11:30   Upper extremities Chair: Alessio Murgia The Study of Relationship Between Muscle Activation and Deformation During Arm Motion Bangyu Lan, Kenan Niu Abstract: Understanding the relationship between muscle activation and deformation is critical for muscle contraction dynamics analysis, which is used in muscle disease (FSHD) diagnostic or certain muscle therapy protocol evaluation. Current research mainly focuses on intermediate muscle characteristics, such as torque, arm forces, and movement prediction, to establish the connections between these characteristics and the muscle activation or muscle thickness deformation. There is less research discussing the direct relationship between muscle activation and deformation, which is a more fundamental and important topic. In this study, we collected two types of bio-signals corresponding to muscle deformation and activation from the subject’s arm movement and built the deep-learning models to separately classify the motion’s type. With the results, the correlation between muscle activation and deformation can be demonstrated. Six subjects were recruited to participate in the experiment for collecting the bio-signals, namely muscle activation (by sEMG) and muscle deformation (by A-mode ultrasound). The sEMG signals collected the generated motor unit action potentials from muscle contractions, while the ultrasound signals recorded the bone movement, which was later processed to get the muscle thickness deformation. These two devices were attached on the right arm of subjects closed to the elbow joint. After wearing the devices, the subjects began to lift their arms (motion 1) and put them down (motion 2) for one motion cycle, which was repeated for 5 mins to finish the bio-signals recording. The collected signals were then pre-processed to be classified into two motion types via the proposed attention UNet. We first pre-train the classification models using five-subject datasets, then fine-tune and evaluate the models on the rest one-subject dataset. This was performed for each of subjects. The classification accuracy was 90% for ultrasound and 70% for sEMG. Although the large difference of the accuracy, these two classification sequences had clear correlations validated by the chi-square significance test (P-value<0.05), showing the relationship between muscle activation and deformation. Thus, through our experiments we demonstrated the important relationship between muscle activation and thickness deformation, which paved the way for further functional analysis and applications of the muscle contraction dynamics. A 3D-printed arm for venipuncture training Michelle van den Boorn, Amy Hofman, Sonja Gerber, Vera Lagerburg, Susan . G. Brouwer de Koning Abstract: Background: The venipuncture is one of the most frequently performed procedures in healthcare. Arm phantoms are available for training because the procedure itself can be challenging. These phantom arms do not represent a realistic setting and do not offer opportunities to train challenging scenarios. The objective of this randomized, single-blind study was to train healthcare workers on both a commercially available injection arm and an in-house developed 3D-printed arm and to evaluate the perceived realism and adequacy of training on both arms. Methods: Participants were trained on both the commercially available arm (A) and the 3D-printed arm (B). Participants were blinded from knowing which arm they started training on. A questionnaire was filled in on, amongst others, the perceived realism of the arm (0 for not realistic, 100 for realistic) and adequacy of the training (inadequate, moderate, adequate). Results: A total of 68 participants evaluated the perceived realism of arm A and B, which were on average 62.97 (SD 21.47) and 63.79 (SD 17.45), respectively. The difference in perceived realism of the two arms was not statistically significant (p=0.784). Training on arm A was reported inadequate by 7.4% of the participants, moderately adequate by 30.9% and adequate by 61.8%. This was not significantly different from arm B (p=0.739), with 4.4%, 38.2% and 57.4%, respectively Conclusions: The 3D-printed arm is as realistic and provides an equally adequate training compared to the commercially available arm. The 3D-printed arm offers the additional possibility to design different models representing several levels of difficulty for vascular morphology. This potentially lowers the number of venipuncture failures by preparing healthcare workers on challenging scenarios. Quantifying co-contraction in selected agonist-antagonist muscles in persons with muscle dystrophy performing functional tasks using an arm support Alessio Murgia, Kenneth Meijer, Johannes Essers Abstract: Facioscapulohumeral dystrophy (FSHD) results in progressive upper extremity muscle weakness and fatigue. Dynamic arm supports (DASs) help regain function but could introduce higher agonist-antagonist muscle co-contractions that could lead to less available joint torque, greater joint stiffness and energy expenditure. In this study, we investigated the effect of DAS on co-contraction of scapular stabilizers and humeral mobilizers during functional tasks. We hypothesized that the FSHD population would present higher co-contraction compared to the unsupported condition. Electromyograms (EMG) of upper extremity muscles were recorded in twelve FSHD participants (6M/6F, 56.0±14.5yrs, 1.76±0.10m, 75±20kg) during maximum voluntary contractions (MVC) and a contralateral reaching task with/without DAS: The Gowing (Focal Meditech BV, The Netherlands). The co-contraction index (CI), as defined by Rudolph et al. 2000 (Knee Surg., Sport Traumatol. Arthrosc.), was calculated for the rectified, MVC-normalized, low-passed (5 Hz) EMG linear envelopes of two agonist-antagonist pairs: trapezius ascendens-serratus anterior (T-S) and deltoid medial-latissimus dorsi (D-L). The CI values were calculated as average values and for every normalized time point (0-100%). Two Wilcoxon signed-rank tests, for T-S and D-L pairs respectively, were performed on the average CI without vs. with support (alpha=0.025). Effect size was calculated as Hedge’s g. Results showed that average CI decreased for D-L (p: 0.02, ΔCI: -0.03, Hedge’s g: -0.76 to -0.48), but not for T-S (p: 0.33, ΔCI: -0.01, Hedge’s g: -0.19 to -0.13) pair when using the DAS. The CI varied over time during the task, as a response to the non-linear load imposed by the DAS and the dynamic nature of the task. Contrary to our hypothesis, co-contraction decreased in D-L and was not altered in the T-S pair when using a DAS. Therefore, the DAS had a beneficial effect by partially reducing joint stiffness, which is a consequence of agonist-antagonist co-contraction, and that was initially expected since the DAS applies an upward force on the forearm. These results are relevant for designing DAS that can adapt to the user’s strength profile and further reduce fatigue and energy expenditure. In future research, musculoskeletal modelling could provide insights into joint forces to interpret changes in co-contraction responses over time. Open-loop system identification of intrinsic and reflexive impedance of the elbow joint Karien ter Welle, Alfred Schouten, Winfred Mugge, Arno Stienen, Mark van de Ruit Abstract: In Upper Motor Neuron Lesion (UMNL) following stroke, patients can experience increased joint impedance, resisting joint rotation and hindering functional movement. This heightened impedance in UMNL is driven by both exaggerated reflexes and increased intrinsic muscle activation through co-contraction, hypertonus, or synergies [1]. The simultaneous presence of these mechanisms complicates clinical distinction. Separate quantification of this intrinsic and reflexive impedance and their interaction, can aid in further investigation of the pathophysiology of post-stroke joint impairment and clinical decision making [2]. The current study presents the investigation of using robotic perturbations and an Open-Loop System Identification (sysID) protocol, to separately quantify intrinsic and reflexive impedance of the elbow joint. An experiment was performed in which 16 healthy participants were asked to maintain different levels of elbow flexion torque (0%, 10%, to 30% of maximum voluntary contraction) while receiving multisine rotational joint perturbations. Multiple perturbation signals were used, differing in bandwidth and power but with a maximum amplitude of 2°. An impedance model consisting of both intrinsic and reflexive parameters was fit to the estimated frequency response function (FRF), relating perturbation angle to elbow joint torque. The experiments showed that increased muscle activation increased both the intrinsic joint impedance and the reflex velocity gain. Both the velocity and frequency content of the different used perturbation signals had no influence on the identified joint response. These findings confirm the expected relationship between muscle activation and intrinsic impedance, as well as the theorised interplay between intrinsic activation and the reflex response [3]. However, the lack of differences found for the different perturbation signals does not align with findings of reflex suppression during high-bandwidth force perturbations [4] and during high-velocity binary or unidirectional joint stretches [5]. This work forms a starting point for further research, showing the capability of this sysID technique to separate intrinsic and reflexive joint impedance. Simultaneously it shows the need for further investigation of the effect of task instructions and perturbation signals on the identified impedance parameters, emphasizing the need to align the experimental design with the clinical question at hand. [1] C. Trompetto et al., “Pathophysiology of spasticity: implications for neurorehabilitation,” BioMed Res. Int., vol. 2014, p. 354906, 2014, doi: 10.1155/2014/354906. [2] C. G. M. Meskers, J. H. de Groot, E. de Vlugt, and A. C. Schouten, “NeuroControl of movement: system identification approach for clinical benefit,” Front. Integr. Neurosci., vol. 9, p. 48, 2015, doi: 10.3389/fnint.2015.00048. [3] J. G. McPherson, A. H. Stienen, J. M. Drogos, and J. P. Dewald, “Modification of Spastic Stretch Reflexes at the Elbow by Flexion Synergy Expression in Individuals With Chronic Hemiparetic Stroke,” Arch. Phys. Med. Rehabil., vol. 99, no. 3, Art. no. 3, Mar. 2018, doi: 10.1016/j.apmr.2017.06.019. [4] F. C. T. van der Helm, A. C. Schouten, E. de Vlugt, and G. G. Brouwn, “Identification of intrinsic and reflexive components of human arm dynamics during postural control,” J. Neurosci. Methods, vol. 119, no. 1, Art. no. 1, Sep. 2002, doi: 10.1016/S0165-0270(02)00147-4. [5] A. Klomp, E. de Vlugt, J. H. de Groot, C. G. M. Meskers, J. H. Arendzen, and F. C. T. van der Helm, “Perturbation velocity affects linearly estimated neuromechanical wrist joint properties,” J. Biomech., vol. 74, pp. 207–212, Jun. 2018, doi: 10.1016/j.jbiomech.2018.04.007. Quantifying the Risk of Elbow Prosthesis Failure: A Biomechanical Analysis of Joint Loading Roos G.A. Duijn, Danielle Meijering, Riemer J.K. Vegter, Alexander L. Boerboom, Denise Eygendaal, Martin Stevens, Claudine J.C. Lamoth, Alessio Murgia Abstract: Background: Total elbow arthroplasty (TEA) is a surgical intervention used to treat various elbow pathologies. Overloading of the prosthetic elbow joint, particularly in the varus-valgus (VV) direction, is recognized as a primary cause of failure. Additionally, high loads in the flexion-extension (FE) direction could lead to material wear and further deformation. Therefore, it is relevant to understand how VV loads and FE power generation are altered in individuals with TEA during the execution of daily tasks. Objective: To investigate differences in FE range of motion (ROM), VV joint moments, and FE power generation during eight activities of daily living (ADLs) between TEA patients and healthy controls. We hypothesized differences in both VV moments and FE power between the groups. Methods: Seven TEA patients and 18 healthy controls performed eight simulated ADL tasks. Elbow FE ROM, VV joint moments, power generation, and work were quantified using musculoskeletal modelling software (OpenSim). A mixed-model statistical design was used to analyze group differences and task-specific variations. Results: TEA patients exhibited reduced FE ROM (60.6° ± 25.6 vs. 44.9° ± 19.9, p = 0.003) and lower VV joint moments and peak power during the chair-rising task (FE moment: 5.7 Nm vs. 14.5 Nm, p = 0.026; peak power: 3.6 Watts vs. 20.1 Watts, p = 0.036). While no overall group effect was found for joint work, task-specific differences in execution were observed. TEA patients demonstrated increased joint work during the cup-emptying task, likely due to longer movement times. Conclusions: The results reveal differences in VV joint moments and power generation during specific ADLs between healthy individuals and TEA patients, with the observed adaptations potentially explained by reduced triceps strength and altered FE ROM in the TEA patients. The findings underscore the importance of considering both FE and VV loads in understanding prosthesis failure and the mechanical challenges faced by TEA patients. These insights are crucial for improving implant survival rates by informing more effective rehabilitation strategies and optimizing prosthesis design to better withstand the biomechanical demands placed on the joint. Robotic assessment of stroke: The Shoulder Elbow Perturbator Jonathan van Zanten, Winfred Mugge, Arno Stienen Abstract: Physicians use assessment scales such as the Modified Ashworth Scale to assess the motor impairment of stroke patients. However, the results of these scales are subjective and cannot differentiate the underlying cause of the motor impairment. Robotic assessment of motor impairment combined with system identification provides an objective measurement tool to differentiate between the joint's intrinsic and reflective properties. These properties accurately measure muscle weakness, spasticity, abnormal synergy, or joint viscoelasticity. The Shoulder Elbow Perturbator (SEP) allows physicians to acquire this improved measure to create an optimised treatment plan and track a patient's progress during treatment. The research line's objective is that this leads to a faster or enhanced patient recovery. Previous studies, including those by van der Velden et al., demonstrated the performance and clinical relevance of the SEP for both conventional and system identification protocols. These findings support the SEP’s potential for broader clinical application. The controller of the SEP was improved and extended, making it possible to transition smoothly from admittance control to velocity control. This contributes to more accurate measurements and a reduction in testing time. The SEP will be extended to assess other joints, and an affordable version will be designed to make the clinical application possible. We invite discussion on these developments and welcome the opportunity to explore additional directions.

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