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Test-retest reliability of temporal and spatial gait characteristics measured with an instrumented walkway system (GAITRite®)

Test-retest reliability of temporal and spatial gait characteristics measured with an... Background: The purpose of this study was to determine the test-retest reliability of temporal and spatial gait measurements over a one-week period as measured using an instrumented walkway system (GAITRite ). Methods: Subjects were tested on two occasions one week apart. Measurements were made at preferred and fast walking speeds using the GAITRite system. Measurements tested included walking speed, step length, stride length, base of support, step time, stride time, swing time, stance time, single and double support times, and toe in-toe out angle. Results: Twenty-one healthy subjects participated in this study. The group consisted of 12 men and 9 women, with an average age of 34 years (range: 19 – 59 years). At preferred walking speed, all gait measurements had ICC's of 0.92 and higher, except base of support which had an ICC of 0.80. At fast walking speed all gait measurements had ICC's above 0.89 except base of support (ICC = 0.79), Conclusions: Spatial-temporal gait measurements demonstrate good to excellent test-retest reliability over a one-week time span. expertise is needed. Such instrumentation is becoming Background Observational gait analysis is regularly performed by more common in the clinical environment, and quantita- physical therapists to determine treatment goals and is tive measures of gait are being used as outcome measures used as an evaluation tool during rehabilitation. How- to evaluate treatment efficacy and function [2]. However, ever, subjective gait analysis has only poor to moderate when using an objective gait assessment for the evaluation reliability and validity [1,2]. Objective assessments can of an intervention it is necessary to know if the detected supply the clinician with highly reliable and valid data, changes are genuine (that is, caused by the treatment) or but are usually time consuming, expensive, and they if they are caused by the instrumentation system's meas- demand specific expertise. Instrumented walkways, how- urement errors or normal variation of a person's gait. ever, can supply the clinician with quick objective meas- Therefore it is of great importance to have insight into urements of a patient's gait. In addition, no specific both reliability and validity of the instrument being used, Page 1 of 4 (page number not for citation purposes) BMC Musculoskeletal Disorders 2004, 5 http://www.biomedcentral.com/1471-2474/5/13 as well as the test-retest reliability of spatial – temporal puter based instrumented walkway that has been devel- gait measurements. oped to measure spatial and temporal gait characteristics. It includes a roll-up walkway available in various lengths Many instrumentation systems for quantitative gait anal- with embedded pressure sensors. The mat used for this ysis have been evaluated for reliability and validity. How- study is 6 m long with 18,432 pressure sensors. The walk- ever, test-retest reliability over time for spatial and way's active measurement area is 61 cm wide and 488 cm temporal gait measurements has not been studied to the long. Sensors are arranged in a grid pattern (48 × 384) and same extent. Bilney et al. [3] investigated the test-retest placed 1.27 cm on center. The sampling rate of the system reliability of spatial and temporal gait measurements used varies between 32.2 and 38.4 Hz. Data are uploaded using the GAITRite system between three consecutive to a computer, and automatic footstep identification and measurements on one day. They reported that the system parameter calculations are made. This system directly sup- was reliable for measuring temporal and spatial gait char- plies the clinician with quantitative information about the acteristics. However, until now no studies have been per- patient's gait. Studies have investigated the reliability and formed that investigated test-retest reliability with an validity of the GAITRite system for measuring spatial and interval of at least a week, using such a system. temporal gait characteristics. To validate the system's measurements, concurrent validity was assessed using a In the field of physical therapy, patients often are treated video-based analysis system, direct measures of chalk over periods lasting several weeks. If variability in normal footfall imprints, a stopwatch, and a footswitch system gait is significant from week to week, then measurements [3,5,6]. Cutlip et al. [5] reported the GAITRite system to of changes in gait can not be attributed to treatment be highly valid in measuring temporal characteristics, and effects. Since repeated evaluations of a person's gait in the McDonough et al. [6] and Bilney et al. [3] reported high clinic are routinely performed with intervals of several validity of the system on both spatial and temporal days or weeks, insight in this test-retest reliability over a measurements. longer period of time is essential. The consistency of gait has also been investigated by Urquhart et al. [4] who Procedure showed, using a computerized stride analyzer, that gait of Testing was performed in the gymnasium of the Depart- ment of Physical Therapy of the University Medical Center Parkinson's patients was stable over a seven-day interval. Nijmegen. The GAITRite mat was positioned in the gym The objective of this study was to determine the test-retest to allow the subject to begin walking 2 meters before the reliability of spatial and temporal gait measurements at mat, and to continue walking two meters past the end of preferred and fast walking speeds, as measured using an the mat without slowing. By starting before the mat and instrumented walkway (GAITRite ) over a one-week continuing past its end, we assured that the subject would period. We chose a population of healthy adults to be able be walking at his/her steady-state speed over the instru- to characterize the normal week-to-week variation one mented section of the mat. Each subject was instructed to would expect to see, without the confounding situation of walk at a self-selected comfortable speed. Data were col- improvement that one would see in a clinical population. lected for eight trials at the subject's self selected pace. This assured collection of at least eight right and eight left Methods strides. Eight strides has been shown to be appropriate for Subjects representing gait characteristics by mean values as repre- Twenty-one healthy subjects volunteered for this study. sentative of normal gait [7]. Subjects were free of any orthopedic disorder of the lower limb that might affect their gait, and did not report acute After completing these eight trials subjects were asked to pain or any other complaint likely to influence walking. walk the same distance at a self-selected higher speed. The group consisted of 12 men and 9 women, with a Eight trials were collected for this condition as well. Before mean age of 34 years (range: 19 – 59 years). This healthy data collection every subject practiced walking over the group was chosen as their gait would not be considered GAITRite mat in order to familiarize themselves with the likely to change clinically over a one-week period. All sub- test procedure. jects gave informed consent. This study protocol was ruled exempt from review by the Medical Ethics Board of the In order to assess the test-retest reliability of the spatial University Medical Center Nijmegen. and temporal gait measurements, each subject was evalu- ated again one week later. Subjects wore the same pair of Instrumentation: GAITRite shoes on both test days. In order to assess temporal-spatial characteristics we used the GAITRite system (SMS Technologies Ltd., Elizabeth The following eleven spatial and temporal gait measure- Way, Harlow Essex, UK). The GAITRite system is a com- ments were evaluated: Walking speed (cm/s), Step length Page 2 of 4 (page number not for citation purposes) BMC Musculoskeletal Disorders 2004, 5 http://www.biomedcentral.com/1471-2474/5/13 Table 1: Overview of spatial and temporal gait parameters during preferred and fast walking speeds for 21 subjects. Values represent means over the trial (standard deviation). Left and Right sides for unilateral parameters were treated separately. Preferred walking speed Fast walking speed Week 1 Week 2 Change Week 1 Week 2 Change Gait variables Mean (SD) Mean (SD) Mean (95% CI)* ICC (95% CI)* Mean (SD) Mean (SD) Mean (95% CI)* ICC (95% CI)* Walking speed (cm/s) 142.49 (19.58) 147.14 (20.32) 4.65 (1.27 – 8.03) 0.96 (0.91 – 0.99) 176.73 (17.11) 179.69 (15.98) 2.96 (-0.47 – 6.39) 0.95 (0.87 – 0.98) Step length (cm) 77.83 (8.48) 79.40 (8.30) 1.57 (0.68 – 2.46) 0.97 (0.95 – 0.98) 86.92 (8.04) 87.82 (7.43) 0.89 (0.13 – 1.66) 0.97 (0.95 – 0.99) Stride length (cm) 155.83 (17.09) 159.00 (16.62) 3.17 (1.36 – 4.98) 0.97 (0.94 – 0.98) 173.72 (15.96) 175.83 (14.74) 2.11 (0.49 – 3.74) 0.97 (0.95 – 0.98) Base of support (cm) 8.27 (1.82) 8.94 (1.83) 0.66 (0.19 – 1.14) 0.80 (0.50 – 0.92) 8.81 (1.94) 9.58 (1.88) 0.78 (0.27 – 1.29) 0.79 (0.47 – 0.91) Step time (s) 0.55 (0.034) 0.54 (0.036) -0.01 (-0.01 – -0.002) 0.95 (0.91 – 0.97) 0.50 (0.032) 0.49 (0.029) -0.01 (-0.01 – -0.002) 0.96 (0.92 – 0.98) Stride time (s) 1.10 (0.068) 1.09 (0.071) -0.01 (-0.02 – -0.003) 0.96 (0.92 – 0.98) 0.99 (0.066) 0.98 (0.056) -0.01 (-0.02 – -0.001) 0.96 (0.92 – 0.98) Swing time (s) 0.45 (0.025) 0.44 (0.022) -0.01 (-0.01 – -0.003) 0.93 (0.87 – 0.96) 0.41 (0.024) 0.41 (0.019) -0.01 (-0.01 – -0.001) 0.89 (0.80 – 0.94) Stance time (s) 0.65 (0.050) 0.65 (0.053) -0.01 (-0.01 – 0.002) 0.94 (0.89 – 0.97) 0.57 (0.047) 0.57 (0.042) -0.002 (-0.01 – 0.001) 0.95 (0.90 – 0.97) Single support time (s) 0.45 (0.026) 0.44 (0.022) -0.01 (-0.01 – -0.002) 0.92 (0.84 – 0.95) 0.41 (0.025) 0.41 (0.019) -0.001 (-0.01 – -0.001) 0.89 (0.80 – 0.94) Double support time (s) 0.21 (0.040) 0.21 (0.037) < 0.001 (-0.01 – 0.01) 0.93 (0.87 – 0.96) 0.17 (0.028) 0.17 (0.031) -0.001 (-0.01 – 0.004) 0.91 (0.83 – 0.95) Toe in toe out (deg) 5.09 (5.83) 5.28 (5.74) 0.20 (-0.30 – 0.70) 0.98 (0.96 – 0.99) 4.69 (6.07) 4.70 (5.74) -0.02 (-0.56 – 0.59) 0.98 (0.95 – 0.99) * 95% CI = 95% Confidence Interval (cm), Stride length (cm), Base of support (cm), Step time Test-retest reliability at fast walking speed (s), Stride time (s), Swing time (s), Stance time (s), Single Fast walking speed also proved to be highly reproducible support time (s), Double support time (s), and Toe in toe (ICC = 0.95). The base of support during fast walking had out (deg). the lowest ICC (0.79). Swing time and single support time each had ICC's of 0.89. ICC's for all other gait measure- Data analysis ments were 0.91 and higher. Footsteps which did not fall entirely on the GAITRite mat were deleted. Mean values for each gait parameter were Differences in gait measurements between week 1 and 2 calculated using the first ten complete steps derived from Change scores in Table 1 show several of the gait measure- the eight trials at each speed: self-selected pace and fast ments to have increased or decreased. We believe that this walking speed. Data for individual steps were averaged, is more an artifact of the statistical analysis than it is an not averages for each trial, to avoid situations where one indication of change from Week 1 to Week 2. As within- trial had more complete steps than another. Mean values week variability of certain of these parameters is very low, were used as this is common practice when evaluating small changes between-week may present as 'statistically these measurements in the clinic. significant'. However, we do not consider these small changes clinically relevant in most cases. Statistics To determine test-retest reliability, intraclass correlation Discussion coefficients (ICC) were used (Model 2, k) [8]. Although It is essential that any measurements used for evaluation the 3, k model is often used in intrarater and test-retest of an intervention are not subject to significant intra-indi- reliability studies, we chose the 2, k model because this vidual variability over time. While instrumentation is statistical technique is more conservative and therefore often evaluated for reliability and validity, this alone is more generalizable [8]. not enough. When evaluating an intervention one must be able to rely on the fact that observed changes are genu- ine and not caused by normal variation in task perform- Results Test-retest reliability at preferred walking speed ance. Therefore it is important to investigate the test-retest At preferred walking speed, ICC's for all gait measure- reliability over time of performance measures that are ments tested were 0.92 and higher, with the exception of used as diagnostic tools or to evaluate interventions. base of support, which had an ICC of 0.80 (see Table 1). Preferred walking speed also proved to be highly repro- In this study we used ICC's to evaluate test-retest reliabil- ducible (ICC = 0.96). ity. A major advantage of ICC analysis over standard cor- relation analysis is that the ICC also accounts for differences between the data sets by using analysis of var- iance between and within data sets [8]. Page 3 of 4 (page number not for citation purposes) BMC Musculoskeletal Disorders 2004, 5 http://www.biomedcentral.com/1471-2474/5/13 8. Portney LG, Watkins MP: Foundations of clinical research: Almost all of the gait measurements tested at preferred applications to practice. Upper Saddle River, NJ, Prentice-Hall, and fast walking speeds had ICC's above 0.90. Portney Inc; 2000. and Watkins have indicated that clinical measurements should show reliability of at least 0.90 [8]. Only the base Pre-publication history of support showed somewhat lower test-retest reliability at The pre-publication history for this paper can be accessed both the preferred and fast walking speed. From previous here: studies using the GAITRite system, we suspect that this lower reliability is a result of the spatial resolution of the http://www.biomedcentral.com/1471-2474/5/13/prepub instrumentation, and not increased normal variation in walking patterns week-to-week [7]. In conclusion, all spatial and temporal gait measurements investigated in this study demonstrated good to excellent test-retest reliability in an adult population without pathology. Thus, changes in gait observed after treatment can likely be attributed to that treatment, and not to test- retest variability. This makes the GAITRite a good instru- ment to evaluate treatment effects using spatial and tem- poral gait measurements. Some caution might be appropriate for considering changes in base of support as measured using the GAITRite system. Future research should address natural changes or variability over time of spatial and temporal gait measurements in pediatric and geriatric populations, as well as populations with specific pathologies. Authors' contributions CU participated in the study design, supervised the data collection, and performed statistical analysis. MB partici- pated in the study design. Both authors contributed equally to the final manuscript and approve its content. Acknowledgements We would like to thank Amy Swing, PT, MS and John Noone, PT, MS for assisting during the experiments. At the time of the experiment they were physical therapy students at Thomas Jefferson University (Philadelphia, USA), participating in an international research internship with the Univer- sity Medical Center Nijmegen (The Netherlands). References 1. Krebs DE, Edelstein JE, Fishman S: Reliability of observational kin- ematic gait analysis. Phys Ther 1985, 65:1027-1033. 2. Coutts F: Gait analysis in the therapeutic environment. Man Ther 1999, 4:2-10. 3. Bilney B, Morris M, Webster K: Concurrent related validity of the GAITRite walkway system for quantification of the spa- Publish with Bio Med Central and every tial and temporal parameters of gait. Gait Posture 2003, 17:68-74. scientist can read your work free of charge 4. Urquhart DM, Morris ME, Iansek R: Gait consistency over a 7-day "BioMed Central will be the most significant development for interval in people with Parkinson's disease. Arch Phys Med Rehabil 1999, 80:696-701. disseminating the results of biomedical researc h in our lifetime." 5. Cutlip RG, Mancinelli C, Huber F, DiPasquale J: Evaluation of an Sir Paul Nurse, Cancer Research UK instrumented walkway for measurement of the kinematic parameters of gait. Gait Posture 2000, 12:134-138. Your research papers will be: 6. McDonough AL, Batavia M, Chen FC, Kwon S, Ziai J: The validity available free of charge to the entire biomedical community and reliability of the GAITRite system's measurements: A peer reviewed and published immediately upon acceptance preliminary evaluation. Arch Phys Med Rehabil 2001, 82:419-425. 7. Besser MP, Kmieczak K, Schwartz L, Snyderman M, Wasko J, Selby- cited in PubMed and archived on PubMed Central Silverstein L: Reliability of temporal spatial gait parameters yours — you keep the copyright means in adults without imparment. Annual Meeting of the Gait and Clinical Movement Analysis Society Dallas, Texas, Gait Posture; BioMedcentral Submit your manuscript here: 1999:9(2): 113. http://www.biomedcentral.com/info/publishing_adv.asp Page 4 of 4 (page number not for citation purposes) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png BMC Musculoskeletal Disorders Springer Journals

Test-retest reliability of temporal and spatial gait characteristics measured with an instrumented walkway system (GAITRite®)

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Springer Journals
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Copyright © 2004 by van Uden and Besser; licensee BioMed Central Ltd.
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Medicine & Public Health; Orthopedics; Rehabilitation; Rheumatology; Sports Medicine; Internal Medicine; Epidemiology
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Abstract

Background: The purpose of this study was to determine the test-retest reliability of temporal and spatial gait measurements over a one-week period as measured using an instrumented walkway system (GAITRite ). Methods: Subjects were tested on two occasions one week apart. Measurements were made at preferred and fast walking speeds using the GAITRite system. Measurements tested included walking speed, step length, stride length, base of support, step time, stride time, swing time, stance time, single and double support times, and toe in-toe out angle. Results: Twenty-one healthy subjects participated in this study. The group consisted of 12 men and 9 women, with an average age of 34 years (range: 19 – 59 years). At preferred walking speed, all gait measurements had ICC's of 0.92 and higher, except base of support which had an ICC of 0.80. At fast walking speed all gait measurements had ICC's above 0.89 except base of support (ICC = 0.79), Conclusions: Spatial-temporal gait measurements demonstrate good to excellent test-retest reliability over a one-week time span. expertise is needed. Such instrumentation is becoming Background Observational gait analysis is regularly performed by more common in the clinical environment, and quantita- physical therapists to determine treatment goals and is tive measures of gait are being used as outcome measures used as an evaluation tool during rehabilitation. How- to evaluate treatment efficacy and function [2]. However, ever, subjective gait analysis has only poor to moderate when using an objective gait assessment for the evaluation reliability and validity [1,2]. Objective assessments can of an intervention it is necessary to know if the detected supply the clinician with highly reliable and valid data, changes are genuine (that is, caused by the treatment) or but are usually time consuming, expensive, and they if they are caused by the instrumentation system's meas- demand specific expertise. Instrumented walkways, how- urement errors or normal variation of a person's gait. ever, can supply the clinician with quick objective meas- Therefore it is of great importance to have insight into urements of a patient's gait. In addition, no specific both reliability and validity of the instrument being used, Page 1 of 4 (page number not for citation purposes) BMC Musculoskeletal Disorders 2004, 5 http://www.biomedcentral.com/1471-2474/5/13 as well as the test-retest reliability of spatial – temporal puter based instrumented walkway that has been devel- gait measurements. oped to measure spatial and temporal gait characteristics. It includes a roll-up walkway available in various lengths Many instrumentation systems for quantitative gait anal- with embedded pressure sensors. The mat used for this ysis have been evaluated for reliability and validity. How- study is 6 m long with 18,432 pressure sensors. The walk- ever, test-retest reliability over time for spatial and way's active measurement area is 61 cm wide and 488 cm temporal gait measurements has not been studied to the long. Sensors are arranged in a grid pattern (48 × 384) and same extent. Bilney et al. [3] investigated the test-retest placed 1.27 cm on center. The sampling rate of the system reliability of spatial and temporal gait measurements used varies between 32.2 and 38.4 Hz. Data are uploaded using the GAITRite system between three consecutive to a computer, and automatic footstep identification and measurements on one day. They reported that the system parameter calculations are made. This system directly sup- was reliable for measuring temporal and spatial gait char- plies the clinician with quantitative information about the acteristics. However, until now no studies have been per- patient's gait. Studies have investigated the reliability and formed that investigated test-retest reliability with an validity of the GAITRite system for measuring spatial and interval of at least a week, using such a system. temporal gait characteristics. To validate the system's measurements, concurrent validity was assessed using a In the field of physical therapy, patients often are treated video-based analysis system, direct measures of chalk over periods lasting several weeks. If variability in normal footfall imprints, a stopwatch, and a footswitch system gait is significant from week to week, then measurements [3,5,6]. Cutlip et al. [5] reported the GAITRite system to of changes in gait can not be attributed to treatment be highly valid in measuring temporal characteristics, and effects. Since repeated evaluations of a person's gait in the McDonough et al. [6] and Bilney et al. [3] reported high clinic are routinely performed with intervals of several validity of the system on both spatial and temporal days or weeks, insight in this test-retest reliability over a measurements. longer period of time is essential. The consistency of gait has also been investigated by Urquhart et al. [4] who Procedure showed, using a computerized stride analyzer, that gait of Testing was performed in the gymnasium of the Depart- ment of Physical Therapy of the University Medical Center Parkinson's patients was stable over a seven-day interval. Nijmegen. The GAITRite mat was positioned in the gym The objective of this study was to determine the test-retest to allow the subject to begin walking 2 meters before the reliability of spatial and temporal gait measurements at mat, and to continue walking two meters past the end of preferred and fast walking speeds, as measured using an the mat without slowing. By starting before the mat and instrumented walkway (GAITRite ) over a one-week continuing past its end, we assured that the subject would period. We chose a population of healthy adults to be able be walking at his/her steady-state speed over the instru- to characterize the normal week-to-week variation one mented section of the mat. Each subject was instructed to would expect to see, without the confounding situation of walk at a self-selected comfortable speed. Data were col- improvement that one would see in a clinical population. lected for eight trials at the subject's self selected pace. This assured collection of at least eight right and eight left Methods strides. Eight strides has been shown to be appropriate for Subjects representing gait characteristics by mean values as repre- Twenty-one healthy subjects volunteered for this study. sentative of normal gait [7]. Subjects were free of any orthopedic disorder of the lower limb that might affect their gait, and did not report acute After completing these eight trials subjects were asked to pain or any other complaint likely to influence walking. walk the same distance at a self-selected higher speed. The group consisted of 12 men and 9 women, with a Eight trials were collected for this condition as well. Before mean age of 34 years (range: 19 – 59 years). This healthy data collection every subject practiced walking over the group was chosen as their gait would not be considered GAITRite mat in order to familiarize themselves with the likely to change clinically over a one-week period. All sub- test procedure. jects gave informed consent. This study protocol was ruled exempt from review by the Medical Ethics Board of the In order to assess the test-retest reliability of the spatial University Medical Center Nijmegen. and temporal gait measurements, each subject was evalu- ated again one week later. Subjects wore the same pair of Instrumentation: GAITRite shoes on both test days. In order to assess temporal-spatial characteristics we used the GAITRite system (SMS Technologies Ltd., Elizabeth The following eleven spatial and temporal gait measure- Way, Harlow Essex, UK). The GAITRite system is a com- ments were evaluated: Walking speed (cm/s), Step length Page 2 of 4 (page number not for citation purposes) BMC Musculoskeletal Disorders 2004, 5 http://www.biomedcentral.com/1471-2474/5/13 Table 1: Overview of spatial and temporal gait parameters during preferred and fast walking speeds for 21 subjects. Values represent means over the trial (standard deviation). Left and Right sides for unilateral parameters were treated separately. Preferred walking speed Fast walking speed Week 1 Week 2 Change Week 1 Week 2 Change Gait variables Mean (SD) Mean (SD) Mean (95% CI)* ICC (95% CI)* Mean (SD) Mean (SD) Mean (95% CI)* ICC (95% CI)* Walking speed (cm/s) 142.49 (19.58) 147.14 (20.32) 4.65 (1.27 – 8.03) 0.96 (0.91 – 0.99) 176.73 (17.11) 179.69 (15.98) 2.96 (-0.47 – 6.39) 0.95 (0.87 – 0.98) Step length (cm) 77.83 (8.48) 79.40 (8.30) 1.57 (0.68 – 2.46) 0.97 (0.95 – 0.98) 86.92 (8.04) 87.82 (7.43) 0.89 (0.13 – 1.66) 0.97 (0.95 – 0.99) Stride length (cm) 155.83 (17.09) 159.00 (16.62) 3.17 (1.36 – 4.98) 0.97 (0.94 – 0.98) 173.72 (15.96) 175.83 (14.74) 2.11 (0.49 – 3.74) 0.97 (0.95 – 0.98) Base of support (cm) 8.27 (1.82) 8.94 (1.83) 0.66 (0.19 – 1.14) 0.80 (0.50 – 0.92) 8.81 (1.94) 9.58 (1.88) 0.78 (0.27 – 1.29) 0.79 (0.47 – 0.91) Step time (s) 0.55 (0.034) 0.54 (0.036) -0.01 (-0.01 – -0.002) 0.95 (0.91 – 0.97) 0.50 (0.032) 0.49 (0.029) -0.01 (-0.01 – -0.002) 0.96 (0.92 – 0.98) Stride time (s) 1.10 (0.068) 1.09 (0.071) -0.01 (-0.02 – -0.003) 0.96 (0.92 – 0.98) 0.99 (0.066) 0.98 (0.056) -0.01 (-0.02 – -0.001) 0.96 (0.92 – 0.98) Swing time (s) 0.45 (0.025) 0.44 (0.022) -0.01 (-0.01 – -0.003) 0.93 (0.87 – 0.96) 0.41 (0.024) 0.41 (0.019) -0.01 (-0.01 – -0.001) 0.89 (0.80 – 0.94) Stance time (s) 0.65 (0.050) 0.65 (0.053) -0.01 (-0.01 – 0.002) 0.94 (0.89 – 0.97) 0.57 (0.047) 0.57 (0.042) -0.002 (-0.01 – 0.001) 0.95 (0.90 – 0.97) Single support time (s) 0.45 (0.026) 0.44 (0.022) -0.01 (-0.01 – -0.002) 0.92 (0.84 – 0.95) 0.41 (0.025) 0.41 (0.019) -0.001 (-0.01 – -0.001) 0.89 (0.80 – 0.94) Double support time (s) 0.21 (0.040) 0.21 (0.037) < 0.001 (-0.01 – 0.01) 0.93 (0.87 – 0.96) 0.17 (0.028) 0.17 (0.031) -0.001 (-0.01 – 0.004) 0.91 (0.83 – 0.95) Toe in toe out (deg) 5.09 (5.83) 5.28 (5.74) 0.20 (-0.30 – 0.70) 0.98 (0.96 – 0.99) 4.69 (6.07) 4.70 (5.74) -0.02 (-0.56 – 0.59) 0.98 (0.95 – 0.99) * 95% CI = 95% Confidence Interval (cm), Stride length (cm), Base of support (cm), Step time Test-retest reliability at fast walking speed (s), Stride time (s), Swing time (s), Stance time (s), Single Fast walking speed also proved to be highly reproducible support time (s), Double support time (s), and Toe in toe (ICC = 0.95). The base of support during fast walking had out (deg). the lowest ICC (0.79). Swing time and single support time each had ICC's of 0.89. ICC's for all other gait measure- Data analysis ments were 0.91 and higher. Footsteps which did not fall entirely on the GAITRite mat were deleted. Mean values for each gait parameter were Differences in gait measurements between week 1 and 2 calculated using the first ten complete steps derived from Change scores in Table 1 show several of the gait measure- the eight trials at each speed: self-selected pace and fast ments to have increased or decreased. We believe that this walking speed. Data for individual steps were averaged, is more an artifact of the statistical analysis than it is an not averages for each trial, to avoid situations where one indication of change from Week 1 to Week 2. As within- trial had more complete steps than another. Mean values week variability of certain of these parameters is very low, were used as this is common practice when evaluating small changes between-week may present as 'statistically these measurements in the clinic. significant'. However, we do not consider these small changes clinically relevant in most cases. Statistics To determine test-retest reliability, intraclass correlation Discussion coefficients (ICC) were used (Model 2, k) [8]. Although It is essential that any measurements used for evaluation the 3, k model is often used in intrarater and test-retest of an intervention are not subject to significant intra-indi- reliability studies, we chose the 2, k model because this vidual variability over time. While instrumentation is statistical technique is more conservative and therefore often evaluated for reliability and validity, this alone is more generalizable [8]. not enough. When evaluating an intervention one must be able to rely on the fact that observed changes are genu- ine and not caused by normal variation in task perform- Results Test-retest reliability at preferred walking speed ance. Therefore it is important to investigate the test-retest At preferred walking speed, ICC's for all gait measure- reliability over time of performance measures that are ments tested were 0.92 and higher, with the exception of used as diagnostic tools or to evaluate interventions. base of support, which had an ICC of 0.80 (see Table 1). Preferred walking speed also proved to be highly repro- In this study we used ICC's to evaluate test-retest reliabil- ducible (ICC = 0.96). ity. A major advantage of ICC analysis over standard cor- relation analysis is that the ICC also accounts for differences between the data sets by using analysis of var- iance between and within data sets [8]. Page 3 of 4 (page number not for citation purposes) BMC Musculoskeletal Disorders 2004, 5 http://www.biomedcentral.com/1471-2474/5/13 8. Portney LG, Watkins MP: Foundations of clinical research: Almost all of the gait measurements tested at preferred applications to practice. Upper Saddle River, NJ, Prentice-Hall, and fast walking speeds had ICC's above 0.90. Portney Inc; 2000. and Watkins have indicated that clinical measurements should show reliability of at least 0.90 [8]. Only the base Pre-publication history of support showed somewhat lower test-retest reliability at The pre-publication history for this paper can be accessed both the preferred and fast walking speed. From previous here: studies using the GAITRite system, we suspect that this lower reliability is a result of the spatial resolution of the http://www.biomedcentral.com/1471-2474/5/13/prepub instrumentation, and not increased normal variation in walking patterns week-to-week [7]. In conclusion, all spatial and temporal gait measurements investigated in this study demonstrated good to excellent test-retest reliability in an adult population without pathology. Thus, changes in gait observed after treatment can likely be attributed to that treatment, and not to test- retest variability. This makes the GAITRite a good instru- ment to evaluate treatment effects using spatial and tem- poral gait measurements. Some caution might be appropriate for considering changes in base of support as measured using the GAITRite system. Future research should address natural changes or variability over time of spatial and temporal gait measurements in pediatric and geriatric populations, as well as populations with specific pathologies. Authors' contributions CU participated in the study design, supervised the data collection, and performed statistical analysis. MB partici- pated in the study design. Both authors contributed equally to the final manuscript and approve its content. Acknowledgements We would like to thank Amy Swing, PT, MS and John Noone, PT, MS for assisting during the experiments. At the time of the experiment they were physical therapy students at Thomas Jefferson University (Philadelphia, USA), participating in an international research internship with the Univer- sity Medical Center Nijmegen (The Netherlands). References 1. Krebs DE, Edelstein JE, Fishman S: Reliability of observational kin- ematic gait analysis. Phys Ther 1985, 65:1027-1033. 2. Coutts F: Gait analysis in the therapeutic environment. Man Ther 1999, 4:2-10. 3. Bilney B, Morris M, Webster K: Concurrent related validity of the GAITRite walkway system for quantification of the spa- Publish with Bio Med Central and every tial and temporal parameters of gait. Gait Posture 2003, 17:68-74. scientist can read your work free of charge 4. Urquhart DM, Morris ME, Iansek R: Gait consistency over a 7-day "BioMed Central will be the most significant development for interval in people with Parkinson's disease. Arch Phys Med Rehabil 1999, 80:696-701. disseminating the results of biomedical researc h in our lifetime." 5. Cutlip RG, Mancinelli C, Huber F, DiPasquale J: Evaluation of an Sir Paul Nurse, Cancer Research UK instrumented walkway for measurement of the kinematic parameters of gait. Gait Posture 2000, 12:134-138. Your research papers will be: 6. McDonough AL, Batavia M, Chen FC, Kwon S, Ziai J: The validity available free of charge to the entire biomedical community and reliability of the GAITRite system's measurements: A peer reviewed and published immediately upon acceptance preliminary evaluation. Arch Phys Med Rehabil 2001, 82:419-425. 7. Besser MP, Kmieczak K, Schwartz L, Snyderman M, Wasko J, Selby- cited in PubMed and archived on PubMed Central Silverstein L: Reliability of temporal spatial gait parameters yours — you keep the copyright means in adults without imparment. Annual Meeting of the Gait and Clinical Movement Analysis Society Dallas, Texas, Gait Posture; BioMedcentral Submit your manuscript here: 1999:9(2): 113. http://www.biomedcentral.com/info/publishing_adv.asp Page 4 of 4 (page number not for citation purposes)

Journal

BMC Musculoskeletal Disorders – Springer Journals

Published: May 17, 2004

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