was shown for speed, cadence, stride length, and stride duration. Cautious interpretation is necessary for temporal parameters based on final foot contact (stance, swing, and single/double support time).