@article{TrounsonBuschCollieretal.2020, author = {Trounson, Karl M. and Busch, Aglaja and Collier, Neil French and Robertson, Samuel}, title = {Effects of acute wearable resistance loading on overground running lower body kinematics}, series = {PLoS one}, volume = {15}, journal = {PLoS one}, number = {12}, publisher = {PLoS}, address = {San Francisco, California, US}, issn = {1932-6203}, doi = {10.1371/journal.pone.0244361}, pages = {19}, year = {2020}, abstract = {Field-based sports require athletes to run sub-maximally over significant distances, often while contending with dynamic perturbations to preferred coordination patterns. The ability to adapt movement to maintain performance under such perturbations appears to be trainable through exposure to task variability, which encourages movement variability. The aim of the present study was to investigate the extent to which various wearable resistance loading magnitudes alter coordination and induce movement variability during running. To investigate this, 14 participants (three female and 11 male) performed 10 sub-maximal velocity shuttle runs with either no weight, 1\%, 3\%, or 5\% of body weight attached to the lower limbs. Sagittal plane lower limb joint kinematics from one complete stride cycle in each run were assessed using functional data analysis techniques, both across the participant group and within-individuals. At the group-level, decreases in ankle plantarflexion following toe-off were evident in the 3\% and 5\% conditions, while increased knee flexion occurred during weight acceptance in the 5\% condition compared with unloaded running. At the individual-level, between-run joint angle profiles varied, with six participants exhibiting increased joint angle variability in one or more loading conditions compared with unloaded running. Loading of 5\% decreased between-run ankle joint variability among two individuals, likely in accordance with the need to manage increased system load or the novelty of the task. In terms of joint coordination, the most considerable alterations to coordination occurred in the 5\% loading condition at the hip-knee joint pair, however, only a minority of participants exhibited this tendency. Coaches should prescribe wearable resistance individually to perturb preferred coordination patterns and encourage movement variability without loading to the extent that movement options become limited.}, language = {en} } @article{NegraChaabeneSammoudetal.2020, author = {Negra, Yassine and Chaabene, Helmi and Sammoud, Senda and Prieske, Olaf and Moran, Jason and Ramirez-Campillo, Rodrigo and Nejmaoui, Ali and Granacher, Urs}, title = {The increased effectiveness of loaded versus unloaded plyometric jump training in improving muscle power, speed, change of direction, and kicking-distance performance in prepubertal male soccer players}, series = {International journal of sports physiology and performance : IJSSP}, volume = {15}, journal = {International journal of sports physiology and performance : IJSSP}, number = {2}, publisher = {Human Kinetics}, address = {Champaign, Ill.}, issn = {1555-0265}, doi = {10.1123/ijspp.2018-0866}, pages = {189 -- 195}, year = {2020}, abstract = {Purpose: To examine the effects of loaded (LPJT) versus unloaded plyometric jump training (UPJT) programs on measures of muscle power, speed, change of direction (CoD), and kicking-distance performance in prepubertal male soccer players. Methods: Participants (N = 29) were randomly assigned to a LPJT group (n = 13; age = 13.0 [0.7] y) using weighted vests or UPJT group (n = 16; age = 13.0 [0.5] y) using body mass only. Before and after the intervention, tests for the assessment of proxies of muscle power (ie, countermovement jump, standing long jump); speed (ie, 5-, 10-, and 20-m sprint); CoD (ie, Illinois CoD test, modified 505 agility test); and kicking-distance were conducted. Data were analyzed using magnitude-based inferences. Results: Within-group analyses for the LPJT group showed large and very large improvements for 10-m sprint time (effect size [ES] = 2.00) and modified 505 CoD (ES = 2.83) tests, respectively. For the same group, moderate improvements were observed for the Illinois CoD test (ES = 0.61), 5- and 20-m sprint time test (ES = 1.00 for both the tests), countermovement jump test (ES = 1.00), and the maximal kicking-distance test (ES = 0.90). Small enhancements in the standing long jump test (ES = 0.50) were apparent. Regarding the UPJT group, small improvements were observed for all tests (ES = 0.33-0.57), except 5- and 10-m sprint time (ES = 1.00 and 0.63, respectively). Between-group analyses favored the LPJT group for the modified 505 CoD (ES = 0.61), standing long jump (ES = 0.50), and maximal kicking-distance tests (ES = 0.57), but not for the 5-m sprint time test (ES = 1.00). Only trivial between-group differences were shown for the remaining tests (ES = 0.00-0.09). Conclusion: Overall, LPJT appears to be more effective than UPJT in improving measures of muscle power, speed, CoD, and kicking-distance performance in prepubertal male soccer players.}, 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} } @article{LesinskiSchmelcherHerzetal.2020, author = {Lesinski, Melanie and Schmelcher, Alina and Herz, Michael and Puta, Christian and Gabriel, Holger and Arampatzis, Adamantios and Laube, Gunnar and B{\"u}sch, Dirk and Granacher, Urs}, title = {Maturation-, age-, and sex-specific anthropometric and physical fitness percentiles of German elite young athletes}, series = {Plos One}, volume = {15}, journal = {Plos One}, number = {8}, publisher = {Plos One}, address = {San Francisco, California}, issn = {1932-6203}, doi = {10.1371/journal.pone.0237423}, pages = {19}, year = {2020}, abstract = {The aim of this study was to establish maturation-, age-, and sex-specific anthropometric and physical fitness percentile reference values of young elite athletes from various sports. Anthropometric (i.e., standing and sitting body height, body mass, body mass index) and physical fitness (i.e., countermovement jump, drop jump, change-of-direction speed [i.e., T-test], trunk muscle endurance [i.e., ventral Bourban test], dynamic lower limbs balance [i.e., Y-balance test], hand grip strength) of 703 male and female elite young athletes aged 8-18 years were collected to aggregate reference values according to maturation, age, and sex. Findings indicate that body height and mass were significantly higher (p<0.001; 0.95≤d≤1.74) in more compared to less mature young athletes as well as with increasing chronological age (p<0.05; 0.66≤d≤3.13). Furthermore, male young athletes were significantly taller and heavier compared to their female counterparts (p<0.001; 0.34≤d≤0.50). In terms of physical fitness, post-pubertal athletes showed better countermovement jump, drop jump, change-of-direction, and handgrip strength performances (p<0.001; 1.57≤d≤8.72) compared to pubertal athletes. Further, countermovement jump, drop jump, change-of-direction, and handgrip strength performances increased with increasing chronological age (p<0.05; 0.29≤d≤4.13). In addition, male athletes outperformed their female counterpart in the countermovement jump, drop jump, change-of-direction, and handgrip strength (p<0.05; 0.17≤d≤0.76). Significant age by sex interactions indicate that sex-specific differences were even more pronounced with increasing age. Conclusively, body height, body mass, and physical fitness increased with increasing maturational status and chronological age. Sex-specific differences appear to be larger as youth grow older. Practitioners can use the percentile values as approximate benchmarks for talent identification and development.}, language = {en} } @article{GhahremaniGieseVogel2020, author = {Ghahremani, Sona and Giese, Holger and Vogel, Thomas}, title = {Improving scalability and reward of utility-driven self-healing for large dynamic architectures}, series = {ACM transactions on autonomous and adaptive systems}, volume = {14}, journal = {ACM transactions on autonomous and adaptive systems}, number = {3}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {1556-4665}, doi = {10.1145/3380965}, pages = {41}, year = {2020}, abstract = {Self-adaptation can be realized in various ways. Rule-based approaches prescribe the adaptation to be executed if the system or environment satisfies certain conditions. They result in scalable solutions but often with merely satisfying adaptation decisions. In contrast, utility-driven approaches determine optimal decisions by using an often costly optimization, which typically does not scale for large problems. We propose a rule-based and utility-driven adaptation scheme that achieves the benefits of both directions such that the adaptation decisions are optimal, whereas the computation scales by avoiding an expensive optimization. We use this adaptation scheme for architecture-based self-healing of large software systems. For this purpose, we define the utility for large dynamic architectures of such systems based on patterns that define issues the self-healing must address. Moreover, we use pattern-based adaptation rules to resolve these issues. Using a pattern-based scheme to define the utility and adaptation rules allows us to compute the impact of each rule application on the overall utility and to realize an incremental and efficient utility-driven self-healing. In addition to formally analyzing the computational effort and optimality of the proposed scheme, we thoroughly demonstrate its scalability and optimality in terms of reward in comparative experiments with a static rule-based approach as a baseline and a utility-driven approach using a constraint solver. These experiments are based on different failure profiles derived from real-world failure logs. We also investigate the impact of different failure profile characteristics on the scalability and reward to evaluate the robustness of the different approaches.}, language = {en} } @article{GhahremaniGiese2020, author = {Ghahremani, Sona and Giese, Holger}, title = {Evaluation of self-healing systems}, series = {Computers}, volume = {9}, journal = {Computers}, number = {1}, publisher = {MDPI}, address = {Basel}, issn = {2073-431X}, doi = {10.3390/computers9010016}, pages = {32}, year = {2020}, abstract = {Evaluating the performance of self-adaptive systems is challenging due to their interactions with often highly dynamic environments. In the specific case of self-healing systems, the performance evaluations of self-healing approaches and their parameter tuning rely on the considered characteristics of failure occurrences and the resulting interactions with the self-healing actions. In this paper, we first study the state-of-the-art for evaluating the performances of self-healing systems by means of a systematic literature review. We provide a classification of different input types for such systems and analyse the limitations of each input type. A main finding is that the employed inputs are often not sophisticated regarding the considered characteristics for failure occurrences. To further study the impact of the identified limitations, we present experiments demonstrating that wrong assumptions regarding the characteristics of the failure occurrences can result in large performance prediction errors, disadvantageous design-time decisions concerning the selection of alternative self-healing approaches, and disadvantageous deployment-time decisions concerning parameter tuning. Furthermore, the experiments indicate that employing multiple alternative input characteristics can help with reducing the risk of premature disadvantageous design-time decisions.}, language = {en} } @article{VaidSomaniRussaketal.2020, author = {Vaid, Akhil and Somani, Sulaiman and Russak, Adam J. and De Freitas, Jessica K. and Chaudhry, Fayzan F. and Paranjpe, Ishan and Johnson, Kipp W. and Lee, Samuel J. and Miotto, Riccardo and Richter, Felix and Zhao, Shan and Beckmann, Noam D. and Naik, Nidhi and Kia, Arash and Timsina, Prem and Lala, Anuradha and Paranjpe, Manish and Golden, Eddye and Danieletto, Matteo and Singh, Manbir and Meyer, Dara and O'Reilly, Paul F. and Huckins, Laura and Kovatch, Patricia and Finkelstein, Joseph and Freeman, Robert M. and Argulian, Edgar and Kasarskis, Andrew and Percha, Bethany and Aberg, Judith A. and Bagiella, Emilia and Horowitz, Carol R. and Murphy, Barbara and Nestler, Eric J. and Schadt, Eric E. and Cho, Judy H. and Cordon-Cardo, Carlos and Fuster, Valentin and Charney, Dennis S. and Reich, David L. and B{\"o}ttinger, Erwin and Levin, Matthew A. and Narula, Jagat and Fayad, Zahi A. and Just, Allan C. and Charney, Alexander W. and Nadkarni, Girish N. and Glicksberg, Benjamin S.}, title = {Machine learning to predict mortality and critical events in a cohort of patients with COVID-19 in New York City: model development and validation}, series = {Journal of medical internet research : international scientific journal for medical research, information and communication on the internet ; JMIR}, volume = {22}, journal = {Journal of medical internet research : international scientific journal for medical research, information and communication on the internet ; JMIR}, number = {11}, publisher = {Healthcare World}, address = {Richmond, Va.}, issn = {1439-4456}, doi = {10.2196/24018}, pages = {19}, year = {2020}, abstract = {Background: COVID-19 has infected millions of people worldwide and is responsible for several hundred thousand fatalities. The COVID-19 pandemic has necessitated thoughtful resource allocation and early identification of high-risk patients. However, effective methods to meet these needs are lacking. Objective: The aims of this study were to analyze the electronic health records (EHRs) of patients who tested positive for COVID-19 and were admitted to hospitals in the Mount Sinai Health System in New York City; to develop machine learning models for making predictions about the hospital course of the patients over clinically meaningful time horizons based on patient characteristics at admission; and to assess the performance of these models at multiple hospitals and time points. Methods: We used Extreme Gradient Boosting (XGBoost) and baseline comparator models to predict in-hospital mortality and critical events at time windows of 3, 5, 7, and 10 days from admission. Our study population included harmonized EHR data from five hospitals in New York City for 4098 COVID-19-positive patients admitted from March 15 to May 22, 2020. The models were first trained on patients from a single hospital (n=1514) before or on May 1, externally validated on patients from four other hospitals (n=2201) before or on May 1, and prospectively validated on all patients after May 1 (n=383). Finally, we established model interpretability to identify and rank variables that drive model predictions. Results: Upon cross-validation, the XGBoost classifier outperformed baseline models, with an area under the receiver operating characteristic curve (AUC-ROC) for mortality of 0.89 at 3 days, 0.85 at 5 and 7 days, and 0.84 at 10 days. XGBoost also performed well for critical event prediction, with an AUC-ROC of 0.80 at 3 days, 0.79 at 5 days, 0.80 at 7 days, and 0.81 at 10 days. In external validation, XGBoost achieved an AUC-ROC of 0.88 at 3 days, 0.86 at 5 days, 0.86 at 7 days, and 0.84 at 10 days for mortality prediction. Similarly, the unimputed XGBoost model achieved an AUC-ROC of 0.78 at 3 days, 0.79 at 5 days, 0.80 at 7 days, and 0.81 at 10 days. Trends in performance on prospective validation sets were similar. At 7 days, acute kidney injury on admission, elevated LDH, tachypnea, and hyperglycemia were the strongest drivers of critical event prediction, while higher age, anion gap, and C-reactive protein were the strongest drivers of mortality prediction. Conclusions: We externally and prospectively trained and validated machine learning models for mortality and critical events for patients with COVID-19 at different time horizons. These models identified at-risk patients and uncovered underlying relationships that predicted outcomes.}, language = {en} } @article{WerfelliHammamiSelmietal.2021, author = {Werfelli, Hanen and Hammami, Raouf and Selmi, Mohamed Amine and Selmi, Walid and Gabrilo, Goran and Clark, Cain C. T. and Duncan, Michael and Sekulic, Damir and Granacher, Urs and Rebai, Haithem}, title = {Acute Effects of Different Plyometric and Strength Exercises on Balance Performance in Youth Weightlifters}, series = {Frontiers in Physiology}, volume = {12}, journal = {Frontiers in Physiology}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-042X}, doi = {10.3389/fphys.2021.716981}, pages = {9}, year = {2021}, abstract = {Background: High-intensity muscle actions have the potential to temporarily improve the performance which has been denoted as postactivation performance enhancement. Objectives: This study determined the acute effects of different stretch-shortening (fast vs. low) and strength (dynamic vs. isometric) exercises executed during one training session on subsequent balance performance in youth weightlifters. Materials and Methods: Sixteen male and female young weightlifters, aged 11.3±0.6years, performed four strength exercise conditions in randomized order, including dynamic strength (DYN; 3 sets of 3 repetitions of 10 RM) and isometric strength exercises (ISOM; 3 sets of maintaining 3s of 10 RM of back-squat), as well as fast (FSSC; 3 sets of 3 repetitions of 20-cm drop-jumps) and slow (SSSC; 3 sets of 3 hurdle jumps over a 20-cm obstacle) stretch-shortening cycle protocols. Balance performance was tested before and after each of the four exercise conditions in bipedal stance on an unstable surface (i.e., BOSU ball with flat side facing up) using two dependent variables, i.e., center of pressure surface area (CoP SA) and velocity (CoP V). Results: There was a significant effect of time on CoP SA and CoP V [F(1,60)=54.37, d=1.88, p<0.0001; F(1,60)=9.07, d=0.77, p=0.003]. In addition, a statistically significant effect of condition on CoP SA and CoP V [F(3,60)=11.81, d=1.53, p<0.0001; F(3,60)=7.36, d=1.21, p=0.0003] was observed. Statistically significant condition-by-time interactions were found for the balance parameters CoP SA (p<0.003, d=0.54) and CoP V (p<0.002, d=0.70). Specific to contrast analysis, all specified hypotheses were tested and demonstrated that FSSC yielded significantly greater improvements than all other conditions in CoP SA and CoP V [p<0.0001 (d=1.55); p=0.0004 (d=1.19), respectively]. In addition, FSSC yielded significantly greater improvements compared with the two conditions for both balance parameters [p<0.0001 (d=2.03); p<0.0001 (d=1.45)]. Conclusion: Fast stretch-shortening cycle exercises appear to be more effective to improve short-term balance performance in young weightlifters. Due to the importance of balance for overall competitive achievement in weightlifting, it is recommended that young weightlifters implement dynamic plyometric exercises in the fast stretch-shortening cycle during the warm-up to improve their balance performance.}, language = {en} } @article{SommererSquatritoTallbergetal.2021, author = {Sommerer, Thomas and Squatrito, Theresa and Tallberg, Jonas and Lundgren, Magnus}, title = {Decision-making in international organizations}, series = {The review of international organizations}, volume = {17}, journal = {The review of international organizations}, number = {4}, publisher = {Springer}, address = {Boston}, issn = {1559-7431}, doi = {10.1007/s11558-021-09445-x}, pages = {815 -- 845}, year = {2021}, abstract = {International organizations (IOs) experience significant variation in their decision-making performance, or the extent to which they produce policy output. While some IOs are efficient decision-making machineries, others are plagued by deadlock. How can such variation be explained? Examining this question, the article makes three central contributions. First, we approach performance by looking at IO decision-making in terms of policy output and introduce an original measure of decision-making performance that captures annual growth rates in IO output. Second, we offer a novel theoretical explanation for decision-making performance. This account highlights the role of institutional design, pointing to how majoritarian decision rules, delegation of authority to supranational institutions, and access for transnational actors (TNAs) interact to affect decision-making. Third, we offer the first comparative assessment of the decision-making performance of IOs. While previous literature addresses single IOs, we explore decision-making across a broad spectrum of 30 IOs from 1980 to 2011. Our analysis indicates that IO decision-making performance varies across and within IOs. We find broad support for our theoretical account, showing the combined effect of institutional design features in shaping decision-making performance. Notably, TNA access has a positive effect on decision-making performance when pooling is greater, and delegation has a positive effect when TNA access is higher. We also find that pooling has an independent, positive effect on decision-making performance. All-in-all, these findings suggest that the institutional design of IOs matters for their decision-making performance, primarily in more complex ways than expected in earlier research.}, language = {en} } @article{UrbachFay2021, author = {Urbach, Tina and Fay, Doris}, title = {Leader member exchange in leaders' support for voice}, series = {Applied psychology : an international review}, volume = {70}, journal = {Applied psychology : an international review}, number = {2}, publisher = {Wiley}, address = {Hoboken}, issn = {0269-994X}, doi = {10.1111/apps.12245}, pages = {674 -- 708}, year = {2021}, abstract = {While previous research underscores the role of leaders in stimulating employee voice behaviour, comparatively little is known about what affects leaders' support for such constructive but potentially threatening employee behaviours. We introduce leader member exchange quality (LMX) as a central predictor of leaders' support for employees' ideas for constructive change. Apart from a general benefit of high LMX for leaders' idea support, we propose that high LMX is particularly critical to leaders' idea support if the idea voiced by an employee constitutes a power threat to the leader. We investigate leaders' attribution of prosocial and egoistic employee intentions as mediators of these effects. Hypotheses were tested in a quasi-experimental vignette study (N = 160), in which leaders evaluated a simulated employee idea, and a field study (N = 133), in which leaders evaluated an idea that had been voiced to them at work. Results show an indirect effect of LMX on leaders' idea support via attributed prosocial intentions but not via attributed egoistic intentions, and a buffering effect of high LMX on the negative effect of power threat on leaders' idea support. Results differed across studies with regard to the main effect of LMX on idea support.}, language = {en} }