Concurrent validity of a trunk tri-axial accelerometer system for gait analysis in older adults.

The aim of this study was (1) to determine the concurrent validity of a trunk tri-axial accelerometer system (DynaPort) with the GAITRite system for spatio-temporal gait parameters at preferred, slow and fast self-selected walking speed that were recorded for averaged and individual step data in an older adult population and (2) to compare the levels of agreement for averaged step data from different walking distances and individual step data. The levels of agreement between the two systems for averaged step data was excellent for walking speed, cadence, step duration and step length (intraclass correlation coefficients (ICCs) between 0.99 and 1.00, ratios limits of agreement (RLOA) between 0.7% and 3.3%), moderate for variability of step duration (ICCs between 0.88 and 0.98 and RLOAs between 19% and 34%) and low for variability of step length (ICCs between 0.24 and 0.33 and RLOAs between 73% and 87%). The levels of agreement for individual step duration and step length were moderate with ICCs between 0.81 and 0.89 and with RLOAs between 9% and 13%. Comparing RLOAs from averaged step data across the different walking distances and individual step data, the RLOAs decreased with increased number of steps. The results of this study demonstrate that the DynaPort system, which allows measurements in real life conditions, is a highly valid tool for assessment of spatio-temporal gait parameters for averaged step data across a walkway length of approximately 20m in independent living elderly. Gait variability measures and individual step data need to be viewed with caution because of the moderate to low levels of agreement between the two systems.