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

Abstract

The aim of this study was (1) to determine the concurrent validity of a trunk tri-axial accelerometer system (DynaPort^®MiniMod) 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^®MiniMod 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 20 m 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.

Introduction

For clinical and research settings, objective measurements of spatio-temporal gait parameters are needed to identify possible gait impairments or to evaluate the effects of therapeutic interventions. Different valid and reliable methods exist for the assessment of gait parameters, e.g. force plates, three-dimensional motion analyses systems and pressure-activated sensors [1], [2], [3]. However, most methods are time-consuming, costly, limited to a single gait cycle and labour-intensive. As an example, the GAITRite^® system is a reliable and valid portable electronic walkway for measuring both averaged and individual step parameters in older populations [1], [4] and was designed for gait analysis in clinical settings [1], [3]. However, the relative short length of the active area of the GAITRite^® system can be a limitation in measurements of averaged step data [5]. Furthermore, it is questionable whether data collected in a laboratory environment from individual steps adequately mimic natural walking performance in daily life [6]. Therefore, user-friendly portable gait analysis systems which are able to capture data from many gait cycles and allow measurements in a more challenging context are potentially important for clinical and research settings.

In the last few years, accelerometer-based gait analysis systems fixed at different body locations have been proposed for ambulatory gait assessment and have been found valid and reliable for the analysis of gait parameters [7], [8], [9], [10], [11], [12], [13], [14], [15]. However, most body fixed accelerometer-based systems are still in need of further development in older adult populations [16].

A tri-axial accelerometer system (DynaPort^®MiniMod) placed on the lower trunk has previously been identified as a valid measure to detect differences in spatio-temporal gait parameters in children [13] and healthy, young adults [11], [12] for averaged step data. Based on a more conservative gait pattern characterised by a reduced trunk acceleration, walking speed and step length, that is often observed in older adults [15], [17], [18], [19], [20], it is not clear however, whether the application of this system in the elderly is valid.

The aim of this study was (1) to determine the concurrent validity of the DynaPort^®MiniMod system with the GAITRite^® system for spatio-temporal gait parameters 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.