Accuracy of Sensor-Based Measurement of Clinically Relevant Motor Activities in Daily Life of Children With Mobility Impairments.

OBJECTIVE: This study aimed to determine the accuracy of 3 sensor configurations and corresponding algorithms deriving clinically relevant outcomes of everyday life motor activities in children undergoing rehabilitation. These outcomes were identified in 2 preceding studies assessing the needs of pediatric rehabilitation. The first algorithm estimates the duration of lying, sitting, and standing positions and the number of sit-to-stand transitions with data from a trunk and a thigh sensor. The second algorithm detects active and passive wheeling periods with data from a wrist and a wheelchair sensor. The third algorithm detects free and assisted walking periods and estimates the covered altitude change during stair climbing with data from a single ankle sensor and a sensor placed on walking aids. DESIGN: The participants performed a semi-structured activity circuit while wearing inertial sensors on both wrists, the sternum, and the thigh and shank of the less-affected side. The circuit included watching a movie, playing, cycling, drinking, and moving around between facilities. Video recordings, which 2 independent researchers labeled, served as reference criteria to determine the algorithms' performance. SETTING: In-patient rehabilitation center. PARTICIPANTS: Thirty-one children and adolescents with mobility impairments who were able to walk or use a manual wheelchair for household distances (N=31). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE(S): The algorithms' activity classification accuracies. RESULTS: The activity classification accuracy was 97% for the posture detection algorithm, 96% for the wheeling detection algorithm, and 93% for the walking detection algorithm. CONCLUSION(S): The 3 sensor configurations and corresponding algorithms presented in this study revealed accurate measurements of everyday life motor activities in children with mobility impairments. To follow-up on this promising results, the sensor systems needs to be tested in long-term measurements outside the clinic before using the system to determine the children's motor performance in their habitual environment for clinical and scientific purposes.

Acceptability of wearable inertial sensors, completeness of data, and day-to-day variability of everyday life motor activities in children and adolescents with neuromotor impairments.

Monitoring the patients' motor activities in a real-world setting would provide essential information on their functioning in daily life. In this study, we used wearable inertial sensors to monitor motor activities of children and adolescents with congenital and acquired brain injuries. We derived a set of clinically meaningful performance measures and addressed the following research questions: Is the target population willing to wear the sensors in their habitual environment? Which factors lead to missing data, and can we avoid them? How many measurement days are needed to obtain reliable estimates of the children's and adolescents' motor performance? The study participants wore our sensor system for seven consecutive days during waking hours. First, we derived the daily hand use of all participants, the duration of different body positions and the wheeling activity of individuals using a manual wheelchair, and walking-related measures in individuals being able to walk. Then, we analyzed the reasons for missing data and determined the reliability of the performance measures mentioned above. The large majority (41 of 43 participants) was willing to wear the sensor system for a week. However, forgetting to reattach the sensors after charging them overnight and taking them off during bathing and swimming was the main contributor to missing data. Consequently, improved battery life and waterproofness of the sensor technology are essential requirements for measurements in daily life. Besides, 5 of 11 performance measures showed significant differences between weekdays and weekend days. The reliability, measured with the intraclass correlation coefficient, ranged between 0.82 and 0.98. Seven measurement days were enough to obtain significantly higher reliability scores than the desired level of 0.8 for all but two performance measures. In children and adolescents with neuromotor impairments, we recommend monitoring everyday life motor activities on seven consecutive days. The target population accepted this measurement protocol, it covers school days and weekend days, and the number of measurement days is sufficient to obtain reliable estimates of motor performance.

Accuracy and comparison of sensor-based gait speed estimations under standardized and daily life conditions in children undergoing rehabilitation.

BACKGROUND: Gait speed is a widely used outcome measure to assess the walking abilities of children undergoing rehabilitation. It is routinely determined during a walking test under standardized conditions, but it remains unclear whether these outcomes reflect the children's performance in daily life. An ankle-worn inertial sensor provides a usable opportunity to measure gait speed in the children's habitual environment. However, sensor-based gait speed estimations need to be accurate to allow for comparison of the children's gait speed between a test situation and daily life. Hence, the first aim of this study was to determine the measurement error of a novel algorithm that estimates gait speed based on data of a single ankle-worn inertial sensor in children undergoing rehabilitation. The second aim of this study was to compare the children's gait speed between standardized and daily life conditions. METHODS: Twenty-four children with walking impairments completed four walking tests at different speeds (standardized condition) and were monitored for one hour during leisure or school time (daily life condition). We determined accuracy by comparing sensor-based gait speed estimations with a reference method in both conditions. Eventually, we compared individual gait speeds between the two conditions. RESULTS: The measurement error was 0.01 ± 0.07 m/s under the standardized and 0.04 ± 0.06 m/s under the daily life condition. Besides, the majority of children did not use the same speed during the test situation as in daily life. CONCLUSION: This study demonstrates an accurate method to measure children's gait speed during standardized walking tests and in the children's habitual environment after rehabilitation. It only requires a single ankle sensor, which potentially increases wearing time and data quality of measurements in daily life. We recommend placing the sensor on the less affected side, unless the child wears one orthosis. In this latter case, the sensor should be placed on the side with the orthosis. Moreover, this study showed that most children did not use the same speed in the two conditions, which encourages the use of wearable inertial sensors to assess the children's walking performance in their habitual environment following rehabilitation.

Sensor-based outcomes to monitor everyday life motor activities of children and adolescents with neuromotor impairments: A survey with health professionals.

In combination with appropriate data processing algorithms, wearable inertial sensors enable the measurement of motor activities in children's and adolescents' habitual environments after rehabilitation. However, existing algorithms were predominantly designed for adult patients, and their outcomes might not be relevant for a pediatric population. In this study, we identified the needs of pediatric rehabilitation to create the basis for developing new algorithms that derive clinically relevant outcomes for children and adolescents with neuromotor impairments. We conducted an international survey with health professionals of pediatric neurorehabilitation centers, provided them a list of 34 outcome measures currently used in the literature, and asked them to rate the clinical relevance of these measures for a pediatric population. The survey was completed by 62 therapists, 16 doctors, and 9 nurses of 16 different pediatric neurorehabilitation centers from Switzerland, Germany, and Austria. They had an average work experience of 13 ± 10 years. The most relevant outcome measures were the duration of lying, sitting, and standing positions; the amount of active self-propulsion during wheeling periods; the hand use laterality; and the duration, distance, and speed of walking periods. The health profession, work experience, and workplace had a minimal impact on the priorities of health professionals. Eventually, we complemented the survey findings with the family priorities of a previous study to provide developers with the clinically most relevant outcomes to monitor everyday life motor activities of children and adolescents with neuromotor impairments.

Concurrent Validity of Different Sensor-Based Measures: Activity Counts Do Not Reflect Functional Hand Use in Children and Adolescents With Upper Limb Impairments.

OBJECTIVE: To investigate the concurrent validity of 4 different outcome measures to determine daily functional hand use with wrist-worn inertial sensors in children with upper limb impairments. We hypothesized that the commonly used activity counts are biased by walking and wheeling activities, while measures that exclude arm movements during these periods with activity detection algorithms or by limiting the analysis to a range of functional forearm elevation would lead to more valid estimates of daily hand use. DESIGN: Concurrent validity study with video-based observations of functional hand use serving as the criterion measure. SETTING: The participants were videotaped while performing an activity circuit at the rehabilitation center and wearing inertial sensors. PARTICIPANTS: A convenience sample of 30 school-aged children and adolescents with upper limb impairments. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Spearman rank correlation coefficients ρ between the criterion measure and 4 sensor-based measures: activity counts, combining activity counts with activity detection algorithms (arm activity counts), limiting activity counts to a functional range of forearm elevation (functional activity counts), and a threshold-based approach limited to the same range of forearm elevation (gross arm movements). RESULTS: Activity counts (ρ=0.43) and gross arm movements (ρ=0.57) did not reveal valid estimates of daily hand use. In contrast, arm and functional activity counts correlated significantly stronger with the criterion measure and revealed valid correlation coefficients of 0.78 and 0.71, respectively. CONCLUSIONS: Activity counts should not be used to measure daily hand use because they are biased by walking and wheeling activities. Arm and functional activity counts provide better and valid alternatives. The selection of these 2 approaches depends on the availability and accuracy of activity detection algorithms and on the users' willingness to wear additional sensors in daily life.

Systematic review on the application of wearable inertial sensors to quantify everyday life motor activity in people with mobility impairments.

BACKGROUND: Recent advances in wearable sensor technologies enable objective and long-term monitoring of motor activities in a patient's habitual environment. People with mobility impairments require appropriate data processing algorithms that deal with their altered movement patterns and determine clinically meaningful outcome measures. Over the years, a large variety of algorithms have been published and this review provides an overview of their outcome measures, the concepts of the algorithms, the type and placement of required sensors as well as the investigated patient populations and measurement properties. METHODS: A systematic search was conducted in MEDLINE, EMBASE, and SCOPUS in October 2019. The search strategy was designed to identify studies that (1) involved people with mobility impairments, (2) used wearable inertial sensors, (3) provided a description of the underlying algorithm, and (4) quantified an aspect of everyday life motor activity. The two review authors independently screened the search hits for eligibility and conducted the data extraction for the narrative review. RESULTS: Ninety-five studies were included in this review. They covered a large variety of outcome measures and algorithms which can be grouped into four categories: (1) maintaining and changing a body position, (2) walking and moving, (3) moving around using a wheelchair, and (4) activities that involve the upper extremity. The validity or reproducibility of these outcomes measures was investigated in fourteen different patient populations. Most of the studies evaluated the algorithm's accuracy to detect certain activities in unlabeled raw data. The type and placement of required sensor technologies depends on the activity and outcome measure and are thoroughly described in this review. The usability of the applied sensor setups was rarely reported. CONCLUSION: This systematic review provides a comprehensive overview of applications of wearable inertial sensors to quantify everyday life motor activity in people with mobility impairments. It summarizes the state-of-the-art, it provides quick access to the relevant literature, and it enables the identification of gaps for the evaluation of existing and the development of new algorithms.

Validity and variability of center of pressure measures to quantify trunk control in stroke patients during quiet sitting and reaching tasks.

BACKGROUND: In the immediate period following stroke, sitting balance is one of the most important predictors of functional recovery at discharge after rehabilitation. Thus, sitting balance determines the content of the early phase of stroke rehabilitation and an appropriate measurement tool is important. RESEARCH QUESTION: The aim of this study is to investigate the concurrent validity of center of pressure (CoP) excursions of patients seated on a force plate, as well as to examine the daily variability of trunk control after stroke. METHODS: Twenty stroke patients at an inpatient rehabilitation clinic underwent two assessment sessions, on average eight hours apart. Each session comprised two trials: quiet sitting for 30 s; extended reaching in forward, backward, left and right directions. The Trunk Impairment Scale (TIS) was measured during the first session. CoP excursions were measured to determine the outcomes of sway area and sway velocity during stable sitting and the maximal excursions in frontal and sagittal planes during the reaching tasks. RESULTS: High Spearman's correlations (0.72, 0.79) were found between the TIS and the frontal and sagittal excursions. However, only low correlations between the TIS and the sway area and sway velocity were observed. Within sessions, all CoP outcomes showed high ICCs (0.73-1.00). Between sessions, high ICCs (0.86-0.93) were found except for sway velocity (ICC 0.51). Sway velocity increased significantly between sessions. SIGNIFICANCE: Frontal and sagittal CoP excursions during reaching tasks appear to be valid measurement parameters to evaluate trunk control in patients after stroke. Only small variability was observed and no significant differences between consecutive days.

Protocol of a systematic review on the application of wearable inertial sensors to quantify everyday life motor activity in people with mobility impairments.

BACKGROUND: People with mobility impairments may have difficulties in everyday life motor activities, and assessing these difficulties is crucial to plan rehabilitation interventions and evaluate their effectiveness. Wearable inertial sensors enable long-term monitoring of motor activities in a patient's habitual environment and complement clinical assessments which are conducted in a standardised environment. The application of wearable sensors requires appropriate data processing algorithms to estimate clinically meaningful outcome measures, and this review will provide an overview of previously published measures, their underlying algorithms, sensor placement, and measurement properties such as validity, reproducibility, and feasibility. METHODS: We will screen the literature for studies which applied inertial sensors to people with mobility impairments in free-living conditions, described the data processing algorithm reproducibly, and calculated everyday life motor activity-related outcome measures. Three databases (MEDLINE, EMBASE, and SCOPUS) will be searched with terms out of four different categories: study population, measurement tool, algorithm, and outcome measure. Abstracts and full texts will be screened independently by the two review authors, and disagreement will be solved by discussion and consensus. Data will be extracted by one of the review authors and verified by the other. It includes the type of outcome measures, the underlying data processing algorithm, the required sensor technology, the corresponding sensor placement, the measurement properties, and the target population. We expect to find a high heterogeneity of outcome measures and will therefore provide a narrative synthesis of the extracted data. DISCUSSION: This review will facilitate the selection of an appropriate sensor setup for future applications, contain recommendations about the design of data processing algorithms as well as their evaluation procedure, and present a gap for innovative, new algorithms, and devices. SYSTEMATIC REVIEW REGISTRATION: International prospective register of systematic reviews (PROSPERO): CRD42017069865 .

Reproducibility of a new signal processing technique to assess joint sway during standing.

Postural control strategies can be investigated by kinematic analysis of joint movements. However, current research is focussing mainly on the analysis of centre of pressure excursion and lacks consensus on how to assess joint movement during postural control tasks. This study introduces a new signal processing technique to comprehensively quantify joint sway during standing and evaluates its reproducibility. Fifteen patients with non-specific low back pain and ten asymptomatic participants performed three repetitions of a 60-second standing task on foam surface. This procedure was repeated on a second day. Lumbar spine movement was recorded using an inertial measurement system. The signal was temporally divided into six sections. Two outcome variables (mean absolute sway and sways per second) were calculated for each section. The reproducibility of single and averaged measurements was quantified with linear mixed-effects models and the generalizability theory. A single measurement of ten seconds duration revealed reliability coefficients of .75 for mean absolute sway and .76 for sways per second. Averaging a measurement of 40 seconds duration on two different days revealed reliability coefficients higher than .90 for both outcome variables. The outcome variables' reliability compares favourably to previously published results using different signal processing techniques or centre of pressure excursion. The introduced signal processing technique with two outcome variables to quantify joint sway during standing proved to be a highly reliable method. Since different populations, tasks or measurement tools could influence reproducibility, further investigation in other settings is still necessary. Nevertheless, the presented method has been shown to be highly promising.

Reliability of lumbar movement dysfunction tests for chronic low back pain patients.

Assessment of lumbar movement dysfunction commonly comprises trunk range of motion (ROM), movement or control impairment (MCI), and reposition error (RE). Those assessments are typically based on visual observation. Consequently it is not possible to reliably quantify back movements for intersubject comparisons, or for monitoring changes before and after an intervention. Inertial measurement unit (IMU)-systems could be used to quantify these movement dysfunctions in clinical settings. The aim of this study was to evaluate the reliability of movement dysfunction tests when measured with a novel IMU-system. The reliability of eleven movement dysfunction tests (four ROM, six MCI and one RE tests) were analysed using generalizability-theory and minimal detectable change, measuring 21 chronic low back pain patients in seven trials on two days. Reliability varied across tests and variables. Four ROM and selected MCI tests and variables were identified as reliable. On average, ROM test were more reliable, compared to MCI and RE tests. An attempt should be made to improve the reliability of MCI and RE measures, for example through better standardizations. Subsequently these measures should be studied further for intersubject comparisons and monitoring changes after an intervention.

Between-day reliability of three-dimensional motion analysis of the trunk: A comparison of marker based protocols.

Motion capture of the trunk using three-dimensional optoelectronic systems and skin markers placed on anatomical landmarks is prone to error due to marker placement, thus decreasing between-day reliability. The influence of these errors on angular output might be reduced by using an overdetermined number of markers and optimization algorithms, or by defining the neutral position using a reference trial. The purpose of this study was to quantify and compare the between-day reliability of trunk kinematics, when using these methods. In each of two sessions, 20 subjects performed four movement tasks. Trunk kinematics were established through the plug-in-gait protocol, the point cloud optimization algorithm, and by defining upright standing as neutral position. Between-day reliability was analyzed using generalizability theory and quantified by indexes of dependability. Across all movement tasks, none of the methods was superior in terms of between-day reliability. The point cloud algorithm did not improve between-day reliability, but did result in 24.3% greater axial rotation angles. The definition of neutral position by means of a reference trial revealed 5.8% higher indexes of dependability for lateral bending and axial rotation angles, but 13.7% smaller indexes of dependability for flexion angles. Further, using a reference trial resulted in 8.3° greater trunk flexion angles. Therefore, the selection of appropriate marker placement and the corresponding calculation of angular output are dependent on the movement task and the underlying research question.

Adherence to home exercises in non-specific low back pain. A randomised controlled pilot trial.

Specific exercises for the improvement of movement control of the lumbopelvic region are well-established for patients with non-specific low back pain (NSLBP) and movement control impairment (MCI). However, a lack of adherence to home exercise regimens is often observed. The aim of the study was to explore the differences in home exercise (HE) adherence between patients who perform conventional exercises and those who exercise with Augmented Feedback (AF). Twenty patients with NSLBP and MCI were randomly allocated into two groups. The physiotherapy group (PT group) completed conventional exercises, and the AF group exercised with an AF system that was designed for use in therapy settings. The main outcome measure was self-reported adherence to the home exercise regimen. There was no significant difference in HE duration between the groups (W = 64, p = 0.315). The AF group exercised for a median of 9 min and 4 s (IQR = 3'59"), and the PT group exercised for 4 min and 19 s (IQR = 8'30"). Exercising with AF led to HE times that were similar to those of conventional exercise, and AF might be used as an alternative therapy method for home exercise.

Low back pain and postural control, effects of task difficulty on centre of pressure and spinal kinematics.

Association of low back pain and standing postural control (PC) deficits are reported inconsistently. Demands on PC adaptation strategies are increased by restraining the input of visual or somatosensory senses. The objectives of the current study are, to investigate whether PC adaptations of the spine, hip and the centre of pressure (COP) differ between patients reporting non-specific low back pain (NSLBP) and asymptomatic controls. The PC adaption strategies of the thoracic and lumbar spine, the hip and the COP were measured in fifty-seven NSLBP patients and 22 asymptomatic controls. We tested three "feet together" conditions with increasing demands on PC strategies, using inertial measurement units (IMUs) on the spine and a Wii balance board for centre of pressure (COP) parameters. The differences between NSLBP patients and controls were most apparent when the participants were blindfolded, but remaining on a firm surface. While NSLBP patients had larger thoracic and lumbar spine mean absolute deviations of position (MADpos) in the frontal plane, the same parameters decreased in control subjects (relative change (RC): 0.23, 95% confidence interval: 0.03 to 0.45 and 0.03 to 0.48). The Mean absolute deviation of velocity (MADvel) of the thoracic spine in the frontal plane showed a similar and significant effect (RC: 0.12 95% CI: 0.01 to 0.25). Gender, age and pain during the measurements affected some parameters significantly. PC adaptions differ between NSLBP patients and asymptomatic controls. The differences are most apparent for the thoracic and lumbar parameters of MADpos, in the frontal plane and while the visual condition was removed.