Concurrent Validity of a Custom Method for Markerless 3D Full-Body Motion Tracking of Children and Young Adults Based on a Single RGB-D Camera.

Low-cost, portable RGB-D cameras with integrated body tracking functionality enable easy-to-use 3D motion analysis without requiring expensive facilities and specialized personnel. However, the accuracy of existing systems is insufficient for most clinical applications. In this study, we investigated the concurrent validity of our custom tracking method based on RGB-D images with respect to a gold-standard marker-based system. Additionally, we analyzed the validity of the publicly available Microsoft Azure Kinect Body Tracking (K4ABT). We recorded 23 typically developing children and healthy young adults (aged 5 to 29 years) performing five different movement tasks using a Microsoft Azure Kinect RGB-D camera and a marker-based multi-camera Vicon system simultaneously. Our method achieved a mean per joint position error over all joints of 11.7 mm compared to the Vicon system, and 98.4% of the estimated joint positions had an error of less than 50 mm. Pearson's correlation coefficients r ranged from strong ( r =0.64) to almost perfect ( 0.99). K4ABT demonstrated satisfactory accuracy most of the time but showed short periods of tracking failures in nearly two-thirds of all sequences limiting its use for clinical motion analysis. In conclusion, our tracking method highly agrees with the gold standard system. It paves the way towards a low-cost, easy-to-use, portable 3D motion analysis system for children and young adults.

Contextual interference in children with brain lesions: a pilot study investigating blocked vs. random practice order of an upper limb robotic exergame.

INTRODUCTION: Evidence about contextual interference in children with brain lesions when practising motor tasks is lacking. Our main objective was to evaluate the feasibility of a randomised controlled trial (RCT) comparing blocked with random practice order of an upper limb robotic exergame to improve reaching in children with neuromotor disorders with a pilot trial. METHODS: We recruited children with brain lesions and impaired upper limb functions who underwent a 3-week schedule that consisted of baseline assessments, intervention period (participants were randomised to a blocked or random order group), and follow-up assessment. We evaluated ten feasibility criteria, including the practicability of the inclusion/exclusion criteria, recruitment rate, feasibility of randomisation, scheduling procedure, and the participants' programme adherence. RESULTS: The inclusion/exclusion criteria were not completely feasible as patients who were not able to perform the exergames were included. Twelve participants were recruited, and six datasets were used for analysis. The scheduling and randomisation procedures were generally feasible, but the procedure was only partially feasible for the participants, as some sessions were aborted due to lack of motivation and fatigue. CONCLUSION: An RCT following this study protocol is not feasible. We formulated suggestions for future studies that aim to investigate contextual interference as in this pilot study. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02443857 , registered on May 14, 2015.

Prefrontal Cortex and Supplementary Motor Area Activation During Robot-Assisted Weight-Supported Over-Ground Walking in Young Neurological Patients: A Pilot fNIRS Study.

Introduction: Rehabilitation therapy devices are designed for practicing intensively task-specific exercises inducing long-term neuroplastic changes underlying improved functional outcome. The Andago enables over-ground walking with bodyweight support requiring relatively high cognitive demands. In this study, we investigated whether we could identify children and adolescents with neurological gait impairments who show increased hemodynamic responses of the supplementary motor area (SMA) or prefrontal cortex (PFC) measured with functional near-infrared spectroscopy (fNIRS) when walking in Andago compared to walking on a treadmill. We further assessed the practicability and acceptability of fNIRS. Methods: Thirteen participants (two girls, 11 boys, age 8.0-15.7 years) with neurological impairments walked in the Andago and on a treadmill under comparable conditions. We measured hemodynamic responses over SMA and PFC during 10 walks (each lasting 20 s.) per condition and analyzed the data according to the latest recommendations. In addition, we listed technical issues, stopped the time needed to don fNIRS, and used a questionnaire to assess acceptability. Results: Hemodynamic responses varied largely between participants. Participants with a typical hemodynamic response (i.e., increased oxygenated hemoglobin concentration) showed large cortical activations during walking in Andago compared to treadmill walking (large effect sizes, i.e., for SMA: r = 0.91, n = 4; for PFC: r = 0.62, n = 3). Other participants showed atypical (SMA: n = 2; PFC: n = 4) or inconclusive hemodynamic responses (SMA: n = 5; PFC: n = 4). The median time for donning fNIRS was 28 min. The questionnaire indicated high acceptance of fNIRS, despite that single participants reported painful sensations. Discussion: Repetitive increased activation of cortical areas like the SMA and PFC might result in long-term neuroplastic changes underlying improved functional outcome. This cross-sectional pilot study provides first numbers on hemodynamic responses in SMA and PFC during walking in Andago in children with neurological impairments, reveals that only a small proportion of the participants shows typical hemodynamic responses, and reports that fNIRS requires considerable time for donning. This information is needed when designing future longitudinal studies to investigate whether increased brain activation of SMA and PFC during walking in Andago could serve as a biomarker to identify potential therapy responders among children and adolescents undergoing neurorehabilitation.

Correction to: The FreeD module for the Lokomat facilitates a physiological movement pattern in healthy people - a proof of concept study.

The original article [1] contains an error whereby the legends of Figs. 3 and 4 are erroneously swapped. As such, the correct configuration of these legends can be seen in the same figures below instead.

The FreeD module for the Lokomat facilitates a physiological movement pattern in healthy people - a proof of concept study.

BACKGROUND: A contralateral pelvic drop, a transverse rotation and a lateral translation of the pelvis are essential features of normal human gait. These motions are often restricted in robot-assisted gait devices. The optional FreeD module of the driven gait orthosis Lokomat (Hocoma AG, Switzerland) incorporates guided lateral translation and transverse rotation of the pelvis. It consequently should support weight shifting during walking. This study aimed to investigate the influence of the FreeD module on trunk kinematics and hip and trunk muscle activity. METHODS: Thirty- one healthy adults participated. A video analysis of their trunk movements was performed to investigate the lateral chest and pelvis displacement within the Lokomat (with and without FreeD), and this was compared to treadmill walking. Furthermore, surface electromyography (sEMG) signals from eight muscles were collected during walking in the Lokomat (with and without FreeD), on the treadmill, and overground. To compare the similarity of the sEMG patterns, Spearman's correlation analyses were applied. RESULTS: Walking with FreeD elicited a significantly higher lateral pelvis displacement and a lower lateral chest displacement (relative to the pelvis) compared to walking with a fixated pelvis. No significant differences in the sEMG patterns were found for the Lokomat conditions (with and without FreeD) when comparing it to treadmill or overground walking. CONCLUSIONS: The differences in pelvis displacement act as a proof of concept of the FreeD module. The reduction of relative lateral chest movement corresponds to a decrease in compensatory trunk movements and has its origin in allowing weight shifting through the FreeD module. Both Lokomat conditions showed very similar muscle activity patterns of the trunk and hip compared to overground and treadmill walking. This indicates that the Lokomat allows a physiological muscle activity of the trunk and hip during gait.