@misc{AdlerFoerstlSuessetal., author = {Adler, Ina and F{\"o}rstl, Nikolas and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Biomechanical exposition of the factors influencing the pelvic floor muscle activity}, series = {ESB 2024, 29th Congress of the European Society of Biomechanics, 30 June-3 July 2024, Edinburgh, Scotland}, journal = {ESB 2024, 29th Congress of the European Society of Biomechanics, 30 June-3 July 2024, Edinburgh, Scotland}, abstract = {Introduction About 40 \% of the women worldwide suffer from Pelvic Floor Dysfunctions [1]. In previous studies, musculoskeletal simulations helped to understand and facilitate the complex issues of musculoskeletal disorders in several different branches [2, 3]. A fundamental prerequisite for the generation of these models is to have a basic understanding of the stresses acting on the pelvic floor. The aim of this study is to investigate the biomechanical factors influencing the activity of the pelvic floor muscles by establishing a parameterised model. Methods To identify the factors that affect the pelvic floor muscles, the process is divided into several stages. The first step is to investigate the loads acting on the pelvic floor. For this, a simplified sagittal cross-sectional model of the upper body is analysed. The discretization of the abdominal cavity is presented with resulting force vectors representing the organs in the abdominal and pelvic region, the tensile force of the structures that fixate the organs as well as the intraabdominal pressure. A second step is the examination of the basic mechanics of the pelvic floor muscles. As the functional anatomy of these muscles demonstrate differences compared to other muscle groups [4], the understanding of how they differ is crucial for the construction of musculoskeletal models. After a static examination of loads on a simplified muscle model, an extended model including the physiological properties of a muscle must be involved in the considerations. Therefore, the influence of parameters such as the ideal muscle strength and fibre length, as well as elasticity or passive stiffness of the elements must be taken into account. The influencing factors of the variables can be analysed in a simplified pelvic floor muscle model by systematically changing the parameters. Results The process of analysing the factors influencing the activity of the pelvic floor muscles follows two main strategies. The review of the effects of the whole body identifies the forces acting on the pelvic floor muscles and effect their activity. With the examination of the basic mechanics of a simplified pelvic floor muscle model a better understanding is achieved of how the pelvic floor muscles absorb the loads acting in the body. Discussion This process results in the main influence factors on the activity of the pelvic floor. The consequent parameters form the basis for a biomechanically justified construction of musculoskeletal simulation models of the pelvic floor. Nevertheless, it must be considered, that these mechanical studies represent simplifications of the reality. References 1. Wang et al, Front Public Health, 10:975829, 2022. 2. Bulat et al., Curr Sports Med Rep, 18(6):210-216, 2019 3. Melzner et al., Eur J Obstet Gynecol Reprod Biol, 264:306-313, 2021 4. Ashton-Miller et al., Ann N Y Acad Sci, 1101:266-96, 2007}, language = {en} } @misc{AuerReinkerSuessetal., author = {Auer, Simon and Reinker, Lukas and S{\"u}ß, Franz and Kubowitsch, Simone and Krutsch, Werner and Weber, Markus and Renkawitz, Tobias and Dendorfer, Sebastian}, title = {Webcast: Effect of mental demand on leg loading in highly dynamic motion}, abstract = {Football players have a high risk of leg muscle injuries, especially when exposed to mental stress. Injuries to muscles of the thigh are common in amateur and professional football, representing almost a third of all injuries. These injuries occur primarily in non-contact situations and from overuse. They can lead to a range of costs, including financial costs associated with treatment as well as those associated with long-term recovery, and absence from training and/or competition. Further, there is a high risk of injury recurrence and subsequent injury.}, language = {en} } @article{FoerstlSuessEnglertetal., author = {F{\"o}rstl, Nikolas and S{\"u}ß, Franz and Englert, Carsten and Dendorfer, Sebastian}, title = {Design of a reverse shoulder implant to measure shoulder stiffness during implant component positioning}, series = {Medical Engineering \& Physics}, volume = {121}, journal = {Medical Engineering \& Physics}, edition = {Journal Pre-proof}, publisher = {Elsevier}, doi = {10.1016/j.medengphy.2023.104059}, pages = {22}, abstract = {To avoid dislocation of the shoulder joint after reverse total shoulder arthroplasty, it is important to achieve sufficient shoulder stability when placing the implant components during surgery. One parameter for assessing shoulder stability can be shoulder stiffness. The aim of this research was to develop a temporary reverse shoulder implant prototype that would allow intraoperative measurement of shoulder stiffness while varying the position of the implant components. Joint angle and torque measurement techniques were developed to determine shoulder stiffness. Hall sensors were used to measure the joint angles by converting the magnetic flux densities into angles. The accuracy of the joint angle measurements was tested using a test bench. Torques were determined by using thin-film pressure sensors. Various mechanical mechanisms for variable positioning of the implant components were integrated into the prototype. The results of the joint angle measurements showed measurement errors of less than 5° in a deflection range of ±15° adduction/abduction combined with ±45° flexion/extension. The proposed design provides a first approach for intra-operative assessment of shoulder stiffness. The findings can be used as a technological basis for further developments.}, language = {en} } @article{FoerstlAdlerSuessetal., author = {F{\"o}rstl, Nikolas and Adler, Ina and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Technologies for Evaluation of Pelvic Floor Functionality: A Systematic Review}, series = {Sensors}, volume = {24}, journal = {Sensors}, number = {12}, publisher = {MDPI}, doi = {10.3390/s24124001}, abstract = {Pelvic floor dysfunction is a common problem in women and has a negative impact on their quality of life. The aim of this review was to provide a general overview of the current state of technology used to assess pelvic floor functionality. It also provides literature research of the physiological and anatomical factors that correlate with pelvic floor health. This systematic review was conducted according to the PRISMA guidelines. The PubMed, ScienceDirect, Cochrane Library, and IEEE databases were searched for publications on sensor technology for the assessment of pelvic floor functionality. Anatomical and physiological parameters were identified through a manual search. In the systematic review, 114 publications were included. Twelve different sensor technologies were identified. Information on the obtained parameters, sensor position, test activities, and subject characteristics was prepared in tabular form from each publication. A total of 16 anatomical and physiological parameters influencing pelvic floor health were identified in 17 published studies and ranked for their statistical significance. Taken together, this review could serve as a basis for the development of novel sensors which could allow for quantifiable prevention and diagnosis, as well as particularized documentation of rehabilitation processes related to pelvic floor dysfunctions.}, language = {en} } @misc{FoerstlSuessEnglertetal., author = {F{\"o}rstl, Nikolas and S{\"u}ß, Franz and Englert, Carsten and Dendorfer, Sebastian}, title = {Design of a reverse shoulder implant to measure shoulder stiffness during implant component positioning}, series = {Book of abstracts / ESB 2023, 28th Congress of the European Society of Biomechanics, 9-12 July 2023, Maastricht, The Netherlands.}, journal = {Book of abstracts / ESB 2023, 28th Congress of the European Society of Biomechanics, 9-12 July 2023, Maastricht, The Netherlands.}, abstract = {Introduction Dislocation of the shoulder joint is one of the more common complications after reverse total shoulder arthroplasty [1], which is often associated with malposition of the prosthetic components [2]. Therefore, achieving sufficient shoulder stability should not be neglected when positioning the implant components. One parameter for assessing shoulder stability can be shoulder stiffness. The aim of this work is to develop a reverse shoulder implant prototype that allows intraoperative measurement of shoulder stiffness while varying the position of the implant components. The measured stiffness could provide a quantitative statement regarding the optimal positioning of the implant components, which can be adjusted accordingly in the final reverse shoulder prosthesis. Methods To measure the stiffness of the shoulder joint, it is necessary to record the joint angles and the torques generated during movement. The changes in the rotation angles were measured using 3D hall sensors and magnets. The magnets were placed under the humerosocket, and the hall sensors were integrated into the glenosphere. The strength of the magnetic field was used to determine the position of the humerosocket in relation to the glenosphere. The accuracies of the angle measurements were tested using a test bench. Three thin film pressure sensors were used to record forces at different points under the humerosocket. To obtain a force value from the sensor signal, the sensors were calibrated using a load cell. The variation of the implant components positions was integrated into the prototype implant through different constructive mechanisms to adjust the stiffness of the shoulder joint. Results In the range of ±45° flexion/extension combined with ±15° adduction/abduction, the joint position could be determined with sufficient accuracy (error e ≤ 5°). The areas near the combined maximum deflections of ±45° flexion/extension and ±45° adduction/abduction indicate the greatest deviation from the target angle. The force values of the thin film sensors enable the calculation of moments around two axes. As variable component position parameters, the tray offset, the neck-shaft angle and the humerus version were integrated into the implant prototype. Discussion Ideally, the accuracy of the angle measurements should only depend on the amount of deflection and not on the direction of deflection. The asymmetric behavior indicates a deviation from the correct positioning of the hall sensors. The application of a calibration matrix could compensate for the measurement errors and could demonstrate the potential of the new method for joint angle measurements. The accuracy of the torque measurements and the functionality of the mechanical arresting mechanisms must be investigated in further studies. Overall, the developed measurement method can help to avoid malpositioning of the implant components in reverse total shoulder arthroplasty. References 1. Clark et al, J Shoulder and elbow surgery, 21:36-41 2012. 2. Randelli et al, J Musculoskeletal surgery, 98:15-18, 2014.}, language = {en} } @misc{MelznerIsmailRušavyetal., author = {Melzner, Maximilian and Ismail, Khaled M. and Rušav{\´y}, Zdeněk and Kališ, Vladim{\´i}r and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Musculoskeletal Lower Back Load of Accoucheurs During Delivery}, series = {26th Congress of the European Society of Biomechanics, July 11-14, 2021, Milan, Italy}, journal = {26th Congress of the European Society of Biomechanics, July 11-14, 2021, Milan, Italy}, address = {Milan}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-20208}, abstract = {With the progress in modern medicine, it was possible to significantly reduce the risks of birth for mother and child. One aspect that has received less attention so far is the risk of injury to the accoucheurs (obstetricians and midwives) during the birth process. Indeed, studies indicate that 92\% of midwives suffer from musculoskeletal disorders, with the lower back being the main cause of complaints (72\%). The aim of this study was to investigate two commonly used postural techniques used by accoucheurs during childbirth and to analyze the resulting load on the lower back using the AnyBodyTM musculoskeletal simulation software.}, language = {en} } @article{MelznerIsmailRušavyetal., author = {Melzner, Maximilian and Ismail, Khaled M. and Rušavy, Zdenek and Kališ, Vladim{\´i}r and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Musculoskeletal lower back load of accoucheurs during childbirth - A pilot and feasibility study}, series = {European Journal of Obstetrics \& Gynecology and Reproductive Biology}, journal = {European Journal of Obstetrics \& Gynecology and Reproductive Biology}, number = {264}, publisher = {Elsevier}, doi = {10.1016/j.ejogrb.2021.07.042}, pages = {306 -- 313}, abstract = {Introduction: Back problems represent one of the leading causes of accouchers' work-related musculoskeletal morbidities. The correct execution of birth-related maneuvers including manual perineal protection is crucial not only for the mother and child but also for obstetricians and midwives to reduce any strain on their musculoskeletal system. Therefore, the overall aim of this study was to test the feasibility of determining the effect of different accouchers' postures (standing and kneeling) on their musculoskeletal system. Methods: The biomechanical analysis is based on musculoskeletal simulations that included motion recordings of real deliveries as well as deliveries conducted on a birthing simulator. These simulations were then used to determine individual joints' loads. Results: In the kneeling posture, both a low intra-operator variability and a lower average maximum load of the lower back was observed. For the standing position the spine load was reduced by pivoting the elbow on the accouchers' thigh, which in turn was associated with a significantly greater load on the shoulder joint. Conclusion: The study demonstrated the feasibility of our technique to assess joints loads. It also provided initial data indicating that a posture that reduces spinal flexion and tilt, achieved in this study by the kneeling, can significantly reduce the strain on the practitioner's musculoskeletal system.}, language = {en} } @article{BarthelSuessDendorfer, author = {Barthel, Mareike and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Application of a transformer encoder for the prediction of intra-abdominal pressure}, series = {Computer Methods in Biomechanics and Biomedical Engineering}, journal = {Computer Methods in Biomechanics and Biomedical Engineering}, publisher = {Taylor \& Francis}, doi = {10.1080/10255842.2025.2586143}, pages = {11}, abstract = {Intra-abdominal pressure is a significant physiological parameter influencing spinal stability and pelvic floor health. This study investigates the potential of a transformer encoder model to predict IAP using motion capture data and musculoskeletal modeling. Data from 211 subjects performing walking, fast walking, and running were used to train a transformer encoder. The model showed promising results with an overall Mean Absolute Percentage Error of 13.5\% and a Pearson correlation coefficient of 0.85. Predictions for fast walking and running proved to be more challenging compared to walking, which was attributed to the greater variability and complexity of faster movements.}, language = {en} } @misc{GschossmannSuessDendorfer, author = {Gschoßmann, Lukas and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Impact of Model Parameters on Ground Reaction Force Predictions in Musculoskeletal Modelling}, series = {ISB 2025 - The XXX Congress of the International Society of Biomechanics, 27-31 July, Stockholm}, journal = {ISB 2025 - The XXX Congress of the International Society of Biomechanics, 27-31 July, Stockholm}, abstract = {This study evaluated how model parameters affect ground reaction force (GRF) predictions in musculoskeletal simulations. A parameter study varying contact height and velocity thresholds and marker weights was conducted. While height and velocity thresholds had minimal impact, marker weights impact prediction errors. These findings highlight the importance of carefully selecting model parameters.}, language = {en} } @misc{FoerstlAdlerSuessetal., author = {F{\"o}rstl, Nikolas and Adler, Ina and S{\"u}ß, Franz and Jansov{\´a}, Magdalena and Vychytil, Jan and Dendorfer, Sebastian}, title = {Evaluating the loads on the female pelvic floor during full-body activities using computational models}, abstract = {This work investigated the loads on the female pelvic floor during various full-body movements using computational models to calculate abdominal pressure and organ dynamic loads. While high-impact exercises resulted in higher loads, other movements showed lower loads, potentially indicating, which movements may be performed without risking pelvic floor overload and subsequent dysfunctions.}, language = {en} } @misc{BarthelSuessDendorfer, author = {Barthel, Mareike and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Predicting intra-abdominal pressure during walking and running}, series = {ISB 2025 - The XXX Congress of the International Society of Biomechanics, 27-31. July 2025, Stockholm}, journal = {ISB 2025 - The XXX Congress of the International Society of Biomechanics, 27-31. July 2025, Stockholm}, abstract = {Intra-abdominal pressure (IAP) is an important physiological parameter, which is difficult to measure during physical activity. In this study, motion capture, musculoskeletal modeling and a transformer encoder model are used to predict IAP during walking and running. The model showed promising results with an overall mean percentage error of 13.5\% and a Pearson correlation coefficient of 0.85. Minor challenges included the lower accuracy for fast walking and running and the limited amount of data. All in all, the prediction of IAP was successful, which opens up prospects for further applications.}, language = {en} } @misc{AdlerFoerstlČechovaetal., author = {Adler, Ina and F{\"o}rstl, Nikolas and Čechov{\´a}, Hana and Nov{\´a}ček, V{\´i}t and S{\"u}ß, Franz and Dendorfer, Sebastian}, title = {Mechanistic analysis of pelvic floor functionality using musculoskeletal simulation}, series = {ISB 2025 - The XXX Congress of the International Society of Biomechanics, 27-31 July 2025, Stockholm}, journal = {ISB 2025 - The XXX Congress of the International Society of Biomechanics, 27-31 July 2025, Stockholm}, doi = {10.35096/othr/pub-8729}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-87294}, pages = {1}, abstract = {There is consensus that knowledge about the fundamentals of the pelvic floor remains incomplete, particularly regarding the sensitivity of individual pelvic floor muscles to posture variations. This study aimed to investigate the effects of variations in pelvic tilt and the point of force application induced by changes in posture on pelvic floor activity using musculoskeletal simulation. A parameter study analysed various loading cases, highlighting the coherent response of individual pelvic floor muscles to loads. Muscle activities and forces were compared across different force application points and pelvic tilt angles. A key finding was identifying peak muscle activity conditions that could help better understand the causes of pelvic floor disorders.}, language = {en} } @misc{GschossmannSchedelSuessetal., author = {Gschoßmann, Lukas and Schedel, Valentin and S{\"u}ß, Franz and Weber, Markus and Pfingsten, Andrea and Dendorfer, Sebastian}, title = {Evaluating Knee Joint Loads Across Exercises and Activities of Daily Living to Personalize TKA Rehabilitation}, series = {ISB 2025 - The XXX Congress of the International Society of Biomechanics, 27.-31. July 2025, Stockholm}, journal = {ISB 2025 - The XXX Congress of the International Society of Biomechanics, 27.-31. July 2025, Stockholm}, doi = {10.35096/othr/pub-8725}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-87252}, pages = {1}, abstract = {This study assessed knee joint loading during various physiotherapy exercises and activities of daily living in 30 healthy subjects. Results showed that lunges and squats caused the highest joint forces, while gait and stair activities also imposed substantial loads. These findings support datadriven exercise selection for personalized rehabilitation after total knee arthroplasty.}, language = {en} } @phdthesis{Suess, author = {S{\"u}ß, Franz}, title = {The influence of mental stress on the musculoskeletal human back during static posture and trunk motion}, doi = {10.5283/epub.46055}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:355-epub-460554}, pages = {106}, abstract = {The investigation of the influence of mental stress on muscle recruitment of the back and its effect on the intervertebral discs was the main focus of this work. Furthermore, the goal was to develop algorithms to use mental stress as an input parameter in musculoskeletal simulation models. In the first step, a study was designed to investigate the influence of emotional and cognitive stress without kinetic influencing factors during sitting. At the muscular level, emotional stress was found to affect the upper back, while cognitive stress elicited higher muscle activity in the upper and lower back. Using a newly developed algorithm to apply back muscle recruitment changes to static inverse kinematic simulation models, load increases at the discs of up to 189 N on average and up to 907 N at peak were found.Based on the results of the first study, a second dynamic study was designed and conducted. In this case, the focus was on the cognitive stressor and the lower back. Using a dynamometer, subject-specific loads were applied during extension and flexion of the upper back. In contrast to the first study, in the upper back, only the right m. trapezius pars descendens showed a load-induced difference in muscle activity, but the lower back did. To investigate the effects of muscle tone increase in detail, the algorithm developed in the first study was extended to the dynamic case. The use of simulation models allowed the inference of the effects of the purely stress-induced tone increase. For this purpose, the kinetic and muscular effects were isolated and simulated. The study revealed a stress increase of 47\% of the body weight in the L4L5 disc. The final numerical study focused on the general application of muscle activities to inverse kinematic simulation models. This was based on the novel simulation algorithm used in study two and the measured muscle activities. The simulation of the measured muscle activities formed the link between reality and simulation. To simulate the activities, neural networks and gradient boosting regression algorithms were investigated. The latter were found to be better suited to represent the data. However, the data is too small for a detailed statement, especially for loads below 100\%. The results of this work can help to better assess the musculoskeletal effects of psychological stress on the musculoskeletal system and, if necessary, to develop ergonomic prevention strategies. By recognizing stress-related kinematic difference, as well as subsequent prompting of trunk movement, could help prevent long-term effects. When examining any situation, the combination of machine learning and musculoskeletal simulation tools can help examine and minimize the effects of psychological stress.}, language = {en} }