Shoulder Pain in Persons With Tetraplegia and the Association With Force Application During Manual Wheelchair Propulsion.

Objective: To investigate the association between propulsion biomechanics, including force application and spatio-temporal characteristics, and shoulder pain in persons with tetraplegia. Design: Cross-sectional, observational study. Setting: Non-university research institution. Participants: 16 community dwelling, wheelchair dependent persons with a chronic tetraplegia between C4 and C7, with and without shoulder pain (age, 49.1±11.7 years; 94% men, 23.4±9.5 years past injury). Interventions: Not applicable. Main Outcome Measures: Force application and spatio-temporal characteristics of wheelchair propulsion on a treadmill (0.56 m/s, 10W and 0.83 m/s, 15W). Participants were stratified in groups with low, moderate, and high pain based on their Wheelchair User Shoulder Pain Index (WUSPI) score on the day of measurement. Results: The mixed-effect multilevel analysis showed that wheelchair users with high levels of shoulder pain applied propulsion force more effectively (and with a lower medial component) and over a longer push angle, thus shortening the recovery time as compared with persons with low or moderate levels of shoulder pain. Conclusions: In contrast with previous results from persons with a paraplegia, persons with tetraplegia and high levels of shoulder pain propel their wheelchair more optimal with regard to risk factors for shoulder pain. Our results therefore affirm that there is a different interaction of shoulder pain and propulsion biomechanics in persons with a tetraplegia which should be considered when further analyzing risk factors for shoulder pain in wheelchair users or applying literature results to different patient populations.

Real-Life Wheelchair Mobility Metrics from IMUs.

Daily wheelchair ambulation is seen as a risk factor for shoulder problems, which are prevalent in manual wheelchair users. To examine the long-term effect of shoulder load from daily wheelchair ambulation on shoulder problems, quantification is required in real-life settings. In this study, we describe and validate a comprehensive and unobtrusive methodology to derive clinically relevant wheelchair mobility metrics (WCMMs) from inertial measurement systems (IMUs) placed on the wheelchair frame and wheel in real-life settings. The set of WCMMs includes distance covered by the wheelchair, linear velocity of the wheelchair, number and duration of pushes, number and magnitude of turns and inclination of the wheelchair when on a slope. Data are collected from ten able-bodied participants, trained in wheelchair-related activities, who followed a 40 min course over the campus. The IMU-derived WCMMs are validated against accepted reference methods such as Smartwheel and video analysis. Intraclass correlation (ICC) is applied to test the reliability of the IMU method. IMU-derived push duration appeared to be less comparable with Smartwheel estimates, as it measures the effect of all energy applied to the wheelchair (including thorax and upper extremity movements), whereas the Smartwheel only measures forces and torques applied by the hand at the rim. All other WCMMs can be reliably estimated from real-life IMU data, with small errors and high ICCs, which opens the way to further examine real-life behavior in wheelchair ambulation with respect to shoulder loading. Moreover, WCMMs can be applied to other applications, including health tracking for individual interest or in therapy settings.

Machine-Learning-Based Methodology for Estimation of Shoulder Load in Wheelchair-Related Activities Using Wearables.

There is a high prevalence of shoulder problems in manual wheelchair users (MWUs) with a spinal cord injury. How shoulder load relates to shoulder problems remains unclear. This study aimed to develop a machine-learning-based methodology to estimate the shoulder load in wheelchair-related activities of daily living using wearable sensors. Ten able-bodied participants equipped with five inertial measurement units (IMU) on their thorax, right arm, and wheelchair performed activities exemplary of daily life of MWUs. Electromyography (EMG) was recorded from the long head of the biceps and medial part of the deltoid. A neural network was trained to predict the shoulder load based on IMU and EMG data. Different cross-validation strategies, sensor setups, and model architectures were examined. The predicted shoulder load was compared to the shoulder load determined with musculoskeletal modeling. A subject-specific biLSTM model trained on a sparse sensor setup yielded the most promising results (mean correlation coefficient = 0.74 ± 0.14, relative root-mean-squared error = 8.93% ± 2.49%). The shoulder-load profiles had a mean similarity of 0.84 ± 0.10 over all activities. This study demonstrates the feasibility of using wearable sensors and neural networks to estimate the shoulder load in wheelchair-related activities of daily living.

Classification of Wheelchair Related Shoulder Loading Activities from Wearable Sensor Data: A Machine Learning Approach.

Shoulder problems (pain and pathology) are highly prevalent in manual wheelchair users with spinal cord injury. These problems lead to limitations in activities of daily life (ADL), labor- and leisure participation, and increase the health care costs. Shoulder problems are often associated with the long-term reliance on the upper limbs, and the accompanying "shoulder load". To make an estimation of daily shoulder load, it is crucial to know which ADL are performed and how these are executed in the free-living environment (in terms of magnitude, frequency, and duration). The aim of this study was to develop and validate methodology for the classification of wheelchair related shoulder loading ADL (SL-ADL) from wearable sensor data. Ten able bodied participants equipped with five Shimmer sensors on a wheelchair and upper extremity performed eight relevant SL-ADL. Deep learning networks using bidirectional long short-term memory networks were trained on sensor data (acceleration, gyroscope signals and EMG), using video annotated activities as the target. Overall, the trained algorithm performed well, with an accuracy of 98% and specificity of 99%. When reducing the input for training the network to data from only one sensor, the overall performance decreased to around 80% for all performance measures. The use of only forearm sensor data led to a better performance than the use of the upper arm sensor data. It can be concluded that a generalizable algorithm could be trained by a deep learning network to classify wheelchair related SL-ADL from the wearable sensor data.

Change in mobility independence over 5 years for persons with chronic spinal cord injury.

OBJECTIVES: To evaluate change in mobility independence (MI) in community dwelling persons with spinal cord injury (SCI). PARTICIPANTS: Community Survey. DESIGN: Cohort study. Rasch analysis was applied to the mobility subscale of the Spinal Cord Independence Measure - Self-Report data from years 2012 to 2017, resulting in a Rasch Mobility Independence Score (RMIS). We employed multilevel modeling to examine RMIS and its change over 5 years, adjusting for demographics and SCI severity; random forest regression was applied to determine the impact of modifiable factors (e.g. environmental factors, home-support) on its change. RESULTS: The analysis included 728 participants. The majority (≈85%) of participants demonstrated little or no change in RMIS from 2012 to 2017; however, a smaller proportion (15%) showed considerably large change of more than 10 on the 100-point scale. A mixed-effects model with random slopes and intercepts described the dataset very well (conditional R2 of 0.95) in terms of demographics and SCI severity. Age was the main predictor of change in RMIS. Considering SCI severity, change in RMIS was related to age for the subgroup with paraplegia, and to time since injury for the subgroup with tetraplegia. No impact of modifiable factors was found. CONCLUSION: RMIS in persons with SCI changes over a period of 5 years, especially in elder patients with paraplegia and persons with incomplete tetraplegia with more than 15 years of time since injury. During routine follow-up change in mobility independence should be assessed in order to timely intervene and prevent mobility loss and participation limitations.

Shoulder Pain Is Associated With Rate of Rise and Jerk of the Applied Forces During Wheelchair Propulsion in Individuals With Paraplegic Spinal Cord Injury.

OBJECTIVE: To investigate the association between propulsion biomechanics, including variables that describe smoothness of the applied forces, and shoulder pain in individuals with spinal cord injury (SCI). DESIGN: Cross-sectional, observational study. SETTING: Non-university research institution. PARTICIPANTS: Community dwelling, wheelchair dependent participants (N=30) with chronic paraplegia between T2 and L1, with and without shoulder pain (age, 48.6±9.3y; 83% men). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Rate of rise and jerk of applied forces during wheelchair propulsion. Participants were stratified in groups with low, moderate, and high pain based on their Wheelchair User Shoulder Pain Index score on the day of measurement. RESULTS: A mixed-effect multilevel analysis showed that wheelchair users in the high pain group propelled with a significantly greater rate of rise and jerk, measures that describe smoothness of the applied forces, compared with individuals with less or no pain, when controlling for all covariables. CONCLUSIONS: Individuals with severe shoulder pain propelled with less smooth strokes compared to individuals with less or no pain. This supports a possible association between shoulder pain and rate of rise and jerk of the applied forces during wheelchair propulsion.

Changes in propulsion technique and shoulder complex loading following low-intensity wheelchair practice in novices.

BACKGROUND: Up to 80% of wheelchair users are affected by shoulder pain. The Clinical Practice Guidelines for preservation of upper limb function following spinal cord injury suggest that using a proper wheelchair propulsion technique could minimize the shoulder injury risk. Yet, the exact relationship between the wheelchair propulsion technique and shoulder load is not well understood. OBJECTIVE: This study aimed to examine the changes in shoulder loading accompanying the typical changes in propulsion technique following 80 min of low-intensity wheelchair practice distributed over 3 weeks. METHODS: Seven able-bodied participants performed the pre- and the post-test and 56 min of visual feedback-based low-intensity wheelchair propulsion practice. Kinematics and kinetics of propulsion technique were recorded during the pre- and the post-test. A musculoskeletal model was used to calculate muscle force and glenohumeral reaction force. RESULTS: Participants decreased push frequency (51→36 pushes/min, p = 0.04) and increased contact angle (68→94°, p = 0.02) between the pre- and the post-test. The excursion of the upper arm increased, approaching significance (297→342 mm, p = 0.06). Range of motion of the hand, trunk and shoulder remained unchanged. The mean glenohumeral reaction force per cycle decreased by 13%, approaching significance (268→232 N, p = 0.06). CONCLUSIONS: Despite homogenous changes in propulsion technique, the kinematic solution to the task varied among the participants. Participants exhibited two glenohumeral reaction force distribution patterns: 1) Two individuals developed high force at the onset of the push, leading to increased peak and mean glenohumeral forces 2) Five individuals distributed the force more evenly over the cycle, lowering both peak and mean glenohumeral forces.

Effects of an implantable two-channel peroneal nerve stimulator versus conventional walking device on spatiotemporal parameters and kinematics of hemiparetic gait.

OBJECTIVE: The aims of this study were: (i) to compare the neuro-prosthetic effect of implantable peroneal nerve stimulation to the orthotic effect of a standard of care intervention (no device, shoe or ankle foot orthosis) on walking, as assessed by spatiotemporal parameters; and (ii) to examine whether there is evidence of an enhanced lower-limb flexion reflex with peroneal nerve stimulation and compare the kinematic effect of an implantable peroneal nerve stimulation device vs standard of care intervention on initial loading response of the paretic limb, as assessed by hip, knee and ankle kinematics. DESIGN: Randomized controlled trial. SUBJECTS: A total of 23 chronic stroke survivors with drop foot. METHODS: The intervention group received an implantable 2-channel peroneal nerve stimulator for correction of drop foot. The control group continued using a conventional walking device. Spatiotemporal parameters and hip, knee and ankle kinematics were measured while subjects walked with the device on using a 3-dimensional video camera system during baseline and after a follow-up period of 26 weeks. RESULTS: Peroneal nerve stimulation normalized stance and double support of the paretic limb and single support of the non-paretic limb, in comparison with using a conventional walking device. In addition, peroneal nerve stimulation is more effective to provide ankle dorsiflexion during swing and resulted in a normalized initial loading response. CONCLUSION: Although peroneal nerve stimulation and ankle foot orthosis are both prescribed to correct a drop foot in the same patient population, spatiotemporal parameters, dorsiflexion during swing and loading response are influenced in a functionally different way.

Effect of lifting height and load mass on low back loading.

The objective of this study was to quantify the effect of lifting height and mass lifted on the peak low back load in terms of net moments, compression forces and anterior-posterior shear forces. Ten participants had to lift a box using four handle heights. Low back loading was quantified using a dynamic 3-D linked segment model and a detailed electromyographic driven model of the trunk musculature. The effects of lifting height and lifting mass were quantified using a regression technique (GEE) for correlated data. Results indicate that an increase in lifting height and a decrease in lifting mass were related to a decrease in low back load. It is argued that trunk flexion is a major contributor to low back load. For ergonomic interventions it can be advised to prioritise optimisation of the vertical location of the load to be lifted rather than decreasing the mass of the load for handle heights between 32 cm and 155 cm, and for load masses between 7.5 and 15 kg. Lifting height and load mass are important determinants of low back load during manual materials handling. This paper provides the quantitative effect of lifting height and mass lifted, the results of which can be used by ergonomists at the workplace to evaluate interventions regarding lifting height and load mass.

Effect of job rotation on work demands, workload, and recovery of refuse truck drivers and collectors.

Job rotation is often advocated to reduce workload, but its efficacy has seldom been investigated. The aim of this study is to compare the work demands, workload, and recovery among truck driving, refuse collecting, and rotating between these two jobs, between days and during the day. Three teams of 3 employees each participated in this study. Work demands were assessed by systematic observation of tasks and activities. Workload was quantified by means of heart rate, oxygen uptake, subjective ratings, and urinary excretion rates of catecholamines. Recovery was quantified by excretion rates of catecholamines after work. Job rotation between driving and collecting is an effective measure to reduce physical workload as compared with collecting only and to decrease mental workload as compared with driving only. However, job rotation resulted in increased physical workload as compared with driving only. Job rotation did not increase mental workload as compared with collecting only. No effects were seen on recovery. No differences were found between rotating between days and during the day. Actual or potential applications of this research include the recommendation that before job rotation is introduced, its efficacy be determined in terms of well-chosen workload measures because a reduction in work demands does not directly imply a reduction in workload. Therefore, job rotation might be less effective than expected.

Mechanical loading of the low back and shoulders during pushing and pulling activities.

The objective of this study was to quantify the mechanical load on the low back and shoulders during pushing and pulling in combination with three task constraints: the use of one or two hands, three cart weights, and two handle heights. The second objective was to explore the relation between the initial and sustained exerted forces and the mechanical load on the low back and shoulders. Detailed biomechanical models of the low back and shoulder joint were used to estimate mechanical loading. Using generalized estimating equations (GEE) the effects were quantified for exerted push/pull forces, net moments at the low back and shoulders, compressive and shear forces at the low back, and compressive forces at the glenohumeral joint. The results of this study appeared to be useful to estimate ergonomics consequences of interventions in the working constraints during pushing and pulling. Cart weight as well as handle height had a considerable effect on the mechanical load and it is recommended to maintain low cart weights and to push or pull at shoulder height. Initial and sustained exerted forces were not highly correlated with the mechanical load at the low back and shoulders within the studied range of the exerted forces.

Effect of a redesigned two-wheeled container for refuse collecting on mechanical loading of low back and shoulders.

The objective of this study was to compare the mechanical and perceived workload when working with a redesigned two-wheeled container and working with a standard two-wheeled container for refuse collecting. The three changes in the design of the container were a displacement of the position of the centre of mass in the direction of the axis of the wheels, a slight increase in the height of the handle and a slight increase in the horizontal distance between the handle and the wheel-axis, and an increase in the diameter of the wheels. The volume of the container remained 0.240 m3. Nine refuse collectors performed some of their most frequent daily activities with both types of containers in the laboratory. Kinematics and exerted hand forces were assessed as input for detailed 3D biomechanical models of the low back and shoulder to estimate net moments at the low back and shoulders, compressive forces at the low back and contact forces at the glenohumeral joint. Also, the refuse collectors rated the ease of handling the two-wheeled containers on a five point scale. The use of the redesigned container resulted in a decrease of the exerted hand forces of 27%, decreases in the net moments at the low back and shoulders of 8% and 20%, respectively, and a decrease of 32% of the contact force at the glenohumeral joint when compared to the standard container. However, pulling an empty redesigned container on to the pavement resulted in an increase of the shoulder moment of more than 100%. No differences between container types were found for the compressive forces at the low back. Pushing and pulling with the redesigned container was rated as easier than pushing and pulling with the standard container. No differences in subjective ratings were found for the tasks of turning the container or pulling an empty container onto the pavement. It is concluded that, provided that empty containers are placed back onto the pavement as infrequently as possible, the introduction of the redesigned container could result in a reduction of the low back and shoulder load for refuse collectors.