Construction and evaluation of a model for wheelchair propulsion in an individual with tetraplegia

Does enforcing glenohumeral joint stability matter? A new rapid muscle redundancy solver highlights the importance of non-superficial shoulder muscles

The complexity of the human shoulder girdle enables the large mobility of the upper extremity, but also introduces instability of the glenohumeral (GH) joint. Shoulder movements are generated by coordinating large superficial and deeper stabilizing muscles spanning numerous degrees-of-freedom. How shoulder muscles are coordinated to stabilize the movement of the GH joint remains widely unknown. Musculoskeletal simulations are powerful tools to gain insights into the actions of individual muscles and particularly of those that are difficult to measure. In this study, we analyze how enforcement of GH joint stability in a musculoskeletal model affects the estimates of individual muscle activity during shoulder movements. To estimate both muscle activity and GH stability from recorded shoulder movements, we developed a Rapid Muscle Redundancy (RMR) solver to include constraints on joint reaction forces (JRFs) from a musculoskeletal model. The RMR solver yields muscle activations and joint forces by minimizing the weighted sum of squared-activations, while matching experimental motion. We implemented three new features: first, computed muscle forces include active and passive fiber contributions; second, muscle activation rates are enforced to be physiological, and third, JRFs are efficiently formulated as linear functions of activations. Muscle activity from the RMR solver without GH stability was not different from the computed muscle control (CMC) algorithm and electromyography of superficial muscles. The efficiency of the solver enabled us to test over 3600 trials sampled within the uncertainty of the experimental movements to test the differences in muscle activity with and without GH joint stability enforced. We found that enforcing GH stability significantly increases the estimated activity of the rotator cuff muscles but not of most superficial muscles. Therefore, a comparison of shoulder model muscle activity to EMG measurements of superficial muscles alone is insufficient to validate the activity of rotator cuff muscles estimated from musculoskeletal models.

Ergonomic guidelines for the design interfaces of additive modules for manual wheelchairs: sagittal plane

When designing wheelchair propulsion systems operated with the upper limb, there is a noticeable lack of ergonomic analyses informing about the areas on the wheelchair frame where hand-operated controls can be installed. With that in mind, a research goal was set to measure the areas of human hand reach within the area defined by the structural elements of a manual wheelchair. An ergonomic analysis was performed on a group of ten patients representing 50% of anthropometric dimensions. Motion capture and image analysis software based on the openCV library were used for the measurement. The conducted research resulted in the development of a map of the hands range in the lateral plane of the wheelchair, parallel to the sagittal plane. In addition, the map was divided into three zones of hand reach, taking into account various levels of comfort of hand manipulation. The total hand reach area was 1269 mm long and 731 mm high, while the most comfortable manipulation area was 352 mm long and 649 mm high. The plotted hands reach areas act as a map informing the designer where on the sagittal plane additional accessories operated by the user can be installed.

Bilateral upper extremity trunk model for cross-country sit-skiing double poling propulsion: model development and validation

The subacromial impingement syndrome is a high-incidence injury for cross-country sit-skiing skier, which is often accompanied by muscle imbalance. However, at present, no musculoskeletal model has been identified for this sport. Thus, this research aimed to establish a bilateral upper extremity trunk (BUET) musculoskeletal model suitable for cross-country sit-skiing based on OpenSim software and verify the function of the model. By splicing three existing OpenSim models, an upper limb model with 17 segments, 35 degrees of freedom, and 472 musculotendon actuators was established. The clavicle and scapula were modeled as individual bodies and then connected to the torso through a three-degrees-of-freedom rotational joint and to the clavicle through a weld joint, respectively. The five lumbar vertebrae were established separately and coupled into a three-degree-of-freedom joint. Kinematics, kinetic, and EMG signal data of five 15-s maximal effort interval tests were obtained by using seven cameras, ergometers, and surface EMG synchronous collection. Based on the resulting rotator cuff muscle geometry of the model, simulated muscle activation patterns were comparable to experimental data, and muscle-driven ability was proven. The model will be available online ( https://simtk.org/projects/bit ) for researchers to study the muscle activation of shoulder joint movement.

Musculoskeletal modelling and simulation of oil palm fresh fruit bunch harvesting

Oil palm harvesting is a labor-intensive activity and yet it was rarely investigated. Studies showed that complementing human motion analysis with musculoskeletal modelling and simulation can provide valuable information about the dynamics of the joints and muscles. Therefore, this study aims to be the first to create and evaluate an upper extremity musculoskeletal model of the oil palm harvesting motion and to assess the associated Musculoskeletal Disorder (MSD) risk. Tests were conducted at a Malaysia oil palm plantation. Six Inertial Measurement Units (IMU) and Surface Electromyography (sEMG) were used to collect kinematics of the back, shoulder and elbow joints and to measure the muscle activations of longissimus, multifidus, biceps and triceps. The simulated joint angles and muscle activations were validated against the commercial motion capture tool and sEMG, respectively. The muscle forces, joint moments and activations of rectus abdominis, iliocostalis, external oblique, internal oblique and latissimus dorsi were investigated. Findings showed that the longissimus, iliocostalis and rectus abdominis were the primary muscles relied on during harvesting. The harvesters were exposed to a higher risk of MSD while performing back flexion and back rotation. These findings provide insights into the dynamical behavior of the upper extremity muscles and joints that can potentially be used to derive ways to improve the ergonomics of oil palm harvesting, minimize the MSD risk and to design and develop assistive engineering and technological devices or tools for this activity.

In Vivo Biomechanical Assessment of a Novel Handle-Based Wheelchair Drive

Push-rim wheelchair propulsion frequently causes severe upper limb injuries in people relying on the wheelchair for ambulation. To address this problem, we developed a novel handle-based wheelchair propulsion method that follows a cyclic motion within ergonomic joint ranges of motion. The aim of this study was to measure hand propulsion forces, joint excursions and net joint torques for this novel propulsion device and to compare its performance against traditional push-rim wheelchair propulsion. We hypothesized that under similar conditions, joint excursions of this novel handle-based device will remain within their ergonomic range and that the effectiveness of the propulsion forces will be higher, leading to lower average propulsion forces compared to push-rim propulsion and reducing the risk of injury. Eight paraplegic subjects propelled the new device at two different loads on a custom-made wheelchair-based test rig. Video motion capture and force sensors were used to monitor shoulder and wrist joint kinematics and kinetics. Shoulder and wrist loads were calculated using a modified upper-extremity Wheelchair Propulsion Model available in OpenSim. The results show that with this novel propulsion device joint excursions are within their recommended ergonomic ranges, resulting in a reduced range of motion of up to 30% at the shoulder and up to 80% at the wrist, while average resultant peak forces were reduced by up to 20% compared to push-rim propulsion. Furthermore, the lower net torques at both the shoulder and wrist demonstrate the potential of this novel propulsion system to reduce the risk of upper-extremity injuries.

Wheelchair control for disabled patients using EMG/EOG based human machine interface: a review

The human-machine interface (HMI) and bio-signals have been used to control rehabilitation equipment and improve the lives of people with severe disabilities. This research depicts a review of electromyogram (EMG) or electrooculogram (EOG) signal-based control system for driving the wheelchair for disabled. For a paralysed person, EOG is one of the most useful signals that help to successfully communicate with the environment by using eye movements. In the case of amputation, the selection of muscles according to the distribution of power and frequency highly contributes to the specific motion of a wheelchair. Taking into account the day-to-day activities of persons with disabilities, both technologies are being used to design EMG or EOG based wheelchairs. This review paper examines a total of 70 EMG studies and 25 EOG studies published from 2000 to 2019. In addition, this paper covers current technologies used in wheelchair systems for signal capture, filtering, characterisation, and classification, including control commands such as left and right turns, forward and reverse motion, acceleration, deceleration, and wheelchair stop.

Muscle Contributions to Upper-Extremity Movement and Work From a Musculoskeletal Model of the Human Shoulder

Musculoskeletal models enable movement scientists to examine muscle function by computing the mechanical work done by muscles during motor tasks. To estimate muscle work accurately requires a model that is physiologically plausible. Previous models of the human shoulder have coupled scapula movement to humeral movement. While coupled movement produces a stereotypical scapulohumeral rhythm, it cannot model shrugging or independent movement of the scapula and humerus. The artificial coupling of humeral elevation to scapular rotation permits muscles that cross the glenohumeral joint, such as the rotator-cuff muscles and deltoids, to do implausible work to elevate and rotate the scapula. In reality, the motion of the scapula is controlled by thoracoscapular muscles, yet the roles of these muscles in shoulder function remains unclear. To elucidate the roles of the thoracoscapular muscles, we developed a shoulder model with an accurate scapulothoracic joint and includes scapular muscles to drive its motion. We used the model to compute the work done by the thoracoscapular muscles during shrugging and arm elevation. We found that the bulk of the work done in upper-extremity tasks is performed by the largest muscles of the shoulder: trapezius, deltoids, pectoralis major, and serratus-anterior. Trapezius and serratus anterior prove to be important synergists in performing upward-rotation of the scapula. We show that the large thoracoscapular muscles do more work than glenohumeral muscles during arm-elevation tasks. The model, experimental data and simulation results are freely available on SimTK.org to enable anyone to explore our results and to perform further studies in OpenSim 4.0.

On the influence of the shoulder kinematic chain on joint kinematics and musculotendon lengths during wheelchair propulsion estimated from multibody kinematics optimization

Multibody kinematic optimization is frequently used to assess shoulder kinematics during manual wheelchair (MWC) propulsion but multiple kinematics chains are available. It is hypothesized that these different kinematic chains affect marker tracking, shoulder kinematics and resulting musculotendon (MT) lengths. In this study, shoulder kinematics and MT lengths obtained from four shoulder kinematic chains (open-loop thorax-clavicle-scapula-humerus (M1), closed-loop with contact ellipsoid (M2), scapula rhythm from regression equations (M3), and a single ball-and- socket joint between the thorax and the humerus (M4) were compared. Right-side shoulder kinematics from seven subjects were obtained with 34 reflective markers and a scapula locator using an optoelectronic motion capture system while propelling on a MWC simulator. Data was processed based on the four models. Results showed the impact of shoulder kinematic chains on all studied variables. Marker reconstruction errors were found similar between M1 and M2 and lower than for M3 and M4. Few degrees of freedom (DoF) were noticeably different between M1 and M2, but all shoulder DoFs were significantly affected between M1 and M4. As a consequence of differences in joint kinematics, MT lengths were affected by the kinematic chain definition. The contact ellipsoid (M2) was found as a good trade-off between marker tracking and penetration avoidance of the scapula. The regression-based model (M3) was less efficient due to limited humerus elevation during MWC propulsion, as well as the ball-and-socket model (M4) which appeared not suitable for upper limbs activities, including MWC propulsion.