Evaluating the psychometric properties of the Grit scale in Marine recruits using Rasch analysis.

INTRODUCTION: Successful completion of initial military training has been suggested to be predicted by physical abilities, cognitive abilities and non-cognitive abilities such as hardiness and grit. This study aimed to assess the psychometric properties of a Dutch version of a grit measurement scale: the NL-Grit scale. METHODS: We assessed the factor structure, unidimensionality of the subscales, discriminative quality of the rating scale and investigated to what extend the items together can reliably measure the entire range of grit levels in Dutch Marine recruits. We used data of Marine recruit training platoons of the Royal Netherlands Marine Corps. RESULTS: Principal component analysis reflected two subscales: 'consistency of interests' and 'perseverance of effort'. Rasch analysis confirmed the unidimensionality of the intended subscales. Rasch rating scale analysis indicated that the five-point response scale was not used as intended by respondents. Disordered rating scale categories were collapsed to obtain ordered rating categories. The item and person parameters (grit levels) largely overlapped, indicating that the item spread was sufficient for measuring the entire range of grit trait levels. However, larger gaps between item location parameters suggested a low discriminative capacity of the NL-Grit scale for respondents with trait levels within the gaps. CONCLUSION: Our evaluation of the NL-Grit scale suggests sound psychometric quality of the NL-Grit in Dutch Marine recruits. Reliability could be improved by adding items to fill the observed gaps in item content.

One out of four recruits drops out from elite military training due to musculoskeletal injuries in the Netherlands Armed Forces.

INTRODUCTION: Musculoskeletal injuries (MSIs) are among the main causes of dropout from military training. The main purpose of this study was to provide an overview of dropout rates and MSI incidence rates during elite military training. Second, this study aimed to explore restricted training days due to MSIs and to describe MSI-care by military physicians. METHODS: In a retrospective observational study, we collected dropout rates and injury surveillance data from the electronic patient records of two elite units of the Netherlands Armed Forces (NAF): the Royal Netherlands Marine Corps (RNLMC) and the Airmobile Brigade (AMB), from 1 January 2015 until 31 December 2017. RESULTS: In the RNLMC, total dropout rate was 53.9% and dropout due to MSIs was 23%. The most frequently affected locations were foot, knee and leg. In the AMB total dropout rate was 52.6% and dropout due to MSIs was 25%. In the AMB, the most frequently affected locations were back, knee and leg. Average restricted training days due to MSIs ranged between 8.3 and 20.8 days/injury. MSI-care by military physicians consisted mostly of the provision of injury-specific information and (self-)management options, imposing a specific activity restriction and referral to physiotherapy. CONCLUSION: Our study findings showed that one out of four recruits who dropout from elite military training in the NAF, do so due to MSIs. Redesigning training programmes with the objective to reduce MSIs should be given high priority, as this may reduce dropout substantially.

Development and Validation of a Dynamically Updated Prediction Model for Attrition From Marine Recruit Training.

ABSTRACT: Dijksma, I, Hof, MHP, Lucas, C, and Stuiver, MM. Development and validation of a dynamically updated prediction model for attrition from Marine recruit training. J Strength Cond Res 36(9): 2523-2529, 2022-Whether fresh Marine recruits thrive and complete military training programs, or fail to complete, is dependent on numerous interwoven variables. This study aimed to derive a prediction model for dynamically updated estimation of conditional dropout probabilities for Marine recruit training. We undertook a landmarking analysis in a Cox proportional hazard model using longitudinal data from 744 recruits from existing databases of the Marine Training Center in the Netherlands. The model provides personalized estimates of dropout from Marine recruit training given a recruit's baseline characteristics and time-varying mental and physical health status, using 21 predictors. We defined nonoverlapping landmarks at each week and developed a supermodel by stacking the landmark data sets. The final supermodel contained all but one a priori selected baseline variables and time-varying health status to predict the hazard of attrition from Marine recruit training for each landmark as comprehensive as possible. The discriminative ability (c-index) of the prediction model was 0.78, 0.75, and 0.73 in week one, week 4 and week 12, respectively. We used 10-fold cross-validation to train and evaluate the model. We conclude that this prediction model may help to identify recruits at an increased risk of attrition from training throughout the Marine recruit training and warrants further validation and updates for other military settings.

Grit was not associated to dropout in Dutch Marine recruits.

Approximately half of all recruits drop out of Marine recruit training. Identifying associated and predisposing factors for dropout would be helpful to understand dropout patterns and induce preventive strategies. Grit has been suggested to be a predictor of who is likely to succeed and who is not. We aimed to investigate the association between baseline grit scores and dropout of Marine recruit training in the Netherlands Armed Forces. We performed an exploratory study using data of three platoons Marine recruit training of the Royal Netherlands Marine Corps. Individual grit levels were measured using the NL-Grit scale, including two subscales. The primary outcome of this study was successful completion or dropout of Marine recruit training. Data were available from 270 recruits, of whom 119 (44%) dropped out of training. The odds ratio for dropout were 1.01 (95% CI 0.84-1.21, p = .917) and 1.07 (95% CI 0.89-1.29, p = .481) per standard deviation increase of consistency of interests and perseverance of effort, respectively. Our study did not confirm the proposed association between baseline grit levels and dropout of Marine recruit training in Dutch Marine recruits using the NL-Grit scale.

Nonexercise Interventions for Prevention of Musculoskeletal Injuries in Armed Forces: A Systematic Review and Meta-Analysis.

CONTEXT: This study evaluates the effect of nonexercise interventions on the reduction of risk for musculoskeletal injuries in armed forces. EVIDENCE ACQUISITION: A database search was conducted in PubMed/MEDLINE, Embase, Cochrane Library, CINAHL, SPORTdiscus, Greylit, Open Grey, the WHO trial registry, and the reference lists of included articles up to July 2019. RCTs and cluster RCTs evaluating nonexercise interventions for the prevention of musculoskeletal injuries in armed forces compared with any other intervention(s) or no intervention were eligible for inclusion. Data extraction and risk of bias assessment were done by 2 authors independently, followed by meta-analysis and Grading of Recommendations Assessment, Development, and Evaluation assessment, if appropriate. EVIDENCE SYNTHESIS: This study included 27 articles with a total number of 25,593 participants, examining nutritional supplementation, prophylactic medication, and equipment modifications with mostly high or unclear risk of bias. Meta-analysis and Grading of Recommendations Assessment, Development, and Evaluation assessment could be performed for 3 comparisons: custom-made insoles versus no insoles, tropical/hot-weather boots versus leather boots, and shock-absorbing insoles versus nonshock-absorbing insoles interventions, all showing the very low quality of evidence. Some evidence was found to support the preventive effect of shock-absorbing insoles, basketball shoes, padded polyester socks, calcium with vitamin D supplementation, only calcium supplementation, protein supplementation, and dynamic patellofemoral braces. CONCLUSIONS: Although an evidence base for the efficacy of preventive interventions for musculoskeletal injuries in armed forces is weak, there are some indications for the preventive effect of shock-absorbing insoles, basketball shoes, padded polyester socks, supplementation of calcium alone or combined with vitamin D, protein supplementation, and dynamic patellofemoral braces on the incidence of musculoskeletal injuries.

Exercise Programs to Reduce the Risk of Musculoskeletal Injuries in Military Personnel: A Systematic Review and Meta-Analysis.

OBJECTIVE: To evaluate the effect of exercise programs on reduction of musculoskeletal injury (MSI) risk in military populations. DESIGN: Systematic review and meta-analysis. LITERATURE SURVEY: A database search was conducted in PubMed/MEDLINE, EMBASE, Cochrane Library, CINAHL, SPORTdiscus, WHO International Clinical Trials Registry Platform Search Portal, Open Gray, National Technical Reports Library, and reference lists of included articles up to July 2019. Randomized and cluster-randomized controlled trials evaluating exercise programs as preventive interventions for MSIs in armed forces compared to other exercise programs or to usual practice were eligible for inclusion. METHODOLOGY: Two authors independently assessed risk of bias and extracted data. Data were adjusted for clustering if necessary and pooled using the random-effects model when appropriate. SYNTHESIS: We included 15 trials in this review, with a total number of 14 370 participants. None of the included trials appeared to be free of any risk of bias. Meta-analysis and Grading of Recommendations, Assessment, Development and Evaluations (GRADE) assessment could be performed for static stretching compared to no stretching (3532 participants), showing low quality of evidence indicating no favorable effect of stretching. Gait retraining, an anterior knee-pain targeted program, and resistance exercises showed cautious favorable effects on reducing injury risk in military personnel. CONCLUSION: The current evidence base for exercise-based MSI prevention strategies in the military is of low quality. Areas worthy of further exploration include the effects of gait retraining, anterior knee-pain targeted programs, agility training, and resistance training programs, on medial tibial stress syndrome incidence, anterior knee pain incidence, attrition due to injuries and any type of MSI, respectively.

Epidemiology and Financial Burden of Musculoskeletal Injuries as the Leading Health Problem in the Military.

INTRODUCTION: Musculoskeletal injuries (MSIs) have direct impact on occupational readiness and task performance in military populations. Until this date, no epidemiologic data have been published concerning MSI incidence in the Netherlands Armed Forces (NAF). The aim of this study was to assess the MSI incidence and related costs in the NAF. METHODS: In this descriptive epidemiologic study, we collected injury surveillance data from the electronic patient records of multiple military units of the NAF. Using data of all new consultations with a military physician from January 1, 2014 to December 31, 2016, we calculated MSI incidence rates per 100 person-years, with a 95% confidence interval (CI). Physician care costs were determined based on the number of physician consults and the charge per appointment. We used two methods to determine productivity costs; the top-down microcosting method and the friction cost method. RESULTS: Our study sample included 22% (n = 8,847) of the total NAF population of 2016 (n =40,178). In this sample, consultations of MSIs accounted for 23.2% (n = 7,815) of all new consultations (n = 33,666). MSI incidence rates per unit ranged from 12.5 to53.3 per 100 person-years. In the total sample, MSI incidence rates were highest in the back (6.73, 95% CI 6.39-7.10), knee (5.04, 95% CI 4.74-5.35), and foot (4.79, 95% CI 4.50-5.10). The estimated costs for physician visits for MSIs in our sample were €0.69 million. Limited duty days accounted for €1.10 million productivity costs using top-down microcosting method. CONCLUSION: Our study provided evidence that MSIs result in substantial financial burden. Injuries of the back, knee, and foot account for the majority of demands on curative care for MSIs.