Identifying readiness to train: when to push and when to pull

Monitoring training load – and in particular an athlete’s ability to cope with it – is now common practice; often the data is used to define an athlete’s ‘readiness’ to train. The aim of this monitoring is to identify when athletes should be rested, when they can train as per normal, and when they can have their training load ramped up. Crudely put, this monitoring provides a ‘push or pull’ diagnosis to each athlete’s training day. In this context, push defines an increase in training load, whereas pull refers to a reduction in training load. Although the idea of implementing this is generally well accepted, the statistical approach to identifying the point of push or pull seems unstandardised and – anecdotally – varies from club to club. Therefore, presenting methods to analyse the data in this regard will be the aim of this paper. The reader can then apply justifiable and sensitive methods of data analysis to their morning measures of fatigue, such that the subsequent training session can be appropriately altered

The activity demands and physiological responses observed in professional ballet: A systematic review

The aim of this study was to systematically review research into the activity demands and physiological responses observed in professional ballet. PubMed, Web of Science, SPORTDiscus, and ProQuest were searched for original research relating to 1) the session- specific activity demands of professional ballet, 2) the general activity demands of professional ballet, 3) the immediate physiological responses to professional ballet, or 4) the delayed physiological responses to professional ballet. From an initial 7672 studies, 22 met the inclusion criteria. Methodological quality was assessed using the Mixed Methods Appraisal Tool and a modified Downs and Black Index. Professional ballet is intermittent; however, activity characteristics and intensity vary by session type and company rank. Performances involve high volumes of jumps (5.0 ± 4.9 jumps·min-1), pliés (11.7 ± 8.4 pliés·min-1), and lifts (men - 1.9 ± 3.3 lifts·min-1), which may result in near-maximal metabolic responses. Ballet classes are less metabolically intense than performance during both barre and centre ( 5 h·day-1), but half is spent at intensities below 3 METs. Evidence is mixed regarding the delayed physiological responses to professional ballet; however, metabolic and musculoskeletal adaptations are unlikely to occur from ballet alone. The mean Downs and Black score was 62%. Appraisal tools revealed that a lack of clarity regarding sampling procedures, no power calculation, and a poor quality of statistical analysis were common limitations of the included studies. Given the large working durations and high rates of jumps, pliés, and lifts, managing training loads and recovery may be a focus for strategies seeking to optimize dancer health and wellbeing. Ballet companies should provide dancers with opportunities and resources to engage in supplementary physical training. Further research is required into the physical demands of rehearsals and the longitudinal training loads undertaken by professional ballet dancers

Topological entropy and secondary folding

A convenient measure of a map or flow's chaotic action is the topological entropy. In many cases, the entropy has a homological origin: it is forced by the topology of the space. For example, in simple toral maps, the topological entropy is exactly equal to the growth induced by the map on the fundamental group of the torus. However, in many situations the numerically-computed topological entropy is greater than the bound implied by this action. We associate this gap between the bound and the true entropy with 'secondary folding': material lines undergo folding which is not homologically forced. We examine this phenomenon both for physical rod-stirring devices and toral linked twist maps, and show rigorously that for the latter secondary folds occur.Comment: 13 pages, 8 figures. pdfLaTeX with RevTeX4 macro

Lithium-Doped Two-Dimensional Perovskite Scintillator for Wide-Range Radiation Detection

Two-dimensional lead halide perovskites have demonstrated their potential as high-performance scintillators for X- and gamma-ray detection, while also being low-cost. Here we adopt lithium chemical doping in two-dimensional phenethylammonium lead bromide (PEA)2PbBr4 perovskite crystals to improve the properties and add functionalities with other radiation detections. Li doping is confirmed by X-ray photoemission spectroscopy and the scintillation mechanisms are explored via temperature dependent X-ray and thermoluminescence measurements. Our 1:1 Li-doped (PEA)2PbBr4 demonstrates a fast decay time of 11 ns (80%), a clear photopeak with an energy resolution of 12.4%, and a scintillation yield of 11,000 photons per MeV under 662 keV gamma-ray radiation. Additionally, our Li-doped crystal shows a clear alpha particle/gamma-ray discrimination and promising thermal neutron detection through 6Li enrichment. X-ray imaging pictures with (PEA)2PbBr4 are also presented. All results demonstrate the potential of Li-doped (PEA)2PbBr4 as a versatile scintillator covering a wide radiation energy range for various applications

Specialist role coaching and skill training periodisation: A football goalkeeping case study

© The Author(s) 2020. In sports like association football, professional teams are increasingly devoting resources to the role-based development of individual athletes and sub-groups. By employing ‘specialist coaches’ into athlete-support structures, clubs aim to facilitate individualised athlete training programs to enhance performance preparation as well as skill learning and talent development. Here, we discuss how contemporary pedagogical training approaches, like Nonlinear Pedagogy and the Constraints-Led approach, can enhance effectiveness of specialist role-based athlete development programs to facilitate performance functionality. We argue the need for a model of specialist role-based coaching practice in high performance sports organisations, based on a unified theoretical rationale, such as ecological dynamics. To exemplify the nature of specialist role-based coaching, a case study addresses how Nonlinear Pedagogy and Constraints-Led approach are being used for training professional football goalkeepers in an U23 years age group. Integrating key concepts from ecological dynamics, allied to principles of Nonlinear Pedagogy and the Constraints-Led approach, common skill training principles for specialist role coaches are highlighted. These illustrate the use of the recently introduced ‘Periodization of Skill Training’ framework for specialist role coaching, practically exemplifying a way to harness opportunities for performance enhancement and individualised talent development in the football goalkeeping context

Dance Exposure, Individual Characteristics, and Injury Risk over Five Seasons in a Professional Ballet Company

PURPOSE: To describe the relationships between dance exposure, dancer characteristics, and injury risk across five seasons in a professional ballet company. METHODS: Dance exposure time and clinician-reported time-loss and medical attention injury data were prospectively collected from 118 professional dancers of The Royal Ballet between 2015/16 and 2019/20. Cox proportional hazards and shared frailty models were fitted to overuse and traumatic injuries; individualized robust Z-scores for 7-day and 28-day accumulated exposure, and week-to-week change in exposure, age, sex, company rank, and injury history were included as time-varying covariates. RESULTS: Across 381,710 h of exposure, 1332 medical attention and 427 time-loss injuries were observed. Positive relationships were observed between week-to-week change in exposure and overuse time-loss (+1 Z-score hazard ratio (HR): 1.27, 95% confidence interval (CI): 1.06-1.53) and medical attention injury risk (+1 Z-score HR: 1.17, 95% CI: 1.06-1.28). A negative relationship was observed between 7-day accumulated exposure and overuse medical-attention injury risk (+1 Z-score HR: 0.74, 95% CI: 0.66-0.84). Overuse time-loss injury risk was greater in soloists compared to the corps de ballet (HR: 1.47, 95% CI: 1.01-2.15), and in dancers with a higher previous injury rate (+1 injury.1000 h-1 HR: 1.06, 95% CI: 1.02-1.10). Only age was associated with traumatic time-loss (+1-year HR: 1.05, 95% CI: 1.01-1.09) or medical attention injury risk (+1-year HR: 1.04, 95% CI: 1.01-1.07). CONCLUSION: Professional ballet companies should implement training principles such as periodization and progression, particularly in the case of senior-ranking dancers, older dancers, and dancers with high rates of previous injury. These findings provide a basis for future prospective investigations into specific causal injury pathways

Theory to Practice: Performance Preparation Models in Contemporary High-Level Sport Guided by an Ecological Dynamics Framework

Abstract: A fundamental challenge for practitioners in high-level sporting environments concerns how to support athletes in adapting behaviours to solve emergent problems during competitive performance. Guided by an ecological dynamics framework, the design and integration of competitive performance preparation models that place athlete-environment interactions at the heart of the learning process may address this challenge. This ecological conceptualisation of performance preparation signifies a shift in a coach’s role; evolving from a consistent solution provider to a learning environment designer who fosters local athlete-environment interactions. However, despite the past decades of research within the ecological dynamics framework developing an evidence-based, theoretical conceptualisation of skill acquisition, expertise and talent development, an ongoing challenge resides within its practical integration into sporting environments. This article provides two case examples in which high-level sports organisations have utilised an ecological dynamics framework for performance preparation in Australian football and Association Football. A unique perspective is offered on experiences of professional sport organisations attempting to challenge traditional ideologies for athlete performance preparation by progressing the theoretical application of ecological dynamics. These case examples intend to promote the sharing of methodological ideas to improve athlete development, affording opportunities for practitioners and applied scientists to accept, reject or adapt the approaches presented here to suit their specific ecosystems

Relativistic corrections in (gamma,N) knockout reactions

We develop a fully relativistic DWIA model for photonuclear reactions using the relativistic mean field theory for the bound state and the Pauli reduction of the scattering state which is calculated from a relativistic optical potential. Results for the 12C(gamma,p) and 16O(gamma,p) differential cross sections and photon asymmetries are displayed in a photon energy range between 60 and 257 MeV, and compared with nonrelativistic DWIA calculations. The effects of the spinor distortion and of the effective momentum approximation for the scattering state are discussed. The sensitivity of the model to different prescriptions for the one-body current operator is investigated. The off-shell ambiguities are large in (gamma,p) calculations, and even larger in (gamma,n) knockout.Comment: LaTeX2e, 18 pages, and 6 figure