Gender Differences in Head Impacts Sustained by Collegiate Ice Hockey Players

Purpose—This study aims to quantify the frequency, magnitude, and location of head impacts sustained by male and female collegiate ice hockey players over two seasons of play. Methods—Over two seasons, 88 collegiate athletes (51 female, 37 male) on two female and male NCAA varsity ice hockey teams wore instrumented helmets. Each helmet was equipped with 6 single-axis accelerometers and a miniature data acquisition system to capture and record head impacts sustained during play. Data collected from the helmets were post-processed to compute linear and rotational acceleration of the head as well as impact location. The head impact exposure data (frequency, location, and magnitude) were then compared across gender. Results—Female hockey players experienced a significantly lower (p \u3c 0.001) number of impacts per athlete exposure than males (female: 1.7 ± 0.7; male: 2.9 ± 1.2). The frequency of impacts by location was the same between gender (p \u3e 0.278) for all locations except the right side of the head, where males received fewer impacts than females (p = 0.031). Female hockey players were 1.1 times more likely than males to sustain an impact less than 50 g while males were 1.3 times more likely to sustain an impact greater than 100 g. Similarly, males were 1.9 times more likely to sustain an impact with peak rotational acceleration greater than 5,000 rad/s2 and 3.5 times more likely to sustain an impact greater than 10,000 rad/s2. Conclusions—Although the incidence of concussion has typically been higher for female hockey players than male hockey players, female players sustain fewer impacts and impacts resulting in lower head acceleration than males. Further study is required to better understand th

Educational paper: Abusive Head Trauma Part I. Clinical aspects

Abusive Head Trauma (AHT) refers to the combination of findings formerly described as shaken baby syndrome. Although these findings can be caused by shaking, it has become clear that in many cases there may have been impact trauma as well. Therefore a less specific term has been adopted by the American Academy of Pediatrics. AHT is a relatively common cause of childhood neurotrauma with an estimated incidence of 14–40 cases per 100,000 children under the age of 1 year. About 15–23% of these children die within hours or days after the incident. Studies among AHT survivors demonstrate that approximately one-third of the children are severely disabled, one-third of them are moderately disabled and one-third have no or only mild symptoms. Other publications suggest that neurological problems can occur after a symptom-free interval and that half of these children have IQs below the 10th percentile. Clinical findings are depending on the definitions used, but AHT should be considered in all children with neurological signs and symptoms especially if no or only mild trauma is described. Subdural haematomas are the most reported finding. The only feature that has been identified discriminating AHT from accidental injury is apnoea. Conclusion: AHT should be approached with a structured approach, as in any other (potentially lethal) disease. The clinician can only establish this diagnosis if he/she has knowledge of the signs and symptoms of AHT, risk factors, the differential diagnosis and which additional investigations to perform, the more so since parents seldom will describe the true state of affairs spontaneously

Agreement Between Experts and an Untrained Crowd for Identifying Dermoscopic Features Using a Gamified App: Reader Feasibility Study

Background Dermoscopy is commonly used for the evaluation of pigmented lesions, but agreement between experts for identification of dermoscopic structures is known to be relatively poor. Expert labeling of medical data is a bottleneck in the development of machine learning (ML) tools, and crowdsourcing has been demonstrated as a cost- and time-efficient method for the annotation of medical images. Objective The aim of this study is to demonstrate that crowdsourcing can be used to label basic dermoscopic structures from images of pigmented lesions with similar reliability to a group of experts. Methods First, we obtained labels of 248 images of melanocytic lesions with 31 dermoscopic “subfeatures” labeled by 20 dermoscopy experts. These were then collapsed into 6 dermoscopic “superfeatures” based on structural similarity, due to low interrater reliability (IRR): dots, globules, lines, network structures, regression structures, and vessels. These images were then used as the gold standard for the crowd study. The commercial platform DiagnosUs was used to obtain annotations from a nonexpert crowd for the presence or absence of the 6 superfeatures in each of the 248 images. We replicated this methodology with a group of 7 dermatologists to allow direct comparison with the nonexpert crowd. The Cohen κ value was used to measure agreement across raters. Results In total, we obtained 139,731 ratings of the 6 dermoscopic superfeatures from the crowd. There was relatively lower agreement for the identification of dots and globules (the median κ values were 0.526 and 0.395, respectively), whereas network structures and vessels showed the highest agreement (the median κ values were 0.581 and 0.798, respectively). This pattern was also seen among the expert raters, who had median κ values of 0.483 and 0.517 for dots and globules, respectively, and 0.758 and 0.790 for network structures and vessels. The median κ values between nonexperts and thresholded average–expert readers were 0.709 for dots, 0.719 for globules, 0.714 for lines, 0.838 for network structures, 0.818 for regression structures, and 0.728 for vessels. Conclusions This study confirmed that IRR for different dermoscopic features varied among a group of experts; a similar pattern was observed in a nonexpert crowd. There was good or excellent agreement for each of the 6 superfeatures between the crowd and the experts, highlighting the similar reliability of the crowd for labeling dermoscopic images. This confirms the feasibility and dependability of using crowdsourcing as a scalable solution to annotate large sets of dermoscopic images, with several potential clinical and educational applications, including the development of novel, explainable ML tools

Thirty Years After Michael E. Porter: What Do We Know About Business Exit?

Although a business exit is an important corporate change initiative, the buyer’s side seems to be more appealing to management researchers than the seller’s because acquisitions imply growth, i.e., success. Yet from an optimistic viewpoint, business exit can effectively create value for the selling company. In this paper we attempt to bring the relevance of the seller’s side back into our consciousness by asking: What do we know about business exit? We start our exploration with Porter (1976), focusing on literature that investigates the antecedents of, barriers to, and outcomes of business exit. We also include studies from related fields such as finance and economics.1 Through this research we determine three clusters of findings: factors promoting business exit, exit barriers, and exit outcomes. Overall, it is the intention of this paper to highlight the importance of business exit for research and practice. Knowing what we know about business exits and their high financial value we should bear in mind that exit need not mean failure but a new beginning for a corporation

Thinking about growth : a cognitive mapping approach to understanding small business development

School of Managemen

Rotational Head Kinematics in Football Impacts: An Injury Risk Function for Concussion

Recent research has suggested a possible link between sports-related concussions and neurodegen-erative processes, highlighting the importance of developing methods to accurately quantify head impact tolerance. The use of kinematic parameters of the head to predict brain injury has been sug-gested because they are indicative of the inertial response of the brain. The objective of this study is to characterize the rotational kinematics of the head associated with concussive impacts using a large head acceleration dataset collected from human subjects. The helmets of 335 football players were instrumented with accelerometer arrays that measured head acceleration following head impacts sustained during play, resulting in data for 300,977 subconcussive and 57 concussive head impacts. The average subconcussive impact had a rotational acceleration of 1230 rad/s2 and a rotational ve-locity of 5.5 rad/s, while the average concussive impact had a rotational acceleration of 5022 rad/s2 and a rotational velocity of 22.3 rad/s. An injury risk curve was developed and a nominal injury value of 6383 rad/s2 associated with 28.3 rad/s represents 50% risk of concussion. These data provide an increased understanding of the biomechanics associated with concussion, and they provide critical insight into injury mechanisms, human tolerance to mechanical stimuli, and injury prevention tech-niques

Rotational Head Kinematics in Football Impacts: An Injury Risk Function for Concussion

Recent research has suggested a possible link between sports-related concussions and neurodegen-erative processes, highlighting the importance of developing methods to accurately quantify head impact tolerance. The use of kinematic parameters of the head to predict brain injury has been sug-gested because they are indicative of the inertial response of the brain. The objective of this study is to characterize the rotational kinematics of the head associated with concussive impacts using a large head acceleration dataset collected from human subjects. The helmets of 335 football players were instrumented with accelerometer arrays that measured head acceleration following head impacts sustained during play, resulting in data for 300,977 subconcussive and 57 concussive head impacts. The average subconcussive impact had a rotational acceleration of 1230 rad/s2 and a rotational ve-locity of 5.5 rad/s, while the average concussive impact had a rotational acceleration of 5022 rad/s2 and a rotational velocity of 22.3 rad/s. An injury risk curve was developed and a nominal injury value of 6383 rad/s2 associated with 28.3 rad/s represents 50% risk of concussion. These data provide an increased understanding of the biomechanics associated with concussion, and they provide critical insight into injury mechanisms, human tolerance to mechanical stimuli, and injury prevention tech-niques

A Framework for Understanding Firms’ Foreign Exit Behavior

Although research on foreign market entry and expansion behavior has attracted significant interest in the literature, there is a general lack of research (either conceptual or empirical) on the exit behavior of international companies. To address this issue, the authors develop a conceptual framework to understand firms’ foreign exit behavior. The objective is to lay the conceptual foundation for subsequent empirical research in this area. A series of research propositions have been advanced that can guide hypothesis generation for future research

Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes

Objective: To determine whether exposure to repetitive head impacts over a single season negatively affects cognitive performance in collegiate contact sport athletes. Methods: This is a prospective cohort study at 3 Division I National Collegiate Athletic Association athletic programs. Participants were 214 Division I college varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration-time history of the head following impact, and 45 noncontact sport athletes. All athletes were assessed prior to and shortly after the season with a cognitive screening battery (ImPACT) and a subgroup of athletes also were assessed with 7 measures from a neuropsychological test battery. Results: Few cognitive differences were found between the athlete groups at the preseason or postseason assessments. However, a higher percentage of the contact sport athletes performed more poorly than predicted postseason on a measure of new learning (California Verbal Learning Test) compared to the noncontact athletes (24% vs 3.6%; p \u3c 0.006). On 2 postseason cognitive measures (ImPACT Reaction Time and Trails 4/B), poorer performance was significantly associated with higher scores on several head impact exposure metrics. Conclusion: Repetitive head impacts over the course of a single season may negatively impact learning in some collegiate athletes. Further work is needed to assess whether such effects are short term or persistent

Exploring the Role of Human Judgment in Making Discount Decisions in the Lodging Industry

This study assesses the process of making pricing decisions, specifically discounts, in the lodging industry. The study applied a qualitative technique employing structured interviews of hotel managers in the United States. The assessments included the narration of events, stages, and cycles of choices made by hotel managers. The findings of the study enhanced the understanding of how management’s discount choice was constructed. In addition, this study identified the habitual management practices in the lodging industry such as “less-than-35 rule,” “trial and error,” and “follow suit.” To confirm the findings from the interviews, a follow-up study was conducted. The survey was designed to learn what kinds of information managers rank highly when considering price adjustments in their operations. Different rankings on information attributes among departments were investigated; results show that managers from different departments rank some information elements differently. Learning the process of a discount choice provided new insights on managerial resources and capabilities required to set and change prices in the lodging industry