Database of lower limb kinematics and electromyography during gait-related activities in able-bodied subjects.

This data descriptor describes the Roessingh Research & Development-MyLeg database for activity prediction (MyPredict), containing three data sets. These data sets contain data from 55 able-bodied subjects, mean age 24 ± 2 years, measured in 85 measurement sessions. Measurement sessions consisted of trials containing sitting, standing, overground walking, stair ascent, stair descent, ramp ascent, ramp descent, walking on uneven terrain and walking in simulated confined spaces. Subjects were measured using eight inertial measurement units in combination with different types of sEMG. Recorded kinematics consisted of joint angles, sensor accelerations, angular velocity, orientation and virtual marker positions. sEMG was recorded using bipolar sEMG, multi-array sEMG or a combination of both. All data showed excellent correlation with other online available data sets. The data reported in this descriptor forms a solid basis for research into myoelectric pattern recognition, myoelectric control development and electromyography to be used in data-driven applications.

Relevance of hazards in exoskeleton applications: a survey-based enquiry.

Exoskeletons are becoming the reference technology for assistance and augmentation of human motor functions in a wide range of application domains. Unfortunately, the exponential growth of this sector has not been accompanied by a rigorous risk assessment (RA) process, which is necessary to identify the major aspects concerning the safety and impact of this new technology on humans. This situation may seriously hamper the market uptake of new products. This paper presents the results of a survey that was circulated to understand how hazards are considered by exoskeleton users, from research and industry perspectives. Our analysis aimed to identify the perceived occurrence and the impact of a sample of generic hazards, as well as to collect suggestions and general opinions from the respondents that can serve as a reference for more targeted RA. Our results identified a list of relevant hazards for exoskeletons. Among them, misalignments and unintended device motion were perceived as key aspects for exoskeletons' safety. This survey aims to represent a first attempt in recording overall feedback from the community and contribute to future RAs and the identification of better mitigation strategies in the field.

Synchronization of wearable motion capture and EMG measurement systems.

Synchronization of motion capture systems with other modalities in out-of-the-lab settings is not trivial. Various synchronization methods exist, such as using servers or transistor-transistor-logic pulses. However, not all measurement set-ups allow for such synchronization methods. Therefore, we have developed and validated an acceleration based post-measurement method to synchronize an IMU based motion capture system and an EMG measurement device. On top of the thigh IMU an additional accelerometer was placed which was connected to the analog input of the EMG device. By applying cross-correlation continuously, the similarities in the measured acceleration by the two measurement systems can be used for synchronization. We performed a validation measurement on seven able-bodied subjects and tested various correlation window sizes in hour long measurements in an out of the lab setting. It can be concluded that the developed method works for different activities when a suitable window length is chosen for cross-correlation. If no other options are available for synchronization, this correlation based method using an additional accelerometer is a viable option.

Assessing effects of exoskeleton misalignment on knee joint load during swing using an instrumented leg simulator.

BACKGROUND: Exoskeletons are working in parallel to the human body and can support human movement by exerting forces through cuffs or straps. They are prone to misalignments caused by simplified joint mechanics and incorrect fit or positioning. Those misalignments are a common safety concern as they can cause undesired interaction forces. However, the exact mechanisms and effects of misalignments on the joint load are not yet known. The aim of this study was therefore to investigate the influence of different directions and magnitudes of exoskeleton misalignment on the internal knee joint forces and torques of an artificial leg. METHODS: An instrumented leg simulator was used to quantify the changes in knee joint load during the swing phase caused by misalignments of a passive knee brace being manually flexed. This was achieved by an experimenter pulling on a rope attached to the distal end of the knee brace to create a flexion torque. The extension was not actuated but achieved through the weight of the instrumented leg simulator. The investigated types of misalignments are a rotation of the brace around the vertical axis and a translation in anteroposterior as well as proximal/distal direction. RESULTS: The amount of misalignment had a significant effect on several directions of knee joint load in the instrumented leg simulator. In general, load on the knee joint increased with increasing misalignment. Specifically, stronger rotational misalignment led to higher forces in mediolateral direction in the knee joint as well as higher ab-/adduction, flexion and internal/external rotation torques. Stronger anteroposterior translational misalignment led to higher mediolateral knee forces as well as higher abduction and flexion/extension torques. Stronger proximal/distal translational misalignment led to higher posterior and tension/compression forces. CONCLUSIONS: Misalignments of a lower leg exoskeleton can increase internal knee forces and torques during swing to a multiple of those experienced in a well-aligned situation. Despite only taking swing into account, this is supporting the need for carefully considering hazards associated with not only translational but also rotational misalignments during wearable robot development and use. Also, this warrants investigation of misalignment effects in stance, as a target of many exoskeleton applications.

Outdoor E-trike cycling: A low intensity physical activity.

For people with disabilities or chronic diseases, an electrically supported tricycle (e-trike) could facilitate independence and participation in physical activity, and improve health conditions. This study investigates the exercise intensity and perceived exertion of e-trike cycling. Twenty healthy participants cycled on an e-trike with different speeds (12 and 18 km/h) and different levels of electric pedal support at an outdoor athletics track. Exercise intensity was measured with oxygen consumption (V˙O2) using a Cosmed K4B2 analysis unit, perceived exertion was measured with the Borg Rating of Perceived Exertion scale, pedaling power, and engine power were measured with a torque sensor. The effect of speed and support was analyzed with a Linear Mixed Effects model. V˙O2 was 18.67 ± 3.13 ml/kg/min without support, with electric support the exercise intensity was significantly below moderate intensity (i.e. 10.5 ml/kg/min) at t = 11.37, p < .001, 95% CI: 1.90, 2.77. The Borg score without support was 9.79 ± 1.72 and all other conditions below this, which were significantly below moderate intensity (i.e. 11) at t = -3.07, p = .007, 95% CI: -2.04, -0.38. Speed and support significantly affected V˙O2 (F = 185.49, p < .001). E-trike cycling is a low intensity activity, but intensity can be influenced by changing speed and support level.

Safety Assessment of Rehabilitation Robots: A Review Identifying Safety Skills and Current Knowledge Gaps.

The assessment of rehabilitation robot safety is a vital aspect of the development process, which is often experienced as difficult. There are gaps in best practices and knowledge to ensure safe usage of rehabilitation robots. Currently, safety is commonly assessed by monitoring adverse events occurrence. The aim of this article is to explore how safety of rehabilitation robots can be assessed early in the development phase, before they are used with patients. We are suggesting a uniform approach for safety validation of robots closely interacting with humans, based on safety skills and validation protocols. Safety skills are an abstract representation of the ability of a robot to reduce a specific risk or deal with a specific hazard. They can be implemented in various ways, depending on the application requirements, which enables the use of a single safety skill across a wide range of applications and domains. Safety validation protocols have been developed that correspond to these skills and consider domain-specific conditions. This gives robot users and developers concise testing procedures to prove the mechanical safety of their robotic system, even when the applications are in domains with a lack of standards and best practices such as the healthcare domain. Based on knowledge about adverse events occurring in rehabilitation robot use, we identified multi-directional excessive forces on the soft tissue level and musculoskeletal level as most relevant hazards for rehabilitation robots and related them to four safety skills, providing a concrete starting point for safety assessment of rehabilitation robots. We further identified a number of gaps which need to be addressed in the future to pave the way for more comprehensive guidelines for rehabilitation robot safety assessments. Predominantly, besides new developments of safety by design features, there is a strong need for reliable measurement methods as well as acceptable limit values for human-robot interaction forces both on skin and joint level.

Occurrence and Type of Adverse Events During the Use of Stationary Gait Robots-A Systematic Literature Review.

Robot-assisted gait training (RAGT) devices are used in rehabilitation to improve patients' walking function. While there are some reports on the adverse events (AEs) and associated risks in overground exoskeletons, the risks of stationary gait trainers cannot be accurately assessed. We therefore aimed to collect information on AEs occurring during the use of stationary gait robots and identify associated risks, as well as gaps and needs, for safe use of these devices. We searched both bibliographic and full-text literature databases for peer-reviewed articles describing the outcomes of stationary RAGT and specifically mentioning AEs. We then compiled information on the occurrence and types of AEs and on the quality of AE reporting. Based on this, we analyzed the risks of RAGT in stationary gait robots. We included 50 studies involving 985 subjects and found reports of AEs in 18 of those studies. Many of the AE reports were incomplete or did not include sufficient detail on different aspects, such as severity or patient characteristics, which hinders the precise counts of AE-related information. Over 169 device-related AEs experienced by between 79 and 124 patients were reported. Soft tissue-related AEs occurred most frequently and were mostly reported in end-effector-type devices. Musculoskeletal AEs had the second highest prevalence and occurred mainly in exoskeleton-type devices. We further identified physiological AEs including blood pressure changes that occurred in both exoskeleton-type and end-effector-type devices. Training in stationary gait robots can cause injuries or discomfort to the skin, underlying tissue, and musculoskeletal system, as well as unwanted blood pressure changes. The underlying risks for the most prevalent injury types include excessive pressure and shear at the interface between robot and human (cuffs/harness), as well as increased moments and forces applied to the musculoskeletal system likely caused by misalignments (between joint axes of robot and human). There is a need for more structured and complete recording and dissemination of AEs related to robotic gait training to increase knowledge on risks. With this information, appropriate mitigation strategies can and should be developed and implemented in RAGT devices to increase their safety.

Prototype Measuring Device for Assessing Interaction Forces between Human Limbs and Rehabilitation Robots - A Proof of Concept Study.

Rehabilitation robots can provide high intensity and dosage training or assist patients in activities of daily living and decrease physical strain on clinicians. However, the physical human robot interaction poses a major safety issue, as the close physical contact between user and robot can lead to injuries. Moreover, the magnitude of forces as well as best practices for measuring them, are widely unknown. Therefore, a measurement setup was developed to assess normal and tangential forces that occur in the contact area between an arm and a splint. Force sensitive resistors and a force / torque sensor were combined with two different splint shapes. Initial experiments indicated that the setup gives some insight into magnitudes and distribution of normal forces on the splint-forearm-interface. Experiment results show a dependency of force distributions on the splint shape and sensor locations. Based on these outcomes, we proposed an improved setup for subsequent investigations.

Effect of long-term use of ankle-foot orthoses on tibialis anterior muscle electromyography in patients with sub-acute stroke: A randomized controlled trial.

OBJECTIVE: To determine: (i) whether the use of ankle-foot orthoses over a period of 26 weeks affects tibialis anterior muscle activity; (ii) whether the timing of provision of ankle-foot orthoses (early or delayed) affects the results; (iii) whether the provision of ankle-foot orthoses affects tibialis anterior muscle activity within a single measurement. DESIGN: Randomized controlled trial. SUBJECTS: Unilateral hemiparetic subjects, a maximum of 6 weeks post-stroke. METHODS: Subjects were assigned randomly to early (at inclusion; week 1) or delayed provision of ankle-foot orthoses (8 weeks later; week 9). Tibialis anterior electromyography was measured with and without ankle-foot orthoses, in study weeks 1, 9, 17 and 26. RESULTS: A total of 26 subjects were analysed. In a single measurement, use of an ankle-foot orthosis significantly reduced the activity levels of the tibialis anterior muscle during the swing phase (p = 0.041) compared with walking without an ankle-foot or-thosis. During the 26-week follow-up, no changes were found in tibialis anterior muscle activity in the swing phase without an ankle-foot orthosis, both within-groups (p = 0.420 early; p = 0.282 delayed), and between-groups (p = 0.987). After 26 weeks, no differences were found in tibialis anterior muscle activity between both groups in the swing phase, with (p = 0.207) or without ankle-foot orthoses (p = 0.310). CONCLUSION: Use of ankle-foot orthoses post-stroke reduced tibialis anterior muscle activity in the swing phase within 1 measurement; however, long-term use of ankle-foot orthoses for 26 weeks did not affect such activity. Early or delayed provision of ankle-foot orthoses did not affect the findings. The results indicate that there is no need to fear negative consequences on tibialis anterior-activity because of long-term AFO-use (early) after stroke.

Exploration of shoulder load during hand-rim wheelchair start-up with and without power-assisted propulsion in experienced wheelchair users.

BACKGROUND: Frequent start movements occurred during the day, yielding high upper-extremity stress. The high incidence and impact of shoulder injury on daily life wheelchair use made it clinically relevant to investigate whether power-assisted propulsion is beneficial during the start. METHODS: Eleven hand-rim wheelchair users performed a start-movement in an instrumented wheelchair on a flat surface. Test order was randomly assigned to propulsion with and without power-assist. For each subject, parameters were averaged over 3 repeated starts. For statistical analysis Wilcoxon Signed Rank test was used. FINDINGS: Intensity of mechanical shoulder loading decreased during power-assisted propulsion for anterior (147.0 (44.8) versus 121.9 (27.4) N; effect size (r)=-.75), posterior (4.8 (14.1) versus 2.7 (11.6) N; r=-.64) and inferior directed forces (82.6 (27.9) versus 68.9 (22.6) N; r=-.78) and abduction (20.2 (14.6) versus 12.9 (7.8) Nm; r=-.88) and extension moments (20.3 (10.7) versus 13.7 (9.1 Nm; r=-.88). Peak resultant force at the rim significantly decreased from 133.5 (38.4) N to 112.2 (25.4) N (r=-.64) and was accompanied by significant decreased shoulder abduction (35.3 (6.7) versus 33.3 (6.8); r=-.67) and significant increased shoulder extension (13.6 (16.3) versus 20.3 (19.1); r=-.78) during power-assisted start-up. INTERPRETATION: Power-assist hand-rim wheelchairs are effective in reducing external shoulder load and partly effective in reducing force generation in extremes of shoulder motion during start-up. The use of power-assist wheels might reduce the risk of developing shoulder overuse injuries. CLINICAL TRIAL REGISTRATION NUMBER: NTR2661.

Optimal sensor placement for measuring physical activity with a 3D accelerometer.

Accelerometer-based activity monitors are popular for monitoring physical activity. In this study, we investigated optimal sensor placement for increasing the quality of studies that utilize accelerometer data to assess physical activity. We performed a two-staged study, focused on sensor location and type of mounting. Ten subjects walked at various walking speeds on a treadmill, performed a deskwork protocol, and walked on level ground, while simultaneously wearing five ProMove2 sensors with a snug fit on an elastic waist belt. We found that sensor location, type of activity, and their interaction-effect affected sensor output. The most lateral positions on the waist belt were the least sensitive for interference. The effect of mounting was explored, by making two subjects repeat the experimental protocol with sensors more loosely fitted to the elastic belt. The loose fit resulted in lower sensor output, except for the deskwork protocol, where output was higher. In order to increase the reliability and to reduce the variability of sensor output, researchers should place activity sensors on the most lateral position of a participant's waist belt. If the sensor hampers free movement, it may be positioned slightly more forward on the belt. Finally, sensors should be fitted tightly to the body.

Comparison of shoulder load during power-assisted and purely hand-rim wheelchair propulsion.

BACKGROUND: Repetitive forces and moments are among the work requirements of hand-rim wheelchair propulsion that are related to shoulder injuries. No previous research has been published about the influence of power-assisted wheelchair propulsion on these work requirements. The purpose of our study was therefore to determine the influence of power-assisted propulsion on shoulder biomechanics and muscle activation patterns. We also explored the theoretical framework for the effectiveness of power-assisted propulsion in preventing shoulder injuries by decreasing the work requirements of hand-rim wheelchair propulsion. METHODS: Nine non-wheelchair users propelled a hand-rim wheelchair on a treadmill at 0.9 m/s. Shoulder biomechanics, and muscle activation patterns, were compared between propulsion with and without power-assist. FINDINGS: Propulsion frequency did not differ significantly between the two conditions (Wilcoxon Signed Rank test/significance level/effect size:4/.314/-.34). During power-assisted propulsion we found significantly decreased maximum shoulder flexion and internal rotation angles (1/.015/-.81 and 0/.008/-.89) and decreased peak force on the rim (0/.008/-.89). This resulted in decreased shoulder flexion, adduction and internal rotation moments (2/.021/-.77; 0/.008/-.89 and 1/.011/-.85) and decreased forces at the shoulder in the posterior, superior and lateral directions (2/.021/-.77; 2/.008/-.89 and 2/.024/-.75). Muscle activation in the pectoralis major, posterior deltoid and triceps brachii was also decreased (2/.038/-.69; 1/.015/-.81 and 1/.021/-.77). INTERPRETATION: Power-assist influenced the work requirements of hand-rim wheelchair propulsion by healthy subjects. It was primarily the kinetics at rim and shoulder which were influenced by power-assisted propulsion. Additional research with actual hand-rim wheelchair users is required before extrapolation to routine clinical practice.

The myofeedback-based teletreatment system and its evaluation.

The myofeedback-based teletreatment system allows patients to receive tactile and/or visual feedback on muscle activity and muscle relaxation times. Health-care professionals can analyse muscle activity and muscle relaxation times and provide guidance to the patient on the course of treatment. The system was evaluated in a small clinical trial. Qualitative data were obtained by interviews and visual inspection of graphical patient data during the trial. Quantitative data were based on post-trial data analysis. We used a revised version of the information systems success model to evaluate the teletreatment system, and focused on the success categories of system use and user satisfaction. The evaluation found good input data quality, system quality and information quality. Both system use and user satisfaction were good. Thus the teletreatment system appears suitable for small scale clinical deployment. However, the sensory components suffered from heavy use and embedded software problems which made them unreliable. Large scale deployment requires improvement in terms of durability and reliability of the system's sensors.

Back muscle activation patterns in chronic low back pain during walking: a "guarding" hypothesis.

OBJECTIVES: To investigate whether patients with chronic low back pain (CLBP) show "guarded" movements during walking. It is hypothesized that guarding will be reflected by increased lumbar muscle activity during all periods of stride and secondary, relatively lesser relaxation during periods of swing compared with double support. Furthermore, it is hypothesized that higher levels of perceived fear and disability are related to increased muscle activity and less relative relaxation. MATERIALS AND METHODS: In a cross-sectional study 63 patients with CLBP and 33 healthy controls walked on a treadmill at 3.8 km/h. Surface electromyography (sEMG) data of the erector spinae were obtained and smoothed rectified sEMG (SRE) values were calculated per period of swing and double support. The ratio of SRE values in swing to double support was used as a measure of relative relaxation (SRE ratio). In addition, the relationship between SRE values, the Roland Morris Disability Questionnaire, and the Tampa Scale for Kinesiophobia was analyzed in patients with CLBP. RESULTS: Mean SRE values were significantly higher in patients with CLBP than in controls both during periods of double support and swing. SRE ratios were not significantly different between groups. Results showed no influence of disability or fear of movement on either SRE values or ratios. DISCUSSION: In patients with CLBP, increased lumbar muscle activity during all periods of stride, with comparable alteration between swing and double support, suggests difficulties with total muscle relaxation. On the basis of this evaluation, it is concluded that patients with CLBP show a guarding mechanism during walking. No relationship is found between perceived fear, disability, and muscle activity.

A staged approach evaluation of remotely supervised myofeedback treatment (RSMT) in women with neck-shoulder pain due to computer work.

Remotely supervised myofeedback treatment (RSMT) is a relatively new intervention aimed at reducing neck-shoulder pain and disabilities. Subjects are equipped with a garment that can be worn under the clothes during daily work. Dry surface electrodes incorporated in this garment measure muscle activation (sEMG) of the trapezius muscle. The garment is connected to an ambulant device that provides feedback to the subject when muscle relaxation is insufficient. sEMG data are also sent to a secured server that is accessible by therapists for remote counseling purposes. In conformance with the evaluation stages of DeChant, RSMT was evaluated on technical feasibility, patient satisfaction, and changes in clinical outcomes. In addition, subjects were asked about their willingness to pay. The study population consisted of 10 female workers suffering from neck-shoulder pain related to computer work. Results show that in 78% of the remote counseling sessions, sufficient amounts of data were available at the server for the therapist to make an assessment of muscle tension needed for the remote counseling sessions. Subjects were highly satisfied about the usefulness and ease of use of the remote counseling. However, they were less satisfied with the technical functioning of the myofeedback system. Eighty percent of the subjects reported a reduction in pain intensity and disability directly after RSMT. Subjects were willing to contribute a maximum of 200 euro for RSMT. Based on this study, it can be concluded that RSMT is technically feasible and induces changes in clinical outcomes. However, further improvements to technical functioning and research into the clinical effectiveness are needed before this treatment can go into real deployment.