@article{QuarmbyMoennigMugeleetal.2023, author = {Quarmby, Andrew and M{\"o}nnig, Jamal and Mugele, Hendrik and Henschke, Jakob and Kim, MyoungHwee and Cassel, Michael and Engel, Tilman}, title = {Biomechanics and lower limb function are altered in athletes and runners with achilles tendinopathy compared with healthy controls: A systematic review}, series = {Frontiers in Sports and Active Living}, journal = {Frontiers in Sports and Active Living}, publisher = {Frontiers}, address = {Lausanne, Schweiz}, issn = {2624-9367}, doi = {10.3389/fspor.2022.1012471}, pages = {20}, year = {2023}, abstract = {Achilles tendinopathy (AT) is a debilitating injury in athletes, especially for those engaged in repetitive stretch-shortening cycle activities. Clinical risk factors are numerous, but it has been suggested that altered biomechanics might be associated with AT. No systematic review has been conducted investigating these biomechanical alterations in specifically athletic populations. Therefore, the aim of this systematic review was to compare the lower-limb biomechanics of athletes with AT to athletically matched asymptomatic controls. Databases were searched for relevant studies investigating biomechanics during gait activities and other motor tasks such as hopping, isolated strength tasks, and reflex responses. Inclusion criteria for studies were an AT diagnosis in at least one group, cross-sectional or prospective data, at least one outcome comparing biomechanical data between an AT and healthy group, and athletic populations. Studies were excluded if patients had Achilles tendon rupture/surgery, participants reported injuries other than AT, and when only within-subject data was available.. Effect sizes (Cohen's d) with 95\% confidence intervals were calculated for relevant outcomes. The initial search yielded 4,442 studies. After screening, twenty studies (775 total participants) were synthesised, reporting on a wide range of biomechanical outcomes. Females were under-represented and patients in the AT group were three years older on average. Biomechanical alterations were identified in some studies during running, hopping, jumping, strength tasks and reflex activity. Equally, several biomechanical variables studied were not associated with AT in included studies, indicating a conflicting picture. Kinematics in AT patients appeared to be altered in the lower limb, potentially indicating a pattern of "medial collapse". Muscular activity of the calf and hips was different between groups, whereby AT patients exhibited greater calf electromyographic amplitudes despite lower plantar flexor strength. Overall, dynamic maximal strength of the plantar flexors, and isometric strength of the hips might be reduced in the AT group. This systematic review reports on several biomechanical alterations in athletes with AT. With further research, these factors could potentially form treatment targets for clinicians, although clinical approaches should take other contributing health factors into account. The studies included were of low quality, and currently no solid conclusions can be drawn.}, language = {en} } @phdthesis{Novakovic2021, author = {Novakovic, Lazar}, title = {Investigating DEFECTIVE KERNEL 1 regulation of primary cell wall biosynthesis and mechanical properties during plant growth in Arabidopsis thaliana}, school = {Universit{\"a}t Potsdam}, pages = {xxii, 213}, year = {2021}, abstract = {Plants possess cell wall, a polysaccharide exoskeleton which encompasses all plant cells. Cell wall gives plant cells mechanical support, defines their shape, enables growth and water transport through a plant. It also has important role in communication with the external environment. Regulation of plant cell wall biosynthesis and cell and organ morphogenesis depends on cell's ability to detect mechanical signals originating both from the external environment and from internal plant tissues. Thanks to the presence of the cell wall, all living plant cells develop constant internal pressure generated by the active water uptake, known as turgor pressure, which enables them to grow. Thus, actively growing cells in the tissue are exerting mechanical stress to each other. In order to properly coordinate cell growth, tissue morphogenesis and maintain cell-to-cell adhesion, plant cell have to detect these mechanical signals. That is performed by a group of still not well enough characterized plant mechanosensitive proteins. Mechanosensors are proteins capable of detecting changes in mechanical stress patterns and translating them into physiological and developmental outputs. One of plant mechanosensitive proteins, DEFECTIVE KERNEL1 (DEK1) has shown to be a very important in proper plant development. DEK1 bears similarity with animal cysteine proteases of Calpain superfamily. DEK1 is very important for plant development since all null alleles are embryo lethal. During the last 20 years of DEK1 studies, this protein has proven to be a very difficult for different molecular and biochemical manipulations. As a consequence, very little is known about its direct target proteins. Wang and co-workers (2003) and Johnson and co-workers (2008) have given a valuable contribution to biochemical understanding of DEK1 by determining that it functions as Cys-protease in similar way as animal calpains. However, a lot of indirect knowledge was gathered about the effects of disruption and modulation of DEK1 activity. DEK1 is important for proper organ development, epidermal specification, and maintenance. However, some studies have inferred that DEK1 affects expression of different cell wall related genes, and it regulates cell-to-cell adhesion in epidermal cells. This led to two extensive studies (Amanda et al., 2016, 2017) which demonstrated importance of DEK1 in regulation leaf epidermal cell walls in A. thaliana mature leaves and inflorescence stems. These studies demonstrated that DEK1 also influences cell wall thickness and cell-to-cell adhesion and that it could potentially regulate cell growth and expansion. Building up on this research, we decided to try to further characterize molecular and biomechanical aspects of DEK1 mediated cell wall regulation, with special emphasis on regulation of cellulose synthesis. We used two mutant lines, with modulated DEK1 activity, a constitutive overexpressor for DEK1 CALPAIN domain and a point mutant in CALPAIN domain, dek1-4. In Chapter 3 we demonstrated that DEK1 regulates dynamics of Cellulose Synthase Complexes (CSCs). Both lines showed decreased crystalline cellulose contents. This led us to investigate if velocity of CSCs in cotyledons, was affected, since it is known that changes in cellulose contents are often caused by defects in CSC. We found that bothDEK1 modulated lines we used have significantly decreased velocity of CSCs. We have also examined plasma membrane turnover rates of CSCs and found out that after photo-bleaching OE CALPAIN has much faster recovery rates compared to Col-0 wild type, while dek1-4 has lower exocytotic rates of CSCs, and much longer life-time of CSCs inserted into the plasma membrane. These results suggested that DEK1 regulates different aspects of CSC dynamics, possibly through interaction with different regulatory proteins. Decrease in cellulose contents we observed in DEK1 modulated lines, prompted us to investigate how this reflects biomechanics and structural properties of epidermal cotyledon cell walls of DEK1 modulated lines, which is described in Chapter 4. To achieve this, we developed a novel microdissection method for isolation and mechanical and structural characterization of native epidermal cell wall monolayers using atomic force microscopy (AFM). AFM force spectroscopy assays showed that both DEK1 modulated lines had stiffer cell walls compared to Col-0. This was awkward since we initially detected decrease in crystalline cellulose which implied decrease in cell wall stiffness. However, subsequent high-resolution AFM imaging has revealed that DEK1 modulate lines cells walls have their cellulose microfibrils organized in thicker bundles than Col-0. Also, polysaccharide composition analysis has revealed that DEK1 modulated lines have increased abundance of pectins, which could also be responsible for the observed increase in cell wall stiffness. Previous work has shown that different dek1 mutants and modulated lines have defects in cell-to-cell adhesion. This implied that DEK1 may be involved in sensing and/or maintaining cell wall integrity (CWI). We performed several growth assays to determine role of DEK1 in CWI, which is described in Chapter 5. We performed cellulose synthesis perturbation assays with cellulose synthesis inhibitor Isoxaben and obtained very interesting results. While OE CALPAIN plants were hypersensitive to Isoxaben, dek1-4 has shown complete insensitivity. Furthermore, a regular CWI maintenance response, reported in A. thaliana as result of compromised CWI, ectopic lignification in seedlings' roots was absent in both DEK1 modulated lines we examined. We detected interesting growth response of DEK1 lines to NaCl and mannitol treatments as well. Although these findings are pointing out that DEK1 could be part of CWI signalling pathways, more experiments are necessary to fully elucidate possible role of DEK1 in CWI sensing and/or maintenance pathways, especially to check if DEK1 is interacting with Catharanthus roseus Receptor Like Kinase group of CWI sensors. Studies on 4-month old short day grown DEK1 modulated lines, have shown defects in branching, with development of fasciated stem branches in a DEK1 modulated line overexpressing CALPAIN domain (Amanda et al., 2017). This result pointed out to a possibility that DEK1 may regulate organ morphogenesis and patterning at the level of shoot apical meristem (SAM). Work towards elucidating role of DEK1 in SAM maintenance and organ patterning is detailed in Chapter 6. We determined that OE CALPAIN had significantly larger central zone of SAM as well as larger individual SAM cells in central zone, as well as higher distribution of cell sizes, implying possible cell expansion defects. dek1-4 did not exhibited changes in SAM central zone size or individual stem cell size, but it seemed that it had increased number of stem cells in SAM central zone. Both DEK1 lines had perturbation of phyllotaxis on SAM level, with disturbed divergence angles between floral primordia. Disturbed phyllotaxis was also observed between siliques, in mature plants. In addition to this, OE CALPAIN has exhibited occurrence of multiple (up to four) siliques growing from a single stem node. All this is pointing out that DEK1 might participate in hormone-signalling in the SAM.. DEK1 is a highly intriguing protein. However, since it is a unigene, and in addition to that, a regulatory protease, it probably participates in multiple signalling pathways, which makes understanding its function much more complicated.}, language = {en} } @article{SandauGranacher2020, author = {Sandau, Ingo and Granacher, Urs}, title = {Effects of the barbell load on the acceleration phase during the snatch in elite Olympic weightlifting}, series = {Sports}, volume = {8}, journal = {Sports}, number = {5}, publisher = {MDPI}, address = {Basel}, issn = {2075-4663}, doi = {10.3390/sports8050059}, pages = {10}, year = {2020}, abstract = {The load-depended loss of vertical barbell velocity at the end of the acceleration phase limits the maximum weight that can be lifted. Thus, the purpose of this study was to analyze how increased barbell loads affect the vertical barbell velocity in the sub-phases of the acceleration phase during the snatch. It was hypothesized that the load-dependent velocity loss at the end of the acceleration phase is primarily associated with a velocity loss during the 1st pull. For this purpose, 14 male elite weightlifters lifted seven load-stages from 70-100\% of their personal best in the snatch. The load-velocity relationship was calculated using linear regression analysis to determine the velocity loss at 1st pull, transition, and 2nd pull. A group mean data contrast analysis revealed the highest load-dependent velocity loss for the 1st pull (t = 1.85, p = 0.044, g = 0.49 [-0.05, 1.04]) which confirmed our study hypothesis. In contrast to the group mean data, the individual athlete showed a unique response to increased loads during the acceleration sub-phases of the snatch. With the proposed method, individualized training recommendations on exercise selection and loading schemes can be derived to specifically improve the sub-phases of the snatch acceleration phase. Furthermore, the results highlight the importance of single-subject assessment when working with elite athletes in Olympic weightlifting.}, language = {en} } @phdthesis{Lesinski2019, author = {Lesinski, Melanie}, title = {Modulating factors for drop jump performance}, school = {Universit{\"a}t Potsdam}, pages = {viii, 57, xiii}, year = {2019}, abstract = {Background and objectives: Drop jumps (DJs) are well-established exercise drills during plyometric training. Several sports are performed under unstable surface conditions (e.g., soccer, beach volleyball, gymnastics). To closely mimic sport-specific demands, plyometric training includes DJs on both stable and unstable surfaces. According to the mechanical properties of the unstable surface (e.g., thickness, stiffness), altered temporal, mechanical, and physiological demands have been reported from previous cross-sectional studies compared with stable conditions. However, given that the human body simultaneously interacts with various factors (e.g., drop height, footwear, gender) during DJs on unstable surfaces, the investigation of isolated effects of unstable surface conditions might not be sufficient for designing an effective and safe DJ stimulus. Instead, the combined investigation of different factors and their interaction with surface instability have to be taken into consideration. Therefore, the present doctoral thesis seeks to complement our knowledge by examining the main and interaction effects of surface instability, drop height, footwear, and gender on DJ performance, knee joint kinematics, and neuromuscular activation. Methods: Healthy male and female physically active sports science students aged 19-26 years participated in the cross-sectional studies. Jump performance, sagittal and frontal plane knee joint kinematics, and leg muscle activity were measured during DJs on stable (i.e., firm force plate) and (highly) unstable surfaces (i.e., one or two AIREX® balance pads) from different drop heights (i.e., 20 cm, 40 cm, 60 cm) or under multiple footwear conditions (i.e., barefoot, minimal shoes, cushioned shoes). Results: Findings revealed that surface instability caused a DJ performance decline, reduced sagittal plane knee joint kinematics, and lower leg muscle activity during DJs. Sagittal plane knee joint kinematics as well as leg muscle activity decreased even more with increasing surface instability (i.e., two vs. one AIREX® balance pads). Higher (60 cm) compared to lower drop heights (≤ 40 cm) resulted in a DJ performance decline. In addition, increased sagittal plane knee joint kinematics as well as higher shank muscle activity were found during DJs from higher (60 cm) compared to lower drop heights (≤ 40 cm). Footwear properties almost exclusively affected frontal plane knee joint kinematics, indicating larger maximum knee valgus angles when performing DJs barefoot compared to shod. Between the different shoe properties (i.e., minimal vs. cushioned shoes), no significant differences during DJs were found at all. Only a few significant surface-drop height as well as surface-footwear interactions were found during DJs. They mainly indicated that drop height- and footwear-related effects are more pronounced during DJs on unstable compared to stable surfaces. In this regard, the maximum knee valgus angle was significantly greater when performing DJs from high drop heights (60 cm), but only on highly unstable surface. Further, braking and push-off times were significantly longer when performing DJs barefoot compared to shod, but only on unstable surface. Finally, analyses indicated no significant interactions with the gender factor. Conclusions: The findings of the present cumulative thesis indicate that stable rather than unstable surfaces as well as moderate (≤ 40 cm) rather than high (60 cm) drop heights provide sufficient stimuli to perform DJs. Furthermore, findings suggest that DJs on highly unstable surfaces (i.e., two AIREX® balance pads) from high drop heights (60 cm) as well as barefoot compared to shod seem to increase maximal knee valgus angle/stress by providing a more harmful DJ stimulus. Neuromuscular activation strategies appear to be modified by surface instability and drop height. However, leg muscle activity is only marginally effected by footwear and by the interactions of various external factors i.e., surface instability, drop height, footwear). Finally, gender did not significantly modulate the main or interaction effects of the observed external factors during DJs.}, language = {en} } @article{LesinskiPrieskeBordeetal.2018, author = {Lesinski, Melanie and Prieske, Olaf and Borde, Ron and Beurskens, Rainer and Granacher, Urs}, title = {Effects of Different Footwear Properties and Surface Instability on Neuromuscular Activity and Kinematics During Jumping}, series = {Journal of strength and conditioning research : the research journal of the NSCA}, volume = {32}, journal = {Journal of strength and conditioning research : the research journal of the NSCA}, number = {11}, publisher = {Lippincott Williams \& Wilkins}, address = {Philadelphia}, issn = {1064-8011}, doi = {10.1519/JSC.0000000000002556}, pages = {3246 -- 3257}, year = {2018}, abstract = {The purpose of this study was to examine sex-specific effects of different footwear properties vs. barefoot condition during the performance of drop jumps (DJs) on stable and unstable surfaces on measures of jump performance, electromyographic (EMG) activity, and knee joint kinematics. Drop jump performance, EMG activity of lower-extremity muscles, as well as sagittal and frontal knee joint kinematics were tested in 28 healthy male (n = 14) and female (n = 14) physically active sports science students (23 6 2 years) during the performance of DJs on stable and unstable surfaces using different footwear properties (elastic vs. minimal shoes) vs. barefoot condition. Analysis revealed a significantly lower jump height and performance index (Delta 7-12\%; p < 0.001; 2.22 <= d = 2.90) during DJs on unstable compared with stable surfaces. This was accompanied by lower thigh/shank muscle activities (Delta 11-28\%; p < 0.05; 0.99 <= d = 2.16) and knee flexion angles (Delta 5-8\%; p < 0.05; 1.02 <= d = 2.09). Furthermore, knee valgus angles during DJs were significantly lower when wearing shoes compared with barefoot condition (Delta 22-32\%; p < 0.01; 1.38 <= d = 3.31). Sex-specific analyses indicated higher knee flexion angles in females compared with males during DJs, irrespective of the examined surface and footwear conditions (Delta 29\%; p < 0.05; d = 0.92). Finally, hardly any significant footwear-surface interactions were detected. Our findings revealed that surface instability had an impact on DJ performance, thigh/shank muscle activity, and knee joint kinematics. In addition, the single factors "footwear" and "sex" modulated knee joint kinematics during DJs. However, hardly any significant interaction effects were found. Thus, additional footwear-related effects can be neglected when performing DJs during training on different surfaces.}, language = {en} } @article{SeiffertHolsteinSchlosseretal.2017, author = {Seiffert, Martin and Holstein, Flavio and Schlosser, Rainer and Schiller, Jochen}, title = {Next generation cooperative wearables}, series = {IEEE access : practical research, open solutions}, volume = {5}, journal = {IEEE access : practical research, open solutions}, publisher = {Institute of Electrical and Electronics Engineers}, address = {Piscataway}, issn = {2169-3536}, doi = {10.1109/ACCESS.2017.2749005}, pages = {16793 -- 16807}, year = {2017}, abstract = {Currently available wearables are usually based on a single sensor node with integrated capabilities for classifying different activities. The next generation of cooperative wearables could be able to identify not only activities, but also to evaluate them qualitatively using the data of several sensor nodes attached to the body, to provide detailed feedback for the improvement of the execution. Especially within the application domains of sports and health-care, such immediate feedback to the execution of body movements is crucial for (re-) learning and improving motor skills. To enable such systems for a broad range of activities, generalized approaches for human motion assessment within sensor networks are required. In this paper, we present a generalized trainable activity assessment chain (AAC) for the online assessment of periodic human activity within a wireless body area network. AAC evaluates the execution of separate movements of a prior trained activity on a fine-grained quality scale. We connect qualitative assessment with human knowledge by projecting the AAC on the hierarchical decomposition of motion performed by the human body as well as establishing the assessment on a kinematic evaluation of biomechanically distinct motion fragments. We evaluate AAC in a real-world setting and show that AAC successfully delimits the movements of correctly performed activity from faulty executions and provides detailed reasons for the activity assessment.}, language = {en} } @article{WippertRectorKuhnetal.2017, author = {Wippert, Pia-Maria and Rector, Michael V. and Kuhn, Gisela and Wuertz-Kozak, Karin}, title = {Stress and Alterations in Bones}, series = {Frontiers in endocrinology}, volume = {8}, journal = {Frontiers in endocrinology}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-2392}, doi = {10.3389/fendo.2017.00096}, pages = {7}, year = {2017}, abstract = {Decades of research have demonstrated that physical stress (PS) stimulates bone remodeling and affects bone structure and function through complex mechanotransduction mechanisms. Recent research has laid ground to the hypothesis that mental stress (MS) also influences bone biology, eventually leading to osteoporosis and increased bone fracture risk. These effects are likely exerted by modulation of hypothalamic-pituitary-adrenal axis activity, resulting in an altered release of growth hormones, glucocorticoids and cytokines, as demonstrated in human and animal studies. Furthermore, molecular cross talk between mental and PS is thought to exist, with either synergistic or preventative effects on bone disease progression depending on the characteristics of the applied stressor. This mini review will explain the emerging concept of MS as an important player in bone adaptation and its potential cross talk with PS by summarizing the current state of knowledge, highlighting newly evolving notions (such as intergenerational transmission of stress and its epigenetic modifications affecting bone) and proposing new research directions.}, language = {en} }