Kelly J. Bower

Concurrent validity of the Microsoft Kinect for assessment of spatiotemporal gait variables

Spatiotemporal characteristics of gait such as step time and length are often associated with overall physical function in clinical populations, but can be difficult, time consuming and obtrusive to measure. This study assessed the concurrent validity of overground walking spatiotemporal data recorded using a criterion reference - a marker-based three-dimensional motion analysis (3DMA) system - and a low-cost, markerless alternative, the automated skeleton tracking output from the Microsoft Kinect™ (Kinect). Twenty-one healthy adults performed normal walking trials while being monitored using both systems. The outcome measures of gait speed, step length and time, stride length and time and peak foot swing velocity were derived using supervised automated analysis. To assess the agreement between the Kinect and 3DMA devices, Bland-Altman 95% bias and limits of agreement, percentage error, relative agreement (Pearsons correlation coefficients: r) overall agreement (concordance correlation coefficients: rc) and landmark location linearity as a function of distance from the sensor were determined. Gait speed, step length and stride length from the two devices possessed excellent agreement (r and rc values >0.90). Foot swing velocity possessed excellent relative (r=0.93) but only modest overall (rc=0.54) agreement. Step time (r=0.82 and rc=0.23) and stride time (r=0.69 and rc=0.14) possessed excellent and modest relative agreement respectively but poor overall agreement. Landmark location linearity was excellent (R(2)=0.991). This widely available, low-cost and portable system could provide clinicians with significant advantages for assessing some spatiotemporal gait parameters. However, caution must be taken when choosing outcome variables as some commonly reported variables cannot be accurately measured.

Reliability and concurrent validity of the Microsoft Xbox One Kinect for assessment of standing balance and postural control

The Microsoft Kinect V2 for Windows, also known as the Xbox One Kinect, includes new and potentially far improved depth and image sensors which may increase its accuracy for assessing postural control and balance. The aim of this study was to assess the concurrent validity and reliability of kinematic data recorded using a marker-based three dimensional motion analysis (3DMA) system and the Kinect V2 during a variety of static and dynamic balance assessments. Thirty healthy adults performed two sessions, separated by one week, consisting of static standing balance tests under different visual (eyes open vs. closed) and supportive (single limb vs. double limb) conditions, and dynamic balance tests consisting of forward and lateral reach and an assessment of limits of stability. Marker coordinate and joint angle data were concurrently recorded using the Kinect V2 skeletal tracking algorithm and the 3DMA system. Task-specific outcome measures from each system on Day 1 and 2 were compared. Concurrent validity of trunk angle data during the dynamic tasks and anterior-posterior range and path length in the static balance tasks was excellent (Pearsons r>0.75). In contrast, concurrent validity for medial-lateral range and path length was poor to modest for all trials except single leg eyes closed balance. Within device test-retest reliability was variable; however, the results were generally comparable between devices. In conclusion, the Kinect V2 has the potential to be used as a reliable and valid tool for the assessment of some aspects of balance performance.

Gait assessment using the Microsoft Xbox One Kinect: Concurrent validity and inter-day reliability of spatiotemporal and kinematic variables.

The revised Xbox One Kinect, also known as the Microsoft Kinect V2 for Windows, includes enhanced hardware which may improve its utility as a gait assessment tool. This study examined the concurrent validity and inter-day reliability of spatiotemporal and kinematic gait parameters estimated using the Kinect V2 automated body tracking system and a criterion reference three-dimensional motion analysis (3DMA) marker-based camera system. Thirty healthy adults performed two testing sessions consisting of comfortable and fast paced walking trials. Spatiotemporal outcome measures related to gait speed, speed variability, step length, width and time, foot swing velocity and medial-lateral and vertical pelvis displacement were examined. Kinematic outcome measures including ankle flexion, knee flexion and adduction and hip flexion were examined. To assess the agreement between Kinect and 3DMA systems, Bland-Altman plots, relative agreement (Pearsons correlation) and overall agreement (concordance correlation coefficients) were determined. Reliability was assessed using intraclass correlation coefficients, Cronbachs alpha and standard error of measurement. The spatiotemporal measurements had consistently excellent (r≥0.75) concurrent validity, with the exception of modest validity for medial-lateral pelvis sway (r=0.45-0.46) and fast paced gait speed variability (r=0.73). In contrast kinematic validity was consistently poor to modest, with all associations between the systems weak (r<0.50). In those measures with acceptable validity, the inter-day reliability was similar between systems. In conclusion, while the Kinect V2 body tracking may not accurately obtain lower body kinematic data, it shows great potential as a tool for measuring spatiotemporal aspects of gait.

Clinical feasibility of the Nintendo Wii™ for balance training post-stroke: a phase II randomized controlled trial in an inpatient setting:

Objective: To investigate the feasibility and potential efficacy of the Nintendo Wii™ for balance rehabilitation after stroke. Design: Phase II, single-blind, randomized controlled trial. Setting: Inpatient rehabilitation facility. Subjects: Thirty adults (mean age 63.6 (14.7) years) undergoing inpatient rehabilitation who were less than three months post-stroke and able to stand unsupported. Interventions: Participants were allocated to a Balance Group, using the ‘Wii Fit Plus’ in standing, or Upper Limb Group, using the ‘Wii Sports/Sports Resort’ in sitting. Both groups undertook three 45 minute sessions per week over two to four weeks in addition to standard care. Main measures: The primary focus was feasibility, addressed by recruitment, retention, adherence, acceptability and safety. Efficacy was evaluated by balance, mobility and upper limb outcomes. Results: Twenty-one percent of individuals screened were recruited and 86% (n = 30) of eligible people agreed to participate. Study retention and session adherence was 90% and > 99%, respectively, at two weeks; dropping to 70% and 87% at four weeks due to early discharge. All participants reported enjoying the sessions and most felt they were beneficial. No major adverse events occurred. Wii use by the Balance Group was associated with trends for improved balance, with significantly greater improvement in outcomes including the Step Test and Wii Balance Board-derived centre of pressure scores. The Upper Limb Group had larger, non-significant changes in arm function. Conclusions: A Wii-based approach appears feasible and promising for post-stroke balance rehabilitation. A larger randomized controlled trial is recommended to further investigate efficacy.

Assessment of Lower Limb Muscle Strength and Power Using Hand-Held and Fixed Dynamometry: A Reliability and Validity Study

Introduction Hand-held dynamometry (HHD) has never previously been used to examine isometric muscle power. Rate of force development (RFD) is often used for muscle power assessment, however no consensus currently exists on the most appropriate method of calculation. The aim of this study was to examine the reliability of different algorithms for RFD calculation and to examine the intra-rater, inter-rater, and inter-device reliability of HHD as well as the concurrent validity of HHD for the assessment of isometric lower limb muscle strength and power. Methods 30 healthy young adults (age: 23±5yrs, male: 15) were assessed on two sessions. Isometric muscle strength and power were measured using peak force and RFD respectively using two HHDs (Lafayette Model-01165 and Hoggan microFET2) and a criterion-reference KinCom dynamometer. Statistical analysis of reliability and validity comprised intraclass correlation coefficients (ICC), Pearson correlations, concordance correlations, standard error of measurement, and minimal detectable change. Results Comparison of RFD methods revealed that a peak 200ms moving window algorithm provided optimal reliability results. Intra-rater, inter-rater, and inter-device reliability analysis of peak force and RFD revealed mostly good to excellent reliability (coefficients ≥ 0.70) for all muscle groups. Concurrent validity analysis showed moderate to excellent relationships between HHD and fixed dynamometry for the hip and knee (ICCs ≥ 0.70) for both peak force and RFD, with mostly poor to good results shown for the ankle muscles (ICCs = 0.31–0.79). Conclusions Hand-held dynamometry has good to excellent reliability and validity for most measures of isometric lower limb strength and power in a healthy population, particularly for proximal muscle groups. To aid implementation we have created freely available software to extract these variables from data stored on the Lafayette device. Future research should examine the reliability and validity of these variables in clinical populations.

Quantifying Individual Components of the Timed Up and Go Using the Kinect in People Living With Stroke

Background. The Microsoft Kinect presents a simple, inexpensive, and portable method of examining the independent components of the Timed Up and Go (TUG) without any intrusion on the patient. Objective. This study examined the reliability of these measures, and whether they improved prediction of performance on common clinical tests. Methods. Thirty individuals with stroke completed 4 clinical assessments, including the TUG, 10-m walk test (10MWT), Step Test, and Functional Reach test on 2 testing occasions. The TUG was assessed using the Kinect to determine 7 different functional components. Test–retest reliability was assessed using intraclass correlation coefficient (ICC), redundancy using Spearman’s correlation, and score prediction on the clinical tests using multiple regression. Results. All Kinect-TUG variables possessed excellent reliability (ICC(2,k) > 0.90) except trunk flexion angle (ICC = 0.73). Trunk flexion angle and first step length were nonredundant with total TUG time. When predicting 10MWT and Step Test scores, adding step length into regression models comprising age and total TUG time improved model performance by 7% (P <.01) and 6% (P =.03), respectively. Specifically, an interquartile range increase in first step length (0.19 m) was associated with a 0.15 m/s faster gait speed and 1.8 more repetitions on the Step Test. These effect sizes were comparable to our minimal detectable change scores of 0.17 m/s for gait speed and 1.71 repetitions for the Step Test. Conclusions. Using the Kinect to independently assess the multiple components of the TUG may provide reliable and clinically useful information. This could enable efficient and information-rich large-scale assessments of physical deficits following stroke.

Instrumented Static and Dynamic Balance Assessment after Stroke Using Wii Balance Boards: Reliability and Association with Clinical Tests

Background and Objectives The Wii Balance Board (WBB) is a globally accessible device that shows promise as a clinically useful balance assessment tool. Although the WBB has been found to be comparable to a laboratory-grade force platform for obtaining centre of pressure data, it has not been comprehensively studied in clinical populations. The aim of this study was to investigate the measurement properties of tests utilising the WBB in people after stroke. Methods Thirty individuals who were more than three months post-stroke and able to stand unsupported were recruited from a single outpatient rehabilitation facility. Participants performed standardised assessments incorporating the WBB and customised software (static stance with eyes open and closed, static weight-bearing asymmetry, dynamic mediolateral weight shifting and dynamic sit-to-stand) in addition to commonly employed clinical tests (10 Metre Walk Test, Timed Up and Go, Step Test and Functional Reach) on two testing occasions one week apart. Test-retest reliability and construct validity of the WBB tests were investigated. Results All WBB-based outcomes were found to be highly reliable between testing occasions (ICC  = 0.82 to 0.98). Correlations were poor to moderate between WBB variables and clinical tests, with the strongest associations observed between task-related activities, such as WBB mediolateral weight shifting and the Step Test. Conclusions The WBB, used with customised software, is a reliable and potentially useful tool for the assessment of balance and weight-bearing asymmetry following stroke. Future research is recommended to further investigate validity and responsiveness.

Effective Feedback Procedures in Games for Health.

Feedback on game performance can be provided in many ways (e.g., cumulative points on game achievements, points on selected aspects of game play, biofeedback, brief statements offered during gameplay on choices made, verbal feedback at end of gameplay on overall performance, etc.). Feedback could be used motivationally to maintain player interest and involvement, informationally to guide the player in more effective choices, to build player confidence, and for a variety of other purposes. Although diverse feedback types and purposes are possible, some are more likely to be useful and effective. We have contacted several accomplished game designers and game researchers to obtain their insights into issues in feedback in Games for Health Journal.

Associations between lower limb strength and gait velocity following stroke: a systematic review.

Abstract Objective: The aim of this systematic review was to identify literature examining associations between isometric strength and gait velocity following stroke. Methods: An electronic search was performed using six online databases. Targeted searching of reference lists of included articles and three relevant journals was also performed. Two independent reviewers identified relevant articles, extracted data and assessed the methodological quality of included articles. Inclusion criteria involved studies that assessed univariate correlations between gait velocity and isometric strength of individual lower limb muscle groups in a stroke population. Results: Twenty-one studies were included for review. The majority of included studies had a relatively small sample size. After accounting for sample size and methodological quality, the knee extensors showed poor-to-moderate correlations with gait velocity while the ankle dorsiflexors showed the strongest association with gait velocity. Conclusions: Current evidence suggests that the strength of the ankle dorsiflexors has a stronger correlation to gait velocity compared with other lower limb muscle groups. Consequently, a focus on increasing ankle dorsiflexor strength to improve gait velocity following stroke may be beneficial. However, due to limitations of the research identified, further research is needed to determine the associations between lower limb strength and gait velocity following stroke.

Reliability and validity of the Wii Balance Board for assessment of standing balance: A systematic review

The use of force platform technologies to assess standing balance is common across a range of clinical areas. Numerous researchers have evaluated the low-cost Wii Balance Board (WBB) for its utility in assessing balance, with variable findings. This review aimed to systematically evaluate the reliability and concurrent validity of the WBB for assessment of static standing balance. Articles were retrieved from six databases (Medline, SCOPUS, EMBASE, CINAHL, Web of Science, Inspec) from 2007 to 2017. After independent screening by two reviewers, 25 articles were included. Two reviewers performed the data extraction and quality assessment. Test-retest reliability was investigated in 12 studies, with intraclass correlation coefficients or Pearsons correlation values showing a range from poor to excellent reliability (range: 0.27 to 0.99). Concurrent validity (i.e. comparison with another force platform) was examined in 21 studies, and was generally found to be excellent in studies examining the association between the same outcome measures collected on both devices. For studies reporting predominantly poor to moderate validity, potentially influential factors included the choice of 1) criterion reference (e.g. not a common force platform), 2) test duration (e.g. <30 s for double leg), 3) outcome measure (e.g. comparing a centre of pressure variable from the WBB with a summary score from the force platform), 4) data acquisition platform (studies using Apple iOS reported predominantly moderate validity), and 5) low sample size. In conclusion, evidence suggests that the WBB can be used as a reliable and valid tool for assessing standing balance. Protocol registration number: PROSPERO 2017: CRD42017058122.