Elsevier

Gait & Posture

Volume 33, Issue 2, February 2011, Pages 314-317
Gait & Posture

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Minimal detectable change for gait variables collected during treadmill walking in individuals post-stroke

https://doi.org/10.1016/j.gaitpost.2010.11.024Get rights and content

Abstract

Post-stroke gait impairments are common and result in slowed walking speeds and decreased community participation post-stroke. Treadmill training has recently emerged as an effective gait rehabilitation intervention. Furthermore, kinematic and kinetic data collected during treadmill walking are commonly used for assessing gait performance. The minimal detectable change (MDC) for gait variables provides a useful index to determine whether the magnitude of change in gait produced after an intervention is greater than the amount of change attributable to day-to-day variability in gait or test–retest measurement errors. The MDC values for kinematic, ground reaction force (GRF), spatial, and temporal variables collected during treadmill walking post-stroke have not been previously reported. The objective of this study was, therefore, to compute MDCs for post-stroke gait kinematics, GRF indices, temporal, and spatial measures during treadmill walking. Nineteen individuals with chronic post-stroke hemiparesis (12 males; age = 47–75 years; 72.6 ± 63.4 months since stroke) participated in 2 testing sessions separated by 20.7 ± 26.8 days. Our results showed that test–retest reliability was excellent for all gait variables tested (intraclass correlation coefficients = 0.799–0.986). MDCs were reported for hip, knee, and ankle joint angles (range 3.8° for trailing limb angles to 11.5° for hip extension), peak anterior GRF (2.85% body weight), mean vertical GRF (4.65% body weight), all temporal variables (range 3.2–4.2% gait cycle), and paretic step length (6.7 cm). These MDCs provide a useful reference to help interpret the magnitudes of changes in post-stroke gait variables.

Introduction

Treadmill training is commonly used for post-stroke gait rehabilitation [1], [2], [3]. To evaluate the efficacy of gait rehabilitation, it is critical to accurately measure post-stroke gait impairments before and after rehabilitation. Kinematic, ground reaction force (GRF), and spatiotemporal gait data provide a comprehensive assessment of gait deficits [4], [5], [6], [7]. An estimate of typical variability in gait data with repeated testing is helpful in determining if observed changes in gait are due to the intervention being investigated or simply measurement errors due to test–retest or day-to-day gait variability. The minimal detectable change (MDC) [8], [9] represents the amount of change in a variable necessary to conclude that the change is not attributable to error; it is the smallest change that falls outside the expected range of error and represents a “real” change [8], [9].

The reliability of kinematic and spatiotemporal data [5] and MDCs for GRF data [6] during overground walking has been previously reported for individuals post-stroke. A limitation in these studies was that the test and retest were conducted on the same day and therefore, did not account for day-to-day gait variability [5], [6]. Thus, application of these results when interpreting data from reports involving pre- and post-intervention testing is limited. Furthermore, despite the increasing use of treadmills for stroke rehabilitation [1], [2], [3] and for measuring gait [1], [2], [4], [10], MDCs for gait variables obtained during treadmill walking post-stroke have not been previously reported. The objective of the current study, therefore, was to determine MDCs for kinematic, GRF, temporal, and spatial gait variables during treadmill walking using data from repeated testing sessions in individuals with post-stroke gait impairments.

Section snippets

Methods

Nineteen individuals (12 males; age 47–75 years) with post-stroke hemiparesis (72.6 ± 63.4 months post-stroke) able to walk for >5 min were recruited (Table 1). Exclusion criteria included inability to follow commands and orthopedic or other neurologic conditions interfering with walking. All subjects signed consents approved by the Human Subject Review Board. Each subject participated in 2 sessions conducted on separate days (20.7 ± 26.8 days between sessions), with identical testing procedures.

Results

We reported MDC values (see Table 2) and demonstrated excellent between-session (ICCs range from 0.799 to 0.986) and within-session reliability (ICCs  0.9) for kinematic, spatio-temporal, and GRF data collected during treadmill walking in individuals post-stroke. Bland–Altman plots showed no systematic trends in the direction or distribution of test–retest errors for majority of variables (Fig. 2).

Discussion

We reported MDCs for post-stroke gait variables obtained via three-dimensional motion capture during treadmill walking. The between-session MDCs from our study account for test–retest errors in gait variables across 2 testing sessions caused by factors such as recalibrating the camera system, re-attaching reflective markers, and day-to-day gait variability. Between-session MDCs estimate the minimum change in gait that must be produced by an intervention for the change to be considered real;

Acknowledgements

Funding Sources: National Institutes of Nursing Research R01 grant NR010786 and Bioengineering Research partnership R01 grant HD038582 to Dr. Binder-Macleod; NIH K01 HD050582 to Dr. Reisman; NIH Shared Instrumentation Grant S10 RR022396-01 to Dr. Lynn Snyder-Mackler; DOD Grant W911NF-05-1-0097 to Dr. Irene Davis. The authors thank Ms. Margie Roos, PT, NCS for clinical testing and subject recruitment; Ms. Leigh Shrewsbury for scheduling and recruitment; Erin Helm for assistance with

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