Evaluation of mortality among Marines, Navy personnel, and civilian workers exposed to contaminated drinking water at USMC base Camp Lejeune: a cohort study.

BACKGROUND: Drinking water at U.S. Marine Corps Base (MCB) Camp Lejeune, North Carolina was contaminated with trichloroethylene and other industrial solvents from 1953 to 1985. METHODS: A cohort mortality study was conducted of Marines/Navy personnel who, between 1975 and 1985, began service and were stationed at Camp Lejeune (N = 159,128) or MCB Camp Pendleton, California (N = 168,406), and civilian workers employed at Camp Lejeune (N = 7,332) or Camp Pendleton (N = 6,677) between October 1972 and December 1985. Camp Pendleton's drinking water was not contaminated with industrial solvents. Mortality follow-up was between 1979 and 2018. Proportional hazards regression was used to calculate adjusted hazard ratios (aHRs) comparing mortality rates between Camp Lejeune and Camp Pendleton cohorts. The ratio of upper and lower 95% confidence interval (CI) limits, or CIR, was used to evaluate the precision of aHRs. The study focused on underlying causes of death with aHRs ≥ 1.20 and CIRs ≤ 3. RESULTS: Deaths among Camp Lejeune and Camp Pendleton Marines/Navy personnel totaled 19,250 and 21,134, respectively. Deaths among Camp Lejeune and Camp Pendleton civilian workers totaled 3,055 and 3,280, respectively. Compared to Camp Pendleton Marines/Navy personnel, Camp Lejeune had aHRs ≥ 1.20 with CIRs ≤ 3 for cancers of the kidney (aHR = 1.21, 95% CI: 0.95, 1.54), esophagus (aHR = 1.24, 95% CI: 1.00, 1.54) and female breast (aHR = 1.20, 95% CI: 0.73, 1.98). Causes of death with aHRs ≥ 1.20 and CIR > 3, included Parkinson disease, myelodysplastic syndrome and cancers of the testes, cervix and ovary. Compared to Camp Pendleton civilian workers, Camp Lejeune had aHRs ≥ 1.20 with CIRs ≤ 3 for chronic kidney disease (aHR = 1.88, 95% CI: 1.13, 3.11) and Parkinson disease (aHR = 1.21, 95% CI: 0.72, 2.04). Female breast cancer had an aHR of 1.19 (95% CI: 0.76, 1.88), and aHRs ≥ 1.20 with CIRs > 3 were observed for kidney and pharyngeal cancers, melanoma, Hodgkin lymphoma, and chronic myeloid leukemia. Quantitative bias analyses indicated that confounding due to smoking and alcohol consumption would not appreciably impact the findings. CONCLUSION: Marines/Navy personnel and civilian workers likely exposed to contaminated drinking water at Camp Lejeune had increased hazard ratios for several causes of death compared to Camp Pendleton.

Sexually transmitted infections among active component members of the U.S. Armed Forces, 2015-2023.

This report summarizes incidence rates and trends of sexually transmitted infections (STIs) from 2015 through 2023 among active component service members of the U.S. Armed Forces. The data compiled for this report are derived from the medical surveillance of chlamydia, gonorrhea, and syphilis as nationally notifiable diseases. Case data for 2 additional STIs, human papilloma virus (HPV) and genital herpes simplex virus (HSV), are also presented. The crude total case rates of chlamydia and gonorrhea initially rose by an average of 6.7% and 9.8% per year, respectively, until 2019. From 2020 onwards, rates steadily declined. By 2023, chlamydia rates had dropped by approximately 39%, while gonorrhea rates had fallen by more than 40% for female, and 19% for male, service members. Initially syphilis increased, on average, 10% annually from 2015 to 2019, then declined in 2020, but resumed its upward trend through 2023, nearly doubling the 2015 rate in 2023. The total crude annual incidence rates of genital HPV and HSV exhibited downward trends in general over the surveillance period, decreasing by 30.7% and 24.7%, respectively. Age- and gender-adjusted case rates for chlamydia, gonorrhea, and syphilis remain elevated within the U.S. Armed Forces compared to the general U.S. population, which may be due to factors that include mandatory STI screening, more complete reporting, incomplete adjustment for age distribution, and inequitable comparisons between the military active duty and general U.S. populations. Social restrictions enacted during the COVID-19 pandemic may have contributed to declines in true case rates and screening coverage.

Internet-Guided Cognitive Behavioral Therapy for Insomnia Among Patients With Traumatic Brain Injury: A Randomized Clinical Trial.

Importance: Many military service members and veterans report insomnia after sustaining traumatic brain injury (TBI). Limitations of first-line treatment, cognitive-behavioral therapy for insomnia (CBT-I), include availability of qualified clinicians, low completion rates, and cost. Objective: To investigate the feasibility and efficacy of internet-guided CBT-I (eCBT-I) in military service members and veterans with insomnia and a history of TBI. Design, Setting, and Participants: This randomized clinical trial of fully remote internet-based interventions and evaluations was conducted from September 1, 2020, to June 30, 2021, with 3 months of follow-up. Participants included a volunteer sample of military service members and veterans aged 18 to 64 years with a history of mild TBI/concussion and at least moderately severe insomnia defined as an insomnia severity index (ISI) score of greater than 14 and Pittsburgh Sleep Quality Index of greater than 4. Self-reported race, ethnicity, and educational level were generally representative of the US military. Data were analyzed from October 21, 2021, to April 29, 2024. Intervention: Internet-based CBT-I delivered over 6 weekly lesson modules with assigned homework activities. Main Outcomes and Measures: The prespecified primary outcome measure was change in ISI score over time. Prespecified secondary outcome measures included self-reported measures of depression symptoms, posttraumatic stress disorder (PTSD) symptoms, sleep quality, migraine impact, and fatigue. Results: Of 204 people screened, 125 were randomized 3:1 to eCBT-I vs online sleep education, and 106 completed baseline evaluations (83 men [78.3%]; mean [SD] age, 42 [12] years). Of these, 22 participants (20.8%) were Hispanic or Latino and 78 (73.6%) were White. Fifty participants completed postintervention evaluations, and 41 completed the 3-month follow-up. Baseline mean (SD) ISI scores were 19.7 (4.0) in those randomized to eCBT-I and 18.9 (5.0) in those randomized to sleep education. After intervention, mean (SD) ISI scores were 13.7 (5.6) in those randomized to eCBT-I and 16.6 (5.7) in those randomized to sleep education. The difference in the extent of reduction in ISI scores between groups was 3.5 (95% CI,-6.5 to -0.4 [P = .03]; Cohen d, -0.32 [95% CI, -0.70 to -0.04]). In the eCBT-I group, the extent of insomnia improvement correlated with the extent of depressive symptom improvement (Spearman ρ = 0.68 [P < .001]), PTSD symptoms (ρ = 0.36 [P = .04]), sleep quality (ρ = 0.54 [P = .001]), and fatigue impact (ρ = -0.58 [P < .001]) but not migraine-related disability. Conclusions and Relevance: The findings of this randomized clinical trial suggest that fully remote eCBT-I was moderately feasible and effective for self-reported insomnia and depression symptoms in military service members and veterans with a history of TBI. There is great potential benefit for eCBT-I due to low availability and cost of qualified CBT-I clinicians, although optimization of completion rates remains a challenge. Future studies may use home-based objective sleep assessments and should increase study retention. Trial Registration: ClinicalTrials.gov Identifier: NCT04377009.

Prevalence of smoking among national military service recruits in UAE.

Background: According to the various screening programs conducted, the prevalence of tobacco use among UAE Nationals is high. A considerable increase is also seen in various forms of smoking is seen among young military men during deployment which results in loss of physical health, less productivity, readiness and increased health care utilization. Also smokers are more likely to develop other addictions and chronic medical conditions. Aim: To estimate the prevalence of smoking among national military service recruits in the United Arab Emirates and to find its relation with various factors: socio-demographics, lifestyle, comorbidities, and military environment. Methods: A cross sectional study was conducted amongst national service recruits selected by random stratification through a self-administered anonymized questionnaire which was distributed to a final sample of 369 patients. Data was analyzed using SPSS version 16. Chi square, percentage and frequencies were used to present the data where applicable. A p < 0.05 was considered to be significant. Results: The prevalence of smoking among national military service recruits was 41.6%. As the level of education increased the prevalence of smoking decreased. Smokers with insufficient income, divorced or widowed recruits tend to smoke more as against single and married recruits. Smoking rates were decreased in those who exercise regularly. There was a significant relationship between smoking status and chronic diseases. Smoker gatherings inside military campus encouraged initiation of smoking or its continuity. About half of the smokers were not satisfied with environment at military facilities. Conclusion: Smoking has high prevalence among national service military recruits. For this reason, a goal directed future plan toward screening of smokers among recruits and assigning them to smoking cessation clinics and educational seminars prior to joining the national service is the need of the hour.

Spinal Cord Stimulator Inequities Within the US Military Health System.

OBJECTIVES: Although studies have described inequities in spinal cord stimulation (SCS) receipt, there is a lack of information to inform system-level changes to support health care equity. This study evaluated whether Black patients exhaust more treatment options than do White patients, before receiving SCS. MATERIALS AND METHODS: This retrospective cohort study included claims data of Black and non-Latinx White patients who were active-duty service members or military retirees who received a persistent spinal pain syndrome (PSPS) diagnosis associated with back surgery within the US Military Health System, January 2017 to January 2020 (N = 8753). A generalized linear model examined predictors of SCS receipt within two years of diagnosis, including the interaction between race and number of pain-treatment types received. RESULTS: In the generalized linear model, Black patients (10.3% [8.7%, 12.0%]) were less likely to receive SCS than were White patients (13.6% [12.7%, 14.6%]) The interaction term was significant; White patients who received zero to three different types of treatments were more likely to receive SCS than were Black patients who received zero to three treatments, whereas Black and White patients who received >three treatments had similar likelihoods of receiving a SCS. CONCLUSIONS: In a health care system with intended universal access, White patients diagnosed with PSPS tried fewer treatment types before receiving SCS, whereas the number of treatment types tried was not significantly related to SCS receipt in Black patients. Overall, Black patients received SCS less often than did White patients. Findings indicate the need for structured referral pathways, provider evaluation on equity metrics, and top-down support.

Linked Exposures Across Databases: an exposure common data elements aggregation framework to facilitate clinical exposure review.

Understanding the health outcomes of military exposures is of critical importance for Veterans, their health care team, and national leaders. Approximately 43% of Veterans report military exposure concerns to their VA providers. Understanding the causal influences of environmental exposures on health is a complex exposure science task and often requires interpreting multiple data sources; particularly when exposure pathways and multi-exposure interactions are ill-defined, as is the case for complex and emerging military service exposures. Thus, there is a need to standardize clinically meaningful exposure metrics from different data sources to guide clinicians and researchers with a consistent model for investigating and communicating exposure risk profiles. The Linked Exposures Across Databases (LEAD) framework provides a unifying model for characterizing exposures from different exposure databases with a focus on providing clinically relevant exposure metrics. Application of LEAD is demonstrated through comparison of different military exposure data sources: Veteran Military Occupational and Environmental Exposure Assessment Tool (VMOAT), Individual Longitudinal Exposure Record (ILER) database, and a military incident report database, the Explosive Ordnance Disposal Information Management System (EODIMS). This cohesive method for evaluating military exposures leverages established information with new sources of data and has the potential to influence how military exposure data is integrated into exposure health care and investigational models.

Development of Chronic Pain Conditions Among Women in the Military Health System.

Importance: The incidence of chronic pain has been increasing over the last decades and may be associated with the stress of deployment in active-duty servicewomen (ADSW) as well as women civilian dependents whose spouse or partner served on active duty. Objective: To assess incidence of chronic pain among active-duty servicewomen and women civilian dependents with service during 2006 to 2013 compared with incidence among like individuals at a time of reduced combat exposure and deployment intensity (2014-2020). Design, Setting, and Participants: This cohort study used claims data from the Military Health System data repository to identify ADSW and dependents who were diagnosed with chronic pain. The incidence of chronic pain among individuals associated with service during 2006 to 2013 was compared with 2014 to 2020 incidence. Data were analyzed from September 2023 to April 2024. Main Outcomes and Measures: The primary outcome was the diagnosis of chronic pain. Multivariable logistic regression analyses were used to adjust for confounding, and secondary analyses were performed to account for interactions between time period and proxies for socioeconomic status and combat exposure. Results: A total of 3 473 401 individuals (median [IQR] age, 29.0 [22.0-46.0] years) were included, with 644 478 ADSW (18.6%). Compared with ADSW in 2014 to 2020, ADSW in 2006 to 2013 had significantly increased odds of chronic pain (odds ratio [OR], 1.53; 95% CI, 1.48-1.58). The odds of chronic pain among dependents in 2006 to 2013 was also significantly higher compared with dependents from 2014 to 2020 (OR, 1.96; 95% CI, 1.93-1.99). The proxy for socioeconomic status was significantly associated with an increased odds of chronic pain (2006-2013 junior enlisted ADSWs: OR, 1.95; 95% CI, 1.83-2.09; 2006-2013 junior enlisted dependents: OR, 3.05; 95% CI, 2.87-3.25). Conclusions and Relevance: This cohort study found significant increases in the diagnosis of chronic pain among ADSW and civilian dependents affiliated with the military during a period of heightened deployment intensity (2006-2013). The effects of disparate support structures, coping strategies, stress regulation, and exposure to military sexual trauma may apply to both women veterans and civilian dependents.

Prevalence of burnout among military personnel in the plateau region of China: a cross-sectional survey.

OBJECTIVES: The geographical environment and military activities in the plateau area pose potential work-related stressors for military personnel, leading to burnout which is an external manifestation of internal energy exhaustion caused by stress. Without countermeasures, this can result in serious military problems. This study aims to examine the association between burnout and occupational stressors among military personnel stationed in the plateau area of China. MATERIAL AND METHODS: A stratified randomized cluster sampling survey was conducted among 2026 military personnel from 6 different troops stationed in the plateau area of China. The Chinese Maslach Burnout Inventory-General Survey(MBI-GS in Chinese) was administered from March 2022 to December 2023, and data were analyzed using SPSS version 25. RESULTS: A total of 2026 military personnel participated in the survey. The mean overall burnout score was 3.37 ± 0.73, with emotional exhaustion at 2.69 ± 0.89, depersonalization at 3.58 ± 0.92, and professional achievement at 3.81 ± 0.85 levels respectively reported by participants on average scale scores ranging from zero to six. Severe level of burnout was reported by 43.2% of participants while medium level of burnout was reported by 54 .3%. Age, education level, length of military service, and household income were identified as important factors influencing burnout. CONCLUSION: This study highlights a relatively high prevalence of burnout among military personnel stationed in plateau areas necessitating attention towards their occupational health particularly focusing on working hours and economic aspects so as to formulate effective policies and implement intervention measures that strengthen career development for soldiers deployed in such regions.

Surveillance outcomes of respiratory pathogen infections during the 2021-2022 season among U.S. Military Health System beneficiaries, October 3, 2021-October 1, 2022.

The Department of Defense Global Respiratory Pathogen Surveillance Program conducts continuous surveillance for influenza, severe acute respiratory syndrome 2 (SARS-CoV-2), and other respiratory pathogens at 104 sentinel sites across the globe. These sites submitted 65,475 respiratory specimens for clinical diagnostic testing during the 2021-2022 surveillance season. The predominant influenza strain was influenza A(H3N2) (n=777), of which 99.9% of strains were in clade 3C.2a1b.2a2. A total of 21,466 SARSCoV-2-positive specimens were identified, and 12,225 of the associated viruses were successfully sequenced. The Delta variant predominated at the start of the season, until December 2021, when Omicron became dominant. Most circulating SARS-CoV-2 viruses were subsequently held by Omicron sublineages BA.1, BA.2, and BA.5 during the season. Clinical manifestation, obtained through a self-reported questionnaire, found that cough, sinus congestion, and runny nose complaints were the most common symptoms presenting among all pathogens. Sentinel surveillance can provide useful epidemiological data to supplement other disease monitoring activities, and has become increasingly useful with increasing numbers of individuals utilizing COVID-19 rapid self-test kits and reductions in outpatient visits for routine respiratory testing.

The nature and impacts of deployment-related encounters with children among Canadian military Veterans: a qualitative analysis.

Background: As armed conflict grows increasingly complex, the involvement of children in armed violence across diverse roles is rising. Consequently, military personnel are more likely to encounter children during deployment. However, little is known about deployment-related encounters with children and their impact on the mental health of military personnel and Veterans.Objective: This study qualitatively examines the nature and impacts of deployment-related encounters with children.Methods: We conducted semi-structured interviews with 16 Canadian Armed Forces Veterans, eliciting rich information on the nature of child encounters on deployment, the psycho-social-spiritual impacts of these encounters, and perceptions of support. Interview transcripts were analysed using thematic analysis.Results: Six primary themes were identified: types of encounters (i.e. factual aspects of deployment-related encounters with children), contextual factors (i.e. aspects of the mission, environment, and personal context relevant to one's experience of the encounter), appraisals of encounters (i.e. sensory or sense-making experiences relevant to the encounter), impacts of encounters (i.e. psycho-social, existential, and occupational impacts), coping strategies engaged in both during and after deployment, and support experiences, describing both formal and informal sources of support.Conclusions: Encounters with children are diverse and highly stressful, resulting in impacts pertinent to mental health, including psychological and moral distress, and difficulties with identity, spirituality, and relationships. These impacts are prompted by complex interactions among appraisals, expectations of morality, cultural norms, and professional duties and are amplified by various personal factors (e.g. childhood maltreatment history, parenthood), feelings of unpreparedness, and lack of post-deployment support. Implications for prevention, intervention, and policy are discussed with the aim of informing future efforts to safeguard and support military personnel facing a high likelihood of encounters with children.

Deployment-related encounters with children result in diverse impacts, including psychological and moral distress, along with disruptions in identity, spirituality, and interpersonal relationships.Encounters with children during military deployments are diverse and highly stressful, characterized by complex interactions among appraisals and expectations of morality, cultural norms, and professional duties.Emphasis on feeling unprepared for encounters with children highlights the need for future efforts to safeguard and support military personnel facing such situations.

Service Dogs for Veterans and Military Members With Posttraumatic Stress Disorder: A Nonrandomized Controlled Trial.

Importance: Military members and veterans (hereafter, veterans) with posttraumatic stress disorder (PTSD) increasingly seek psychiatric service dogs as a complementary intervention, yet the effectiveness of service dogs is understudied. Objective: To estimate the associations between psychiatric service dog partnership and self-reported and clinician-rated PTSD symptom severity, depression, anxiety, and psychosocial functioning after 3 months of intervention among veterans. Design, Setting, and Participants: This nonrandomized controlled trial used standardized and validated assessment instruments completed by participants and administered by blinded clinicians. Recruitment, eligibility screening, and enrollment were conducted between August 2017 and December 2019. Veterans were recruited using the database of an accredited nonprofit service dog organization with constituents throughout the US. Participants were veterans with a PTSD diagnosis; they were allocated to either the intervention group (n = 81) or control group (n = 75). Outcome assessments were performed at baseline and at the 3-month follow-up. Data analyses were completed in October 2023. Interventions: Participants allocated to the intervention group received a psychiatric service dog for PTSD, whereas those allocated to the control group remained on the waiting list based on the date of application submitted to the service dog organization. Both groups had unrestricted access to usual care. Main Outcomes and Measures: The primary outcomes were PTSD symptom severity, depression, and anxiety after 3 months, and the secondary outcomes were psychosocial functioning, such as quality of life and social health. The self-reported PTSD Checklist for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) was used to measure symptom severity, and the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) was used to assess PTSD diagnosis (score range for both instruments: 0-80, with higher scores indicating greater PTSD symptoms). Results: The 156 participants included in the trial had a mean (SD) age of 37.6 (8.3) years and included 117 males (75%), 17 Black or African American individuals (11%), 30 Hispanic individuals (19%), and 117 White individuals (76%). Compared with the control group, the intervention group had significantly lower PTSD symptom severity based on the PTSD Checklist for DSM-5 mean (SD) score (41.9 [16.9] vs 51.7 [16.1]; difference in means, -11.5 [95% CI, -16.2 to -6.6]; P < .001) and the CAPS-5 mean (SD) score (30.2 [10.2] vs 36.9 [10.2]; difference in means, -7.0 [95% CI, -10.8 to -4.5]; P < .001) at 3 months. The intervention group also had significantly lower depression scores (odds ratio [OR], 0.45 [95% CI, 0.23-0.86]; difference in means, -3.3 [95% CI, -6.8 to -0.6]), anxiety (OR, 0.25 [95% CI, 0.13-0.50]; difference in means, -4.4 [95% CI, -6.9 to -2.1]), and most areas of psychosocial functioning (eg, social isolation: OR, 0.34 [95% CI, 0.18-0.64]). Conclusions and Relevance: This nonrandomized controlled trial found that compared with usual care alone, partnership with a trained psychiatric service dog was associated with lower PTSD symptom severity and higher psychosocial functioning in veterans. Psychiatric service dogs may be an effective complementary intervention for military service-related PTSD. Trial Registration: ClinicalTrials.gov ID: NCT03245814.

Foreword: U.S. Marine Gender Integration in Recruit Training.

The 2020 National Defense Authorization Act mandated that the Marine Corps not segregate recruit training by gender. This Military Medicine supplement details an independent academic study contracted by the Marine Corps Training and Education Command to inform the Marine Corps' future approaches to gender integration at recruit training. The authors conclude that with proper science-based training and an intentional approach to gender integration, the Marine Corps can bolster gender integration without losing its traditions, high standards, or warrior ethos in recruit training. A feasible path lies ahead to enhance the Corps' legacy of success. This special issue supports the Marine Corps Training and Education Command 2030 posture statement for leveraging science and technology for policy and doctrine to prepare and modernize the Marine Corps for the future operating environment.

Recruit Profiles Across the U.S. Armed Forces: Implications for Increasing Gender Integration in Recruit Training.

INTRODUCTION: This article uses recent survey data from a study on gender integration at recruit training across the U.S. Armed Forces to examine service, gender, and training differences in recruit's gender attitudes, beliefs, and cohesion metrics. In addition to providing a descriptive understanding of our recruit sample, this article examines factors germane to gender integration at recruit training such as gender attitudes, sexist beliefs, and unit cohesion. MATERIALS AND METHODS: This article uses data from a survey of U.S. Marine Corps (USMC), U.S. Army, U.S. Air Force, U.S. Navy, and U.S. Coast Guard recruits as part of a USMC-commissioned study to develop alternate models and recommendations for increasing gender integration in USMC recruit training. At all sites but the USMC, recruits completed the survey 1 to 2 weeks before graduation. At the Marine Corps Recruit Depots, recruits participated in the survey at the beginning (week 2) and end (week 11) of their 13-week training cycle. A 19-question survey captured sociodemographic information, perspectives and experiences during recruit training, and gender attitudes and beliefs. Analyses were conducted on the sample with complete data on the measures reported, including those USMC recruits observed at both week 2 and week 11 (n = 629). Descriptive statistics (percentage) were calculated for all categorical outcome variables. Outcome variables (cohesion, gender, and sexism attitudes) were compared between groups using chi-squared tests or Fisher's exact tests, as appropriate. RESULTS: Recruits differed significantly across services in perceptions of unit cohesion on 3 of the 4 indicators: Platoon members are cooperative, know they can depend on each other, and really respect each other (P < .05). These differences appear to be driven by female recruit difference across service. They reported significant differences in gender role attitudes across the services, with USMC recruits being most likely to endorse traditional gender roles compared to other service recruits. Male USMC recruits were significantly more likely than their female peers to agree that men should achieve outside the home and women should take care of the home and family (21.3% versus 6.3%, P < .05). The only statistical differences in attitudes about equality of treatment and opportunity among recruits were between male and female USMC recruits. All items capturing sexist attitudes elicited statistically significant differences between male USMC recruits and male recruits in other services (P < .05). There were significant differences in all sexism measures between male and female USMC recruits (P < .05). There is a significant decline in some sexist attitudes between weeks 2 and 11 of training among male USMC recruits (P < .05). Nearly one-half to three-fourths of male USMC recruits hold sexist attitudes, even near the end of recruit training. CONCLUSIONS: The disparate gender and sexism attitudes of male USMC recruits compared with their peers in other services, and their fellow female USMC recruits suggest efforts to increase gender integration at entry-level training are needed, but also may be challenging since male USMC recruits report the highest levels of sexist attitudes among all recruits.

Unsupervised Machine Learning in Countermovement Jump and Isometric Mid-Thigh Pull Performance Produces Distinct Combat and Physical Fitness Clusters in Male and Female U.S. Marine Corps Recruits.

INTRODUCTION: Several challenges face the U.S. Marine Corps (USMC) and other services in their efforts to design recruit training to augment warfighter mobility and resilience in both male and female recruits as part of an integrated model. Strength and power underpin many of the physical competencies required to meet the occupational demands one might face in military. As the military considers adopting force plate technology to assess indices of strength and power, an opportunity presents itself for the use of machine learning on large datasets to deduce the relevance of variables related to performance and injury risk. The primary aim of this study was to determine whether cluster analysis on baseline strength and power data derived from countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) adequately partitions men and women entering recruit training into distinct performance clusters. The secondary aim of this study is then to assess the between-cluster frequencies of musculoskeletal injury (MSKI). MATERIALS AND METHODS: Five hundred and sixty-five males (n = 386) and females (n = 179) at the Marine Corps Recruit Depots located at Parris Island and San Diego were enrolled in the study. Recruits performed CMJ and IMTP tests at the onset of training. Injury data were collected via medical chart review. Combat fitness test (CFT) and physical fitness test (PFT) results were provided to the study team by the USMC. A k-means cluster analysis was performed on CMJ relative peak power, IMTP relative peak force, and dynamic strength index. Independent sample t-tests and Cohen's d effect sizes assessed between-cluster differences in CFT and PFT performance. Differences in cumulative incidence of lower extremity %MSKIs were analyzed using Fisher's exact test. Relative risk and 95% confidence intervals (CIs) were also calculated. RESULTS: The overall effects of cluster designation on CMJ and IMTP outcomes ranged from moderate (relative peak power: d = -0.68, 95% CI, -0.85 to -0.51) to large (relative peak force: d = -1.69, 95% CI, -1.88 to -1.49; dynamic strength index: d = 1.20, 95% CI, 1.02-1.38), indicating acceptable k-means cluster partitioning. Independent sample t-tests revealed that both men and women in cluster 2 (C2) significantly outperformed those in cluster 1 (C1) in all events of the CFT and PFT (P < .05). The overall and within-gender effect of cluster designation on both CFT and PFT performance ranged from small (d > 0.2) to moderate (d > 0.5). Men in C2, the high-performing cluster, demonstrated a significantly lower incidence of ankle MSKI (P = .04, RR = 0.2, 95% CI, 0.1-1.0). No other between-cluster differences in MSKI were statistically significant. CONCLUSIONS: Our results indicate that strength and power metrics derived from force plate tests effectively partition USMC male and female recruits into distinct performance clusters with relevance to tactical and physical fitness using k-means clustering. These data support the potential for expanded use of force plates in assessing readiness in a cohort of men and women entering USMC recruit training. The ability to pre-emptively identify high and low performers in the CFT and PFT can aid in leadership developing frameworks for tailoring training to enhance combat and physical fitness with benchmark values of strength and power.

A Sex Comparison of the Physical and Physiological Demands of United States Marine Corps Recruit Training.

INTRODUCTION: The U.S. Marine Corps (USMC) recruit training is a 13-week preparatory period for military service men and women. Differences in absolute performance capabilities between sexes may impact physical and physiological responses to the demands of recruit training. The purpose of this study was to monitor U.S. Marine Corps recruits throughout recruit training to comparatively assess workload, sleep, stress, and performance responses in men and women. MATERIALS AND METHODS: A total of 281 recruits (men = 182 and women = 99; age = 19 ± 2 years) were monitored and tested. Workload, sleep, and stress assessments occurred at week 2, week 7/8, and week 11 of training. Workload (energy expenditure per kg body mass [EEREL], distance [DIS], steps) and sleep (continuity and duration) were tracked over 72-hour periods using wearable accelerometry and heart rate technology. Stress responses were determined through salivary cortisol analyses. Performance testing, consisting of countermovement vertical jump (CMJ) and isometric mid-thigh pull (IMTP) performance relative to body mass, occurred at weeks 2 and 11. Linear mixed models were used to test for sex, time, and sex-by-time interactions (α < .05). RESULTS: On average, recruits covered 13.0 ± 2.7 km/day, expended 3,762 ± 765 calories/day, and slept 6.2 ± 1.1 hours/night. Sex-by-time interactions were found for DIS, steps, sleep duration, cortisol, and CMJREL performance (P < .05). Planned contrasts revealed that men covered more DIS than women at week 7/8 (P < .001). Women experienced greater step counts compared to men at week 11 (P = .004). Women experienced no significant change in sleep duration (P > .05), whereas men increased sleep duration from week 2 to week 7/8 (P = .03). Women experienced greater sleep duration at week 2 (P = .03) and week 11 (P = .02) compared to men. Women exhibited higher cortisol levels than men at week 2 (P < .001) and week 11 (P < .001). Women experienced declines in cortisol at week 7 compared to week 2 (P < .001). Men experienced no changes in cortisol response at any timepoint (P > .05). Both sexes experienced declines in CMJREL from week 2 to week 11 (P > .001). Sex main effects were observed for EEREL, DIS, CMJREL, and IMTPREL (P < .05) with men experiencing greater overall workloads and producing greater strength and power metrics. Sex main effects were also found for sleep continuity and cortisol (P < .05), for which men experienced lower values compared to women. Time main effects were observed for EEREL, DIS, steps, cortisol, CMJREL, and IMTPREL (P < .05). CONCLUSIONS: This study not only highlights the known sex differences between men and women but also sheds light on the different physical and physiological responses of each sex to military training. Interestingly, the greatest physical demands incurred earlier in the training cycle. Despite declining workloads, the stress response was maintained throughout the training, which may have implications for adaptation and performance. In addition, average sleep duration fell notably below recommendations for optimizing health and recovery. Effectively monitoring the demands and performance outcomes during recruit training is essential for determining individual fitness capabilities, as well as establishing the effectiveness of a training program. Individual performance assessments and adequately periodized workloads may help to optimize recruit training for both men and women.

Recruit Perspectives on Gender Integration at Recruit Training: A Comparison by Service and Gender.

INTRODUCTION: Recruit training is the initial entry for enlisted personnel in the military. The Services execute gender-integrated recruit training differently. The U.S. Marine Corps (USMC) maintains same-gender platoons led by same-gender drill instructors in integrated companies; further integration occurs at select training events. The other Services train recruits in gender-integrated units with mixed-gender drill instructor teams. We examine recruits' experiences and perceptions of gender integration at recruit training, their desired level of integration, and preferences for increasing gender integration, comparing by Service and gender. MATERIALS AND METHODS: Recruit perspectives and experiences were captured in a 19-question survey (n = 632) and 90-min focus groups (n = 260) near graduation from recruit training. Data were collected from June to November 2021. Because of the Coronavirus disease (COVID-19) pandemic restrictions, the Navy and Air Force were not conducting gender-integrated recruit training during data collection. Outcome variables were compared cross-Service by gender and within Service by gender using chi-squared tests or Fisher's exact tests, as appropriate; focus group data were analyzed using initial and secondary coding schemes. Three USMC training models, varied by level of integration, were also analyzed (Male-Only, Series Track, and Integrated Company). RESULTS: Significant gender differences across and within Service emerged in recruits' experience being trained by an opposite-gender instructor. Male recruits had significant differences by Service (P < .001), and USMC female recruits reported being trained by male instructors more than their male peers by female instructors (Series Track P = .002; Integrated Company P < .001). In the focus groups, recruits described common differences with how men and women embodied being a drill instructor. Significant gender differences across (both male and female P < .001) and within Service were reported for closeness of training with opposite-gender peers (Air Force P = .028; U.S. Marine Corps (USMC) Integrated Company P = .010; Army P = .048), an expected finding given varied integration during data collection. Male and female recruits had significant differences by Service in their preference for integration at the lowest unit level (both male and female P < .001), with those who experienced integrated training showing higher levels of endorsement. In the focus groups, recruits articulated benefits and challenges of gender-integrated recruit training. Significant gender differences across Service emerged in preferences for more integration in specific training activities. Within Service, female USMC Integrated Company recruits wanted more integration in tactical/field, physical fitness, and classroom training than their male peers (P < .001 for all). In the focus groups, USMC recruits of both genders desired more integrated training events, particularly those involving combat and tactical skill development. CONCLUSIONS: This study provided an opportunity to examine recruit perspectives on gender-integrated training. Services valuing opposite-gender instructor exposure in recruit training must ensure that male recruits are being taught and led by female instructors given disproportionate demographics. Recruits who experienced integrated training were more supportive of integration, indicating that this experience may increase their support for gender-integrated training units and environments. Today's recruits understand that they are entering gender-integrated working environments, and our results indicate that they expect recruit training to mirror that reality.