The Influence of the Cervical Musculature, Visual Performance, and Anticipation on Head Impact Severity in High School and Collegiate Football

Context: Athletes with weaker, smaller, and less stiff cervical musculature; diminished visual performance; and that do not anticipate an oncoming collision are thought to be more likely to experience rapid head acceleration during collision. Objective: To compare the odds of sustaining higher magnitude head impacts between athletes with higher and lower performance on cervical characteristic and visual performance measures and to compare head impact magnitudes between anticipated and unanticipated collisions. Participants: Forty-nine high school and collegiate football players. Interventions: Participants completed the cervical testing protocol and visual performance assessment prior to the season. Video footage of on-field collisions was analyzed to determine each player's level of anticipation at the time of head impact. Head impact biomechanics were captured at each practice and game. Main Outcome Measures: Cervical muscle strength, size, and stiffness, visual performance measures, level of anticipation, and head impact biomechanical measures. Results: Football players with greater cervical stiffness had reduced odds of sustaining higher magnitude head impacts, rather than head impacts in the 1st quartile, compared to players with less cervical stiffness. Surprisingly, players with stronger and larger cervical musculature had increased odds of sustaining higher magnitude head impacts, rather than head impacts in the 1st quartile, compared to players with weaker and smaller cervical musculature. Players with better near-far quickness, target capture, and reaction time performance had increased odds of sustaining higher magnitude head impacts, rather than head impacts in the 1st quartile. Head impact biomechanical measures did not differ between anticipated and unanticipated collisions. Conclusions: Neuromuscular training aimed at enhancing cervical muscle stiffness may be useful in reducing the magnitude of head impacts sustained while playing football. The results of this study do not support the theory that players with stronger and larger cervical musculature are better able to mitigate head impact severity. Vision and level of anticipation may play less of a role than expected for protecting against higher magnitude head impacts among high school football players. In summary, cervical stiffness plays a role in mitigating head impact severity, but the roles of cervical strength, visual performance, and level of anticipation need further study.Doctor of Philosoph

LOWER EXTREMITY BIOMECHANICS OF AN ANKLE 'GIVING WAY' CASE DURING THE DROP LANDlNG

The purpose of our study was to present an accidental ankle 'giving way' case of a participant with chronic ankle instability (CAI) during drop landing test and compare lower extremity biomechanics with that of the participant's normal landing trials. A 7-camera Vicon system was used to capture motions of the participant drop landing from a 30-cm high box. Ground reaction forces were collected using two force plates. Lower extremity joint angles and moments were generated. Subjective comparisons were made between the giving way trial and normal trials. For the giving way trial, the participant exhibited greater ankle inversion, internal rotation and less hip abduction angle in pre-landing phase compared to the normal trials. In addition, the ankle exhibited greater eversion moment and external rotation moment in the landing phase. Center of pressure was more lateral in the giving way trial. We suggest that a more inverted and internally rotated ankle position before landing may place ankle at a high risk of giving way and sprain for CAI individuals

Head Impact Magnitude in American High School Football

OBJECTIVES: To describe determinants of head impact magnitudes between various play aspects in high school football. METHODS: Thirty-two high school American football players wore Head Impact Telemetry System instrumented helmets to capture head impact magnitude (linear acceleration, rotational acceleration, and Head Impact Technology severity profile [HITsp]). We captured and analyzed video from 13 games (n = 3888 viewable head impacts) to determine the following play aspects: quarter, impact cause, play type, closing distance, double head impact, player's stance, player's action, direction of gaze, athletic readiness, level of anticipation, player stationary, ball possession, receiving ball, and snapping ball. We conducted random intercepts general linear mixed models to assess the differences in head impact magnitude between play aspects (α = 0.05). RESULTS: The following aspects resulted in greater head impact magnitude: impacts during the second quarter (HITsp: P = .03); contact with another player (linear, rotational, HITsp: P < .001); initial head impact when the head is struck twice (linear, rotational, HITsp: P < .001); longer closing distances, especially when combined with a 3-point stance or when being struck in the head (linear: P = .03); the 2-point stance (linear, rotational, HITsp: P < .001); and offensive linemen not snapping the ball compared with those snapping the ball (rotational: P = .02, HITsp: P = .02). CONCLUSIONS: Preventing head impacts caused by contact with another player may reduce head impact magnitude in high school football. Rule or coaching changes that reduce collisions after long closing distances, especially when combined with the 3-point stance or when a player is being struck in the head, should be considered

Safe-Play Knowledge, Aggression, and Head-Impact Biomechanics in Adolescent Ice Hockey Players

Addressing safe-play knowledge and player aggression could potentially improve ice hockey sport safety

Age at First Concussion Influences Number of Subsequent Concussions

Background: Individuals that sustain their first concussion during childhood may be at greater risk for sustaining multiple concussions throughout their lifetime, due to a longer window of vulnerability. Purpose: To estimate the association between age at first concussion with number of subsequent concussions. Methods: A total of 23,582 collegiate athletes from 26 universities and military cadets from three military academies completed a concussion history questionnaire (65% males, age: 19.9±1.4years). Participants self-reported concussions and age at time of each injury. Participants with a history of concussion (n=3,647, 15.5%) were categorized as having sustained their first concussion during childhood (<10 years old - yo) or adolescence (≥10yo & ≤18yo). Poisson regression was used to model age group (childhood, adolescence) predicting number of subsequent concussions (0, 1, 2+). A second Poisson regression was developed to determine whether age at first concussion predicted number of subsequent concussions. Results: Participants self-reporting their first concussion during childhood had an increased risk of sustaining subsequent concussions (RR=2.19, 95% CI: 1.82, 2.64) compared to participants self-reporting their first concussion during adolescence. For every one-year increase in age at first concussion, we observed a 16% reduction in the risk of subsequent concussion (RR=0.84, 95% CI:0.82,0.86). Conclusion(s): Individuals self-reporting a concussion at a young age sustained a higher number of concussions prior to the age of 18. Concussion prevention, recognition, and reporting strategies are of particular need at the youth level

Age at First Concussion Influences Number of Subsequent Concussions

Background: Individuals that sustain their first concussion during childhood may be at greater risk for sustaining multiple concussions throughout their lifetime, due to a longer window of vulnerability. Purpose: To estimate the association between age at first concussion with number of subsequent concussions. Methods: A total of 23,582 collegiate athletes from 26 universities and military cadets from three military academies completed a concussion history questionnaire (65% males, age: 19.9±1.4years). Participants self-reported concussions and age at time of each injury. Participants with a history of concussion (n=3,647, 15.5%) were categorized as having sustained their first concussion during childhood (<10 years old - yo) or adolescence (≥10yo & ≤18yo). Poisson regression was used to model age group (childhood, adolescence) predicting number of subsequent concussions (0, 1, 2+). A second Poisson regression was developed to determine whether age at first concussion predicted number of subsequent concussions. Results: Participants self-reporting their first concussion during childhood had an increased risk of sustaining subsequent concussions (RR=2.19, 95% CI: 1.82, 2.64) compared to participants self-reporting their first concussion during adolescence. For every one-year increase in age at first concussion, we observed a 16% reduction in the risk of subsequent concussion (RR=0.84, 95% CI:0.82,0.86). Conclusion(s): Individuals self-reporting a concussion at a young age sustained a higher number of concussions prior to the age of 18. Concussion prevention, recognition, and reporting strategies are of particular need at the youth level

Estimating Contact Exposure in Football Using the Head Impact Exposure Estimate

Over the past decade, there has been significant debate regarding the effect of cumulative subconcussive head impacts on short and long-term neurological impairment. This debate remains unresolved, because valid epidemiological estimates of athletes' total contact exposure are lacking. We present a measure to estimate the total hours of contact exposure in football over the majority of an athlete's lifespan. Through a structured oral interview, former football players provided information related to primary position played and participation in games and practice contacts during the pre-season, regular season, and post-season of each year of their high school, college, and professional football careers. Spring football for college was also included. We calculated contact exposure estimates for 64 former football players (n=32 college football only, n=32 professional and college football). The head impact exposure estimate (HIEE) discriminated between individuals who stopped after college football, and individuals who played professional football (p<0.001). The HIEE measure was independent of concussion history (p=0.82). Estimating total hours of contact exposure may allow for the detection of differences between individuals with variation in subconcussive impacts, regardless of concussion history. This measure is valuable for the surveillance of subconcussive impacts and their associated potential negative effects

The JWST Resolved Stellar Populations Early Release Science Program. II. Survey Overview

We present the JWST Resolved Stellar Populations Early Release Science (ERS) program. We obtained 27.5 hr of NIRCam and NIRISS imaging of three targets in the Local Group (Milky Way globular cluster M92, ultrafaint dwarf galaxy Draco II, and star-forming dwarf galaxy WLM), which span factors of similar to 10(5) in luminosity, similar to 10(4) in distance, and similar to 10(5) in surface brightness. We describe the survey strategy, scientific and technical goals, implementation details, present select NIRCam color-magnitude diagrams (CMDs), and validate the NIRCam exposure time calculator (ETC). Our CMDs are among the deepest in existence for each class of target. They touch the theoretical hydrogen-burning limit in M92 (&lt;0.08 M-circle dot; M-F090W similar to +13.6), include the lowest-mass stars observed outside the Milky Way in Draco II (0.09M(circle dot); M-F090W similar to +12.1), and reach similar to 1.5 mag below the oldest main-sequence turnoff in WLM (M-F090W similar to +4.6). The PARSEC stellar models provide a good qualitative match to the NIRCam CMDs, though they are similar to 0.05 mag too blue compared to M92 F090W - F150W data. Our CMDs show detector-dependent color offsets ranging from similar to 0.02 mag in F090W - F150W to similar to 0.1 mag in F277W - F444W; these appear to be due to differences in the zero-point calibrations among the detectors. The NIRCam ETC (v2.0) matches the signal-to-noise ratios based on photon noise in uncrowded fields, but the ETC may not be accurate in more crowded fields, similar to what is known for the Hubble Space Telescope. We release the point-source photometry package DOLPHOT, optimized for NIRCam and NIRISS, for the community

New contributions of measurements in Europe to the global inventory of the stable isotopic composition of methane

Recent climate change mitigation strategies rely on the reduction of methane (CH4) emissions. Carbon and hydrogen isotope ratio (δ13CCH4 and δ2HCH4) measurements can be used to distinguish sources and thus to understand the CH4 budget better. The CH4 emission estimates by models are sensitive to the isotopic signatures assigned to each source category, so it is important to provide representative estimates of the different CH4 source isotopic signatures worldwide. We present new measurements of isotope signatures of various, mainly anthropogenic, CH4 sources in Europe, which represent a substantial contribution to the global dataset of source isotopic measurements from the literature, especially for δ2HCH4. They improve the definition of δ13CCH4 from waste sources, and demonstrate the use of δ2HCH4 for fossil fuel source attribution. We combined our new measurements with the last published database of CH4 isotopic signatures and with additional literature, and present a new global database. We found that microbial sources are generally well characterised. The large variability in fossil fuel isotopic compositions requires particular care in the choice of weighting criteria for the calculation of a representative global value. The global dataset could be further improved by measurements from African, South American, and Asian countries, and more measurements from pyrogenic sources. We improved the source characterisation of CH4 emissions using stable isotopes and associated uncertainty, to be used in top-down studies. We emphasise that an appropriate use of the database requires the analysis of specific parameters in relation to source type and the region of interest. The final version of the European CH4 isotope database coupled with a global inventory of fossil and non-fossil δ13CCH4 and δ2HCH4 source signature measurements is available at 10.24416/UU01-YP43IN

Relationship Between the King-Devick Test and Commonly Used Concussion Tests at Baseline

Context: Comprehensive assessments are recommended to evaluate sport-related concussion (SRC). The degree to which the King-Devick (KD) test adds novel information to an SRC evaluation is unknown. Objective: To describe relationships at baseline among the KD and other SRC assessments and explore whether the KD provides unique information to a multimodal baseline concussion assessment. Design: Cross-sectional study. Setting: Five National Collegiate Athletic Association institutions participating in the Concussion Assessment, Research and Education (CARE) Consortium. Patients or other participants: National Collegiate Athletic Association student-athletes (N = 2258, age = 20 ± 1.5 years, 53.0% male, 68.9% white) in 11 men's and 13 women's sports. Main outcome measure(s): Participants completed baseline assessments on the KD and (1) the Symptom Inventory of the Sport Concussion Assessment Tool-3rd edition, (2) the Brief Symptom Inventory-18, (3) the Balance Error Scoring System, (4) the Standardized Assessment of Concussion (SAC), (5) the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) test battery, and (6) the Vestibular/Ocular Motor Screening tool during their first year in CARE. Correlation coefficients between the KD and the 6 other concussion assessments in isolation were determined. Assessments with ρ magnitude >0.1 were included in a multivariate linear regression analysis to evaluate their relative association with the KD. Results: Scores for SAC concentration, ImPACT visual motor speed, and ImPACT reaction time were correlated with the KD (ρ = -0.216, -0.276, and 0.164, respectively) and were thus included in the regression model, which explained 16.8% of the variance in baseline KD time (P < .001, Cohen f2 = 0.20). Better SAC concentration score (β = -.174, P < .001), ImPACT visual motor speed (β = -.205, P < .001), and ImPACT reaction time (β = .056, P = .020) were associated with faster baseline KD performance, but the effect sizes were small. Conclusions: Better performance on cognitive measures involving concentration, visual motor speed, and reaction time was weakly associated with better baseline KD performance. Symptoms, psychological distress, balance, and vestibular-oculomotor provocation were unrelated to KD performance at baseline. The findings indicate limited overlap at baseline among the CARE SRC assessments and the KD