Athletic Injury Research: Frameworks, Models and the Need for Causal Knowledge.

Within applied sports science and medicine research, many challenges hinder the establishment and detailed understanding of athletic injury causality as well as the development and implementation of appropriate athletic injury prevention strategies. Applied research efforts are faced with a lack of variable control, while the capacity to compensate for this lack of control through the application of randomised controlled trials is often confronted by a number of obstacles relating to ethical or practical constraints. Such difficulties have led to a large reliance upon observational research to guide applied practice in this area. However, the reliance upon observational research, in conjunction with the general absence of supporting causal inference tools and structures, has hindered both the acquisition of causal knowledge in relation to athletic injury and the development of appropriate injury prevention strategies. Indeed, much of athletic injury research functions on a (causal) model-blind observational approach primarily driven by the existence and availability of various technologies and data, with little regard for how these technologies and their associated metrics can conceptually relate to athletic injury causality and mechanisms. In this article, a potential solution to these issues is proposed and a new model for investigating athletic injury aetiology and mechanisms, and for developing and evaluating injury prevention strategies, is presented. This solution is centred on the construction and utilisation of various causal diagrams, such as frameworks, models and causal directed acyclic graphs (DAGs), to help guide athletic injury research and prevention efforts. This approach will alleviate many of the challenges facing athletic injury research by facilitating the investigation of specific causal links, mechanisms and assumptions with appropriate scientific methods, aiding the translation of lab-based research into the applied sporting world, and guiding causal inferences from applied research efforts by establishing appropriate supporting causal structures. Further, this approach will also help guide the development and adoption of both relevant metrics (and technologies) and injury prevention strategies, as well as encourage the construction of appropriate theoretical and conceptual foundations prior to the commencement of applied injury research studies. This will help minimise the risk of resource wastage, data fishing, p-hacking and hypothesising after the results are known (HARK-ing) in athletic injury research.

A Conceptual Exploration of Hamstring Muscle-Tendon Functioning during the Late-Swing Phase of Sprinting: The Importance of Evidence-Based Hamstring Training Frameworks.

An eccentrically lengthening, energy-absorbing, brake-driven model of hamstring function during the late-swing phase of sprinting has been widely touted within the existing literature. In contrast, an isometrically contracting, spring-driven model of hamstring function has recently been proposed. This theory has gained substantial traction within the applied sporting world, influencing understandings of hamstring function while sprinting, as well as the development and adoption of certain types of hamstring-specific exercises. Across the animal kingdom, both spring- and motor-driven muscle-tendon unit (MTU) functioning are frequently observed, with both models of locomotive functioning commonly utilising some degree of active muscle lengthening to draw upon force enhancement mechanisms. However, a method to accurately assess hamstring muscle-tendon functioning when sprinting does not exist. Accordingly, the aims of this review article are three-fold: (1) to comprehensively explore current terminology, theories and models surrounding muscle-tendon functioning during locomotion, (2) to relate these models to potential hamstring function when sprinting by examining a variety of hamstring-specific research and (3) to highlight the importance of developing and utilising evidence-based frameworks to guide hamstring training in athletes required to sprint. Due to the intensity of movement, large musculotendinous stretches and high mechanical loads experienced in the hamstrings when sprinting, it is anticipated that the hamstring MTUs adopt a model of functioning that has some reliance upon active muscle lengthening and muscle actuators during this particular task. However, each individual hamstring MTU is expected to adopt various combinations of spring-, brake- and motor-driven functioning when sprinting, in accordance with their architectural arrangement and activation patterns. Muscle function is intricate and dependent upon complex interactions between musculoskeletal kinematics and kinetics, muscle activation patterns and the neuromechanical regulation of tensions and stiffness, and loads applied by the environment, among other important variables. Accordingly, hamstring function when sprinting is anticipated to be unique to this particular activity. It is therefore proposed that the adoption of hamstring-specific exercises should not be founded on unvalidated claims of replicating hamstring function when sprinting, as has been suggested in the literature. Adaptive benefits may potentially be derived from a range of hamstring-specific exercises that vary in the stimuli they provide. Therefore, a more rigorous approach is to select hamstring-specific exercises based on thoroughly constructed evidence-based frameworks surrounding the specific stimulus provided by the exercise, the accompanying adaptations elicited by the exercise, and the effects of these adaptations on hamstring functioning and injury risk mitigation when sprinting.

Understanding Training Load as Exposure and Dose.

Various terms used in sport and exercise science, and medicine, are derived from other fields such as epidemiology, pharmacology and causal inference. Conceptual and nomological frameworks have described training load as a multidimensional construct manifested by two causally related subdimensions: external and internal training load. In this article, we explain how the concepts of training load and its subdimensions can be aligned to classifications used in occupational medicine and epidemiology, where exposure can also be differentiated into external and internal dose. The meanings of terms used in epidemiology such as exposure, external dose, internal dose and dose-response are therefore explored from a causal perspective and their underlying concepts are contextualised to the physical training process. We also explain how these concepts can assist in the validation process of training load measures. Specifically, to optimise training (i.e. within a causal context), a measure of exposure should be reflective of the mediating mechanisms of the primary outcome. Additionally, understanding the difference between intermediate and surrogate outcomes allows for the correct investigation of the effects of exposure measures and their interpretation in research and applied settings. Finally, whilst the dose-response relationship can provide evidence of the validity of a measure, conceptual and computational differentiation between causal (explanatory) and non-causal (descriptive and predictive) dose-response relationships is needed. Regardless of how sophisticated or "advanced" a training load measure (and metric) appears, in a causal context, if it cannot be connected to a plausible mediator of a relevant response (outcome), it is likely of little use in practice to support and optimise the training process.

Training Load and Injury: Causal Pathways and Future Directions.

Causal pathways between training loads and the mechanisms of tissue damage and athletic injury are poorly understood. Here, the relation between specific training load measures and metrics, and causal pathways of gradual onset and traumatic injury are examined. Currently, a wide variety of internal and external training load measures and metrics exist, with many of these being commonly utilized to evaluate injury risk. These measures and metrics can conceptually be related to athletic injury through the mechanical load-response pathway, the psycho-physiological load-response pathway, or both. However, the contributions of these pathways to injury vary. Importantly, tissue fatigue damage and trauma through the mechanical load-response pathway is poorly understood. Furthermore, considerable challenges in quantifying this pathway exist within applied settings, evidenced by a notable absence of validation between current training load measures and tissue-level mechanical loads. Within this context, the accurate quantification of mechanical loads holds considerable importance for the estimation of tissue damage and the development of more thorough understandings of injury risk. Despite internal load measures of psycho-physiological load speculatively being conceptually linked to athletic injury through training intensity and the effects of psycho-physiological fatigue, these measures are likely too far removed from injury causation to provide meaningful, reliable relationships with injury. Finally, we used a common training load metric as a case study to show how the absence of a sound conceptual rationale and spurious links to causal mechanisms can disclose the weaknesses of candidate measures as tools for altering the likelihood of injuries, aiding the future development of more refined injury risk assessment methods.

Successful Outcomes of Severe COVID-19 in Patient with Chronic Lymphocytic Leukemia: Diagnostic Challenges in Immunocompromised Hosts.

The emergence and spread of 2019 novel coronavirus have led to an unprecedented public health crisis around the globe, threatening the lives of millions of people. We report a severe case of COVID-19 in a patient with chronic lymphocytic leukemia and describe primarily the clinical presentation and the challenges encountered in the COVID-19 diagnosis, treatment, and specimens sampling pitfalls. This case highlights the importance of a comprehensive diagnostic approach of pneumonia in immunocompromised hosts, including timely and safe bronchoscopy, because of the broad differential diagnosis, more challenging with the current outbreak of COVID-19.

A conceptual model and detailed framework for stress-related, strain-related, and overuse athletic injury.

A multitude of athletic injuries occur when the various tissues that make up the human body experience stresses and strains that exceed their material strength. The precise amount of stress and strain that any given tissue can withstand is determined by the mechanical properties and resultant strength of that particular tissue. These mechanical properties are directly determined by an individual's physiology and acute regulation of these properties. A number of theoretical frameworks for athletic injury occurrence have been proposed, however, a detailed conceptual framework for injury aetiology that considers the interplay between the physiological and mechanical factors and outlines the causal pathways to tissue damage and injury is needed. This will guide injury research towards a more thorough investigation of causal mechanisms and understanding of risk factors. Further, it is important to take into account the considerable differences in loading patterns which can result in varying injury outcomes such as acute stress-related, strain-related, or overuse injury. Within this article a simplified conceptual model of athletic injury is proposed along with a detailed, evidence-informed, conceptual framework for athletic injury aetiology that focuses on stress-related, strain-related, and overuse injury.

The relationship between mechanical stiffness and athletic performance markers in sub-elite footballers.

This study investigated the relationship between several measures of lower-body stiffness and physical performance variables in 22 sub-elite male football players (mean ± SD; 21.9 ± 1.5 yr; 1.79 ± 0.06 m; 72.2 ± 7.2 kg). The participants were assessed for individual muscle stiffness of the Rectus Femoris (RF), Biceps Femoris (BF) and Medial Gastrocnemius (MG) muscles and vertical stiffness (Kvert) was also assessed assessed running acceleration, maximal sprint speed, agility, vertical jumping and muscular strength. Pearson's correlations quantified the relationships and participants were also separated into relatively stiff (SG) and compliant groups (CG) for each variable. When ranked by Kvert the SG exhibited superior performance during sprinting, agility, jumping and strength (p ≤ 0.05) and when ranked by RF stiffness, SG exhibited superior sprint, agility and drop jump performance (p ≤ 0.05), while MG and BF stiffness were not related to performance. Higher stiffness appears to be beneficial to athletic performance for football players and therefore it may be beneficial for practitioners working with athletes that are required to perform dynamic activities to consider the contribution of stiffness to athletic performance.

Dispersion forces between ultracold atoms and a carbon nanotube.

Dispersion forces are long-range interactions between polarizable objects that arise from fluctuations in the electromagnetic field between them. Dispersion forces have been observed between microscopic objects such as atoms and molecules (the van der Waals interaction), between macroscopic objects (the Casimir interaction) and between an atom and a macroscopic object (the Casimir-Polder interaction). Dispersion forces are known to increase the attractive forces between the components in nanomechanical devices, to influence adsorption rates onto nanostructures, and to influence the interactions between biomolecules in biological systems. In recent years, there has been growing interest in studying dispersion forces in nanoscale systems and in exploring the interactions between carbon nanotubes and cold atoms. However, there are considerable difficulties in developing dispersion force theories for general, finite geometries such as nanostructures. Thus, there is a need for new experimental methods that are able to go beyond measurements of planar surfaces and nanoscale gratings and make measurements on isolated nanostructures. Here, we measure the dispersion force between a rubidium atom and a multiwalled carbon nanotube by inserting the nanotube into a cloud of ultracold rubidium atoms and monitoring the loss of atoms from the cloud as a function of time. We perform these experiments with both thermal clouds of ultracold atoms and with Bose-Einstein condensates. The results obtained with this approach will aid the development of theories describing quantum fields near nanostructures, and hybrid cold-atom/solid-state devices may also prove useful for applications in quantum sensing and quantum information.

Fecal M2-PK in children with Crohn's disease: a preliminary report.

BACKGROUND AND AIMS: Although active inflammatory changes in chronic Crohn's disease (CD) can be detected with serum inflammatory markers, these have low specificity and sensitivity. Stool markers of inflammation, such as M2-pyruvate kinase (M2-PK), permit more direct assessment of mucosal inflammation. The aim of this study was to assess levels of M2-PK in children with active CD and to compare to levels in healthy control children. METHODS: Fecal levels of M2-PK were measured by immunoassay using stored stool samples from children with untreated (active) CD and healthy control children. Correlations between M2-PK levels and disease activity scores and serum inflammatory markers were performed. Comparison was also made between M2PK and a second fecal inflammatory marker, S100A12. RESULTS: Mean fecal M2-PK levels were higher in the 17 patients with active CD than in the 21 healthy controls (p = 0.0007). M2-PK levels did not correlate with disease activity scores or serum inflammatory markers. There was a trend for children with ileocolonic disease to have higher levels of M2-PK in their stool compared to those with colonic disease or isolated ileal disease. Fecal M2PK did not correlate with fecal S100A12 in children with active CD. CONCLUSION: Fecal M2-PK is increased in children with active CD, indicating that this marker may be a useful non-invasive marker for gut inflammation. Further studies of M2PK are required in additional settings with larger cohorts of children with CD and with comparison to other stool markers.

Cold-atom scanning probe microscopy.

Scanning probe microscopes are widely used to study surfaces with atomic resolution in many areas of nanoscience. Ultracold atomic gases trapped in electromagnetic potentials can be used to study electromagnetic interactions between the atoms and nearby surfaces in chip-based systems. Here we demonstrate a new type of scanning probe microscope that combines these two areas of research by using an ultracold gas as the tip in a scanning probe microscope. This cold-atom scanning probe microscope offers a large scanning volume, an ultrasoft tip of well-defined shape and high purity, and sensitivity to electromagnetic forces (including dispersion forces near nanostructured surfaces). We use the cold-atom scanning probe microscope to non-destructively measure the position and height of carbon nanotube structures and individual free-standing nanotubes. Cooling the atoms in the gas to form a Bose-Einstein condensate increases the resolution of the device.

Exploiting soliton decay and phase fluctuations in atom chip interferometry of bose-einstein condensates.

We show that the decay of a soliton into vortices provides a mechanism for measuring the initial phase difference between two merging Bose-Einstein condensates. At very low temperatures, the mechanism is resonant, operating only when the clouds start in antiphase. But at higher temperatures, phase fluctuations trigger vortex production over a wide range of initial relative phase, as observed in recent experiments at MIT. Choosing the merge time to maximize the number of vortices created makes the interferometer highly sensitive to spatially varying phase patterns and hence atomic movement.

Prostatitis/chronic pelvic pain syndrome.

We review the diagnosis, categorization, and treatment of prostatitis/chronic pelvic pain syndrome based on the National Institutes of Health (NIH) classification. Prostatitis is an extremely common syndrome that afflicts 2%-10% of men. Formerly a purely clinical diagnosis, prostatitis is now classified within a complex series of syndromes (NIH category I-IV prostatitis) that vary widely in clinical presentation and response to treatment. Acute bacterial prostatitis (category I) and chronic bacterial prostatitis (category II) are characterized by uropathogenic infections of the prostate gland that respond well to antimicrobial treatment. In contrast, chronic prostatitis/chronic pelvic pain syndrome (category III), which accounts for 90%-95% of prostatitis cases, is of unknown etiology and is marked by a mixture of pain, urinary, and ejaculatory symptoms with no uniformly effective therapy. Asymptomatic inflammatory prostatitis (category IV) is an incidental finding of unknown clinical significance. This review describes the current status of prostatitis syndromes and explores the future prospects of new diagnostic tools and therapies.

Efficacy of ceftriaxone versus cefazolin in the prophylactic management of extra-articular cortical violation of bone due to low-velocity gunshot wounds.

One hundred patients sustained gunshot wounds involving bone but not joint with a low-velocity bullet. Soft-tissue involvement was less than 1 cm at its greatest diameter. All patients were free from artery or nerve damage. No formal fixation of fracture was required. The results of the study suggest that patients need not be hospitalized longer than 2 days after an extra-articular, low-velocity gunshot wound that violates the cortex. In addition, through the use of long half-life antibiotics, such as ceftriaxone, the length of hospitalization may further be reduced to a day, while the potential for morbidity from infection is not increased.

Seed survival in small myrtaceous capsules subjected to experimental heating.

Mature capsules of four small-fruited Myrtaceae (Eucalyptus regnans, Leptospermum laevigatum, L. myrsinoides and Kunzea ambigua) were heated in a muffle furnace over a range of temperatures (200-750° C) and for various lengths of time (15-300s). In addition, the rise in intracapsular temperature with time was measured at 250° C and the lethal seed temperature for K. ambigua determined by heating loose seed in a controlled-temperature water bath. Encapsulated seed survived heating for only short periods event at the lower range of experimental temperatures, with no seed surviving for more than 2 min at 200° C and the highest temperature survived being 650° C for 15 s by L. laevigatum. The species were ranked E. regnans, K. ambigua, L. myrsinoides and L. laevigatum in increasing order of insulating capacity of their capsules, based on survival times of encapsulated seed and the rate of increase of intracapsular temperatures. Seed of K. ambigua was killed when heated in water for a few seconds at 90-100° C. This result agrees closely with the threshold lethal temperature derived for all species by superimposing seed survival versus time and intracapsular temperature versus time curves for capsules heated at 250° C. These results demonstrate that despite their in situ efficacy during fire, small myrtaceous capsules hre mediocre seed insulators. They also suggest that in the field, survival times for encapsulated seed are likely to be in the order of seconds rather than minutes, which points to brief flame residence times in individual tree or shrub canopies. This work has the potential to be developed as a simple but powerful method for the measurement and mapping of fire intensities.

Improvement in catheter sepsis rate in burned children.

Routine frequent central venous catheter (CVC) changes in burned patients (either change in insertion site or change over guidewires) has been advocated to decrease catheter-related sepsis. The need for this management has not been verified for children with burns. We reviewed our pediatric burn population with regard to CVC sepsis rate and individual CVC longevity to confirm this traditional policy. From 1978 to 1988, 70 children admitted to the Children's Hospital of Oklahoma Burn Unit required central venous access. Patients in whom CVCs were changed frequently (FC), (n = 10; no. of CVC, 46) were compared with those in whom CVCs were changed only for mechanical complications or sepsis (NFC), (n = 60; no. of CVC, 74). There were 10 septic CVCs in each group. The difference in mean length of individual CVC use between FC and NFC was significant (4.6 v 17.7 days; P less than .01). The difference in the number of septic CVCs per total number of catheter days in each group was highly significant (FC: 10 CVC/212 d. = 0.05; NFC: 10 CVC/1,112 d = 0.009; P less than .001). This study demonstrates a significant decrease in catheter-related sepsis when CVCs are not changed on a routine frequent basis.

Sources of difficulty in the solution of verbal arithmetic problems by mentally retarded and nonretarded individuals.

Effects of several logical (i.e., operation type and amount of extraneous information), memory (i.e., availability of memory aids and number of problem presentations), and semantic variables (i.e., problem text type) on verbal math problem-solving performance were assessed. Results revealed that the overall problem-solving performance of mildly mentally retarded adolescents was inferior to that of nonretarded fourth graders in spite of comparable performance on a computational screening test. Although the retarded individuals experienced particular difficulty with subtraction and static problem texts, the two groups responded similarly to the other experimental variables. The possibly important role of comprehension in problem-solving was discussed.

Semantic processing can facilitate free recall in mildly retarded adolescents.

The efficacy of semantic processing in free recall was investigated in two experiments with EMR adolescents. In Experiment 1, they were taught to use one of two semantic strategies for memorizing a 15-word list. Compared with controls, neither strategy helped recall either in original learning or transfer. In Experiment 2, one of the semantic strategies, a story mnemonic, was investigated further. Rather than being taught to construct their own stories as in Experiment 1, subjects in Experiment 2 were provided with experimenter-composed stories. They showed better immediate recall and retention after 2 months than did no-strategy controls. However, about 1 year after original learning, the retention of experimental and control subjects no longer differed. Discussion focused on the story mnemonic's potential utility and the criteria for judging such potential, e.g., amount of facilitation, ease of training and performance of the strategy, and the degree of its generalizability.