Head Impact Exposure and Mechanisms in Female High School Lacrosse via an Instrumented Mouthguard

ObjectiveTo quantify the head impact biomechanics, by impact mechanism, of female high school lacrosse players during games using an instrumented mouthguard.BackgroundThere is growing concern for the neurologic effects of repetitive head impacts in sports, which have been linked with several short-term neurophysiologic deficits. Girls' lacrosse represents a popular but understudied sport with regard to head impact exposure and current debate exists as to the need for enhanced protective equipment.Design/MethodsA female high school varsity lacrosse team wore the Stanford Instrumented Mouthguard during competitive games for the 2019 season. Video footage was reviewed to confirm head impact events and remove false-positive recordings. For each impact event, the mechanism was coded as stick contact, player contact, fall, or ball contact. Head impact rates were calculated per athlete exposure (AE, defined as a single player participating in a single game).ResultsSensor data were recorded for 15 female varsity lacrosse players for 14 games and 97 AEs. During games, 31 sensor-recorded head impacts were video-confirmed resulting in a pooled average head impact rate of 0.32 impacts/AE. The video-confirmed impacts were distributed between stick contact (17, 54.8%), player contact (12, 38.7%), and falls (2, 6.5%). There were no ball impacts. Overall peak kinematics were 34.0 ± 26.6 g, 12.0 ± 9.1 rad/s, and 3,666.5 ± 2,987.6 rad/s2. Stick contacts had the highest peak linear acceleration (42.7 ± 32.2 g), angular velocity (14.5 ± 11.1 rad/s), and angular acceleration (4,242.4 ± 3,634.9 rad/s2).ConclusionsStick impacts were the most common impact mechanism and resulted in the highest peak linear and angular kinematics, which may help explain why they are the most common cause of head injury in female lacrosse. By quantifying the head impact exposure, kinematics and mechanisms in female high school lacrosse, targeted injury preventions can be developed, such as rule changes and protective equipment.

The effect of grassland transfer on herders' livestock production and grazing intensity in Inner Mongolia and Gansu, China

Purpose The purpose of this study is to understand the impact mechanism of grassland transfer on herders' production behaviour in pastoral areas. The impact of grassland transfer on herders' livestock production and grazing intensity is quantified.Design/methodology/approach Using the survey data collected for 356 herder households from Inner Mongolia and Gansu, China, quantile regression is employed to assess the heterogeneous effects of grassland transfer on livestock production and grazing intensity. To correct the potential self-selection bias of grassland transfer, the propensity score matching technique is used.Findings Results show that labour, percentage of livestock income and livestock stock are the main factors affecting herders' choice to transfer grassland. The positive effect of grassland transfer on livestock numbers on behalf of those who rented additional grassland is statistically significant but declines with livestock numbers. The sustainability-enhancing effect of grassland transfer on grazing intensity is significant, and the effect becomes larger amongst herder households with higher grazing intensity. The analysis on the impact mechanism shows that grassland transfer significantly promotes the adoption of sustainable grazing modes, such as rotational and seasonal rest grazing, which in turn increases herders' livestock numbers and decreases grazing intensity.Originality/value Few studies have empirically analysed the influence of grassland transfer on livestock numbers and grazing intensity. This study fills this gap by employing a quantile regression to assess the heterogeneous effects of grassland transfer on livestock numbers and grazing intensity, while accounting for self-selection bias. In addition, the authors have examined the influencing mechanisms under which grassland transfer impacts on livestock numbers and grazing intensity.

The Spillover Effect of Labor Agglomeration on Regional Economic Growth

Under the background that China's labor force is decreasing and they can move freely, this paper selects the Spatial Doberman model with time-individual fixed effects to analyze and study the spatial spillover effect and its impact mechanism of the labor agglomeration of 31 provinces in mainland China from 2003 to 2018 on regional economic growth. It was found that in China, the increase in the concentration of labor in a region and surrounding areas can promote economic growth in the region through the increase in marketization and the decline in the dependency ratio. However, the current regional economic growth in China is manifested by the promotion of labor agglomeration in the region and the suppression of labor agglomeration in the surrounding areas.

Determinants of Green Regeneration of Industrial Brownfield under Ecological Security Constraints: Model and Empirical Analysis Based on Grounded Theory

Green regeneration of industrial brownfields (GRIB) is an inevitable choice under the collision of industrial structure adjustment and ecological civilization construction. Due to vegetation destruction and industrial pollution, the integrity and health of the ecosystem in the industrial brownfield have been destroyed and ecological security has become a primary factor in restricting GRIB. In order to explore the impact mechanism of GRIB under ecological security constraints, based on the original data obtained from in-depth interviews with 21 professionals, this study examines the applicability of DPSIR model in GRIB by using the grounded theory method to sort the determinants and explore the impact mechanism of GRIB under ecological security constraints from five dimensions: driving forces (incentive factor), pressure (external factor), state (internal factor), influence (produced comprehensive result), and response (substantive response of human society). Suggestions are made to strengthen the investigation and remediation of environmental pollution in industrial brownfield, cultivate the concept and awareness of green regeneration, and formulate incentive policies. The research conclusions effectively improve the problems existing in the reconstruction of industrial brownfield as well as provide a theoretical basis and targeted reference for the promotion of GRIB.