United States Marine Corps Recruit Training Demands Associated With Performance Outcomes

INTRODUCTION

United States Marine Corps' (USMC) recruit training is a 13-week program designed to maximize physical and mental performance adaptations. The purpose of this study was to evaluate the training demands and characteristics that are associated with performance outcomes during USMC recruit training.

MATERIALS AND METHODS

A total of 196 recruits (M = 97 and W = 99) were monitored and tested throughout training. Laboratory-based performance testing occurred at the start of weeks 2 and 11 and consisted of body mass assessments, countermovement vertical jump, and isometric mid-thigh pull. Military-specific performance testing occurred twice within the first 8 weeks of training and included the physical fitness test (PFT) and combat fitness test (CFT) implemented by the USMC. Resilience data were collected at week 2 using the Connor-Davidson Resilience Scale. Workload, sleep, and stress responses were monitored at weeks 2, 7, and 11. Recruits were provided with a wearable tracking device which utilized heart rate and accelerometry-based technology to determine energy expenditure (EE), distances (DIS), and sleep metrics. Data were averaged over a 3-day period. Salivary cortisol testing occurred at the start of each monitoring week. Change scores were calculated for performance tests, and body mass was calculated from data obtained at week 2 to week 11. Area under the curve was calculated for the workload, sleep metrics, and cortisol responses using the trapezoidal method. Pearson product-moment correlations (r) were used to assess the relationships between training demands and performance. An α level of 0.05 was used to establish significance.

RESULTS

A moderate positive correlation was found between changes in body mass and peak power (P < .001; r = 0.43). Weak positive correlations were found between changes in body mass and peak force (P = .002; r = 0.28), as well as body mass and resilience (P = .03; r = 0.19). A moderate negative correlation was observed between changes in body mass and PFT (P < .001; r = -0.49). A weak negative correlation was found between changes in body mass and EE (P = .003; r = -0.24). A weak negative correlation was found between changes in peak power and EE (P = .001; r = -0.29). A weak positive correlation was found between changes in peak power and changes in CFT (P = .05; r = 0.19) A weak negative correlation was found between changes in sleep continuity and CFT (P = .02; r = -0.20). A weak negative correlation was found between cortisol and changes in PFT (P = .05; r = -0.20). A weak negative correlation was found between cortisol and both EE (P = .001; r = -0.27) and DIS (P = .045; r = -0.16). A weak negative correlation was found between EE and sleep continuity (P < .001; r = -0.34). Weak negative correlations were found between sleep duration and both DIS (P = .01; r = -0.18) and steps (P = .003; r = -0.21).

CONCLUSIONS

Increases in body mass throughout training were positively associated with strength and power changes, but negatively related to PFT scores. Changes in peak power related to improvements in CFT scores; however, higher workloads (i.e., EE) were negatively associated with peak power. The identification of the USMC physical and physiological training demands that are associated with performance outcomes may be a valuable resource to guide conditioning efforts to boost military readiness.

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.

Design Considerations for a Multidisciplinary Approach to Provide Policy Recommendations on Gender-Integrated Recruit Training in the Marine Corps

INTRODUCTION

Recruit training is designed to transform civilians into physically fit military service members, who embody their service's core values and possess military discipline and skills. At the time this research began, the U.S. Marine Corps (USMC) remained the only service that segregated recruits by gender at the lowest unit level (e.g., platoon) and employed gender-segregated drill instructor teams. USMC's Marine Corps Recruit Depots (MCRD) must comply with a 2020 Congressional Mandate to not segregate training by gender in Parris Island by 2025 and San Diego by 2028. In turn, USMC requested an independent scientific study to analyze current approaches to gender integration at recruit training to propose alternate models and other policy recommendations that increase gender integration while maintaining current USMC standards. The Marine Corps is currently evaluating alternate models and recommendations to optimize entry-level training. This article outlines considerations for choosing the optimal research study design, research methods, and types of data collected in a study intended to provide policy recommendations on gender-integrated recruit training for the USMC.

MATERIALS AND METHODS

Research data were collected during visits to the MCRDs and selected recruit training locations for the Army, Air Force, Navy, and Coast Guard. Data collection on USMC recruits from three cohorts involved social science assessments (focus groups and surveys) and human performance testing (countermovement jumps and isometric mid-thigh pulls, sleep and activity wearables, and cortisol data) at multiple points in the training cycle. Data on recruits from the sister services were limited to social science assessments. Approximately 600 recruits between the two MCRDs and 160 recruits from the sister services participated in the study during a 7-month timeframe in 2021. The research team conducted extensive ethnographic observations of recruit training at all selected research sites and interviewed training cadre, drill instructors, and service leadership responsible for recruit training (∼90 interviews). Additionally, the research team interviewed 20 experts on gender integration or recruit training who possessed alternate viewpoints from the current USMC practice.

RESULTS

The mixed methods study was designed to assess the current gender integration practices at recruit training across the services to generate alternative models of gender integration for USMC. The research team developed a set of multidisciplinary objectives and research questions serving as the foundation of the research study design and data collection process. The study was designed to collect qualitative, quantitative, and administrative data informed by social science and human performance disciplines. To ensure that all aspects and implications relevant to gender integration were considered, select data were collected across services and with stakeholders at all levels.

CONCLUSIONS

This multidisciplinary research approach provided a comprehensive picture of the current USMC recruit training models. The research team captured multiple perspectives and data points for analysis through an expansive view on gender integration across all services, by interacting with participants at all levels of the institutions in varied ways. The information and data gathered enabled the research team to establish objective, data-driven alternate models, and recommendations for enhancing gender integration at recruit training for the USMC.

Outcome metrics utilized in evaluations of programs and interventions for combat and operational stress: A review of psychometric properties

The Department of Defense has mandated combat and operational stress control (COSC) efforts for the Services since 1999. Although several COSC-related programs have been implemented, few have undergone evaluation, and no standardized metrics have been established to assess their effectiveness and utility. The purpose of this review was to characterize the content and psychometrics of measures that have been utilized as outcome metrics in evaluations of COSC-related programs and interventions. Systematic literature searches were conducted for publications that: a) evaluated at least one measure from U.S. service members who participated in a program or intervention to prevent or reduce the adverse effects of combat and operational stress; and b) reported U.S. data on the internal consistency, test-retest reliability, convergent validity, and sensitivity/specificity of the identified measures. This process identified 15 measures for which psychometric properties were reviewed for acceptability based on recommended criteria. Identified measures varied from well-validated measures to newer instruments for which more data is needed on one or more of the target psychometric properties. Aside from internal consistency, psychometric data from U.S. military samples were sparse. Results further suggested that some measures might have reduced sensitivity in service members under certain conditions, such as large-scale screening. Additional studies are needed to validate COSC-relevant measures in service members. Future evaluations of programs and interventions for combat and operational stress should select measures that will increase the consistency of the literature, allow comparisons across studies, and ensure alignment with the objectives of identified programs.

Psychophysiology, Cognitive Function, and Musculoskeletal Status Holistically Explain Tactical Performance Readiness and Resilience

ABSTRACT

Thompson, AG, Ramadan, JH, Alexander, JS, and Galster, SM. Psychophysiology, cognitive function, and musculoskeletal status holistically explain tactical performance readiness and resilience. J Strength Cond Res 37(12): 2443-2456, 2023-This study aimed to advance the techniques used in quantifying holistic readiness and resilience within military personnel. Tactical performers, instructors, and applied human performance scientists designed a weeklong competition to reflect realistic operational demands, test specific underlying performance constructs, and elucidate how modernized assessments could drive programmatic action. By placing first in their installation's local preliminary competition, 34 active-duty Marines earned the opportunity to compete in a series of 7 intense events for the title of champion. All inferential statistics were set to a p ≤ 0.05 level of significance. Morning heart rate variability identified top from bottom quartile finishers before a single competition event. By day 3, morning countermovement jump force production (normalized reactive strength index-modified) and cognitive psychomotor vigilance were significant indicators of performance resilience and final competition group rank. Heart rate variability also tracked performer readiness across time, identifying within-group and between-group differences among top, bottom, and field. Collectively, these holistic assessments proved significant markers of acute and chronic tactical performance capabilities. In summary, the incorporation of psychophysiological monitoring, cognitive performance testing, and musculoskeletal force plate evaluations could help inform selection and support needs, drive workload or recovery modulation, and provide critical metrics for evaluating training efficacy and operational readiness. Defense organizations should consider routinely incorporating and actioning similar holistic status monitoring strategies in training and operational settings. Moreover, leveraging other tactical competitions may provide key opportunities for advancing the standard of practice through additional scientific investigation.

Performance changes during repeated military occupational test and its associations to physical performance

The present study investigated performance changes during three runs (1 min recovery) of repeated military simulation task test (RMST) and its associations with physical performance. Voluntary male soldiers (N = 114) participated in a series of measurements of physical performance. Lower body explosive force production, anaerobic endurance and upper body strength endurance together explained 58% of the variance in the first RSMT (p < 0.001). The same variables explained the variance in the second and third runs of RSMT by 60% and 51%, but explosive force production was replaced with aerobic endurance, assessed by the 3.2 km loaded run (p < 0.001). This study demonstrated that the role of explosive power of the lower body decreased and military specific aerobic endurance increased when occupational performance was assessed under acute fatigue even during a short high-intensity test. These results may benefit tactical strength and conditioning coaches in training optimisation for improved occupational performance in military.Practioners summary: Soldiers are required to perform occupational tasks in a repeated manner with short recovery time. In the present study, the role of explosive power of the lower body decreased and military specific aerobic endurance increased when occupational performance was assessed with a repeated high-intensity task specific performance test.

Leading indicators of readiness among the general Army and Special Operations Forces: Predictive and psychometric analysis of the Global Assessment Tool

Self-assessments are commonly used to track Army readiness in specialized communities, but they are rarely analyzed for reliability and predictive validity. Before introducing new assessments, existing ones should be reevaluated. We examined the Global Assessment Tool (GAT), an annual Army-required self-assessment with multiple psychosocial and health behavior short scales. Psychometric analyses on nine scales included item response theory (IRT) and measurement invariance models across total Army (n = 743,057) and special operations forces (SOF; n = 3,478) cohorts. Predictive analyses examined demographic-adjusted associations between GAT scales and one-year incident medical non-readiness (MNR). Most scales had adequate reliability, although some exhibited highly skewed distributions, which likely increased measurement error. Most scales exhibited metric and scalar measurement equivalence across total Army and SOF groups. Scores from scales measuring positive characteristics were associated with lower odds of MNR (good coping, flexibility, optimism, positive affect, work engagement, friendship, organization trust; adjusted odds ratios ≤ 0.75); scores from scales measuring negative characteristics were associated with increased odds of MNR (poor sleep, depression, negative affect, loneliness; adjusted odds ratios ≥ 1.4). Associations were similar across Army and SOF cohorts. In conclusion, self-report data can potentially contribute to command surveillance, but iterative quality-checks are necessary after deployment.

Force Health Protection Education: A Pilot Approach to Applying Military Frameworks to Service Member Health Education

Ensuring Force Health Protection (FHP) is one of the most critical priorities in the DoD; however, there is no systematic approach for individual service members to address their own FHP. This paper outlines the FHP Education workshop, a model program fielded at 3rd Special Forces Group, Fort Bragg, NC, which applies military processes, principles, and frameworks to teaching special operations forces operators and enablers how to address their own FHP by identifying and mitigating threats to health and performance in the military operational environment. The FHP Education workshop has the potential to be a well-received and impactful program that offers a proactive, whole of person, community-based preventive system aligned with the Total Force Fitness framework to enable individual service members to conduct FHP.

Total Force Fitness Standardization: Leveraging Policy and Metrics to Inform and Accelerate Implementation

Total Force Fitness (TFF) metrics inform leaders at every level as they develop and evaluate policies, practices, and programs that enable soldiers, airmen, sailors, marines, guardians, and operators to achieve human performance optimization in all eight domains as defined by the TFF framework. The Standardization Workgroup was a facilitated discussion breakout session among a group of uniquely informed and engaged attendees who were invited to be part of the TFF summit that was hosted in Bethesda, Maryland, on September 14 and 15, 2021. The Standardization Workgroup explored the 2018 TFF shift in perspective to consider human performance optimization in the context of a military unit's fitness for missions and identified several challenges, opportunities, and action items for improving the implementation and sustainment of TFF throughout the services. Key opportunities and recommendations synthesized from the workgroup discussion include the following: Creating true ownership of TFF by an entity with authority and engagement across the services; creating divisions of labor and assigning champion organizations with distinct areas of responsibility related to metric development, data accessibility, line-leader decision support, and data-driven policy and program review; leveraging and expanding the use of data repositories, secure data clouds, and artificial intelligence platforms to support a robust and integrated learning health and performance system; and prioritizing the operational line-leader stakeholder engagement at every stage of metric development and refinement as they are ultimately responsible for and have direct influence over the fitness of the individual service member and readiness to deploy of the military unit.

Characterizing Relationships Among the Cognitive, Physical, Social-emotional, and Health-related Traits of Military Personnel

INTRODUCTION

Personnel engaged in high-stakes occupations, such as military personnel, law enforcement, and emergency first responders, must sustain performance through a range of environmental stressors. To maximize the effectiveness of military personnel, an a priori understanding of traits can help predict their physical and cognitive performance under stress and adversity. This work developed and assessed a suite of measures that have the potential to predict performance during operational scenarios. These measures were designed to characterize four specific trait-based domains: cognitive, health, physical, and social-emotional.

MATERIALS AND METHODS

One hundred and ninety-one active duty U.S. Army soldiers completed interleaved questionnaire-based, seated task-based, and physical task-based measures over a period of 3-5 days. Redundancy analysis, dimensionality reduction, and network analyses revealed several patterns of interest.

RESULTS

First, unique variable analysis revealed a minimally redundant battery of instruments. Second, principal component analysis showed that metrics tended to cluster together in three to five components within each domain. Finally, analyses of cross-domain associations using network analysis illustrated that cognitive, health, physical, and social-emotional domains showed strong construct solidarity.

CONCLUSIONS

The present battery of metrics presents a fieldable toolkit that may be used to predict operational performance that can be clustered into separate components or used independently. It will aid predictive algorithm development aimed to identify critical predictors of individual military personnel and small-unit performance outcomes.

Decreased Percent Body Fat but Not Body Mass is Associated with Better Performance on Combat Fitness Test in Male and Female Marines

ABSTRACT

Pletcher, ER, Lovalekar, M, Coleman, LC, Beals, K, Nindl, BC, and Allison, KF. Decreased percent body fat but not body mass is associated with better performance on the Marine Corps Combat Fitness Test. J Strength Cond Res 37(4): 887-893, 2023-The military uses a variety of physical fitness tests to assess physical readiness. The Marine Corps designed the Combat Fitness Test (CFT) to emphasize functional fitness related to operational demands. The purpose of this study was to investigate the association between body mass (BM), fat free mass (FFM), and percent body fat (BF%) measured via air displacement plethysmography with CFT performance in male and female marines. Two-hundred 10 male (22.4 ± 2.6 years) and 84 female (22.6 ± 2.8 years) marines were grouped into quintiles according to BM (in kilograms), FFM (in kilograms), and BF%. Kruskal-Wallis test or 1-way analysis of variance were used to determine if significant differences in CFT total and component scores existed between the groups of subjects classified into quintiles of BM, FFM, and BF%. No significant differences in CFT scores were observed between BM quintile in either men or women. No significant differences in CFT scores were observed between FFM quintiles in men. Total CFT score ( p = 0.002), movement to contact (MTC; p = 0.014), maneuver under fire (MANUF; p = 0.008), and ammunition lift (AL; p = 0.014) were all significantly different among FFM quintiles in women. Total CFT score ( p = 0.007), MTC ( p = 0.001), and MANUF ( p = 0.022) were significantly different among BF% quintiles in men. Total CFT score ( p = 0.008), MTC ( p = 0.033), and AL ( p = 0.016) were significantly different among BF% quintiles in women. Male and female marines in the quintile with lowest BF% had better CFT scores than those in higher quintiles. Targeted physical training and nutrition considerations to optimize BF% may help improve military task performance.

Physiological biomarker monitoring during arduous military training: Maintaining readiness and performance

OBJECTIVES

Physiological and psychological stressors can degrade soldiers' readiness and performance during military training and operational environments. Integrative and holistic assessments of biomarkers across diverse human performance optimization domains during multistressor training can be leveraged to provide actionable insight to military leadership regarding service member health and readiness.

DESIGN/METHOD

A broad categorization of biomarkers, to include biochemical measures, bone and body composition, psychometric assessments, movement screening, and physiological load can be incorporated into robust analytical pipelines for understanding the complex factors that impact military human performance.

RESULTS

In this perspective commentary we overview the rationale, selection, and methodologies for monitoring biomarker domains that are relevant to military research and specifically highlight methods that have been incorporated in a research program funded by the Office of Naval Research, Code 34 Biological and Physiological Monitoring and Modeling of Warfighter Performance.

CONCLUSIONS

The integration of screening and continuous monitoring methodologies via robust analytical approaches will provide novel insight for military leaders regarding health, performance, and readiness outcomes during multistressor military training.

Characterising Psycho-Physiological Responses and Relationships during a Military Field Training Exercise

Over a 15-day period, that included an eight-day field trial, the aims of this study were to (1) quantify the physical workload, sleep and subjective well-being of soldiers in training; (2a) Explore relationships between workload and well-being, and (2b) sleep and well-being; (3) Explore relationships between workload, sleep, and well-being.

METHODS

Sixty-two Combat Engineer trainees (59 male, 3 female; age: 25.2 ± 7.2 years) wore an ActiGraph GT9X to monitor daily energy expenditure, physical activity, and sleep. Rating of perceived exertion (RPE), sleep quality, and fatigue were measured daily, subjective well-being was reported days 1, 5, 9, 13 and 15. Multi-level models were used for the analysis.

RESULTS

Well-being was affected by a combination of variables including workload, subjective sleep quality, sleep duration, and sleep efficiency. RPE and subjective sleep quality were consistently significant parameters within the models of best fit.

CONCLUSIONS

Perceptions of well-being were lower during the field training when physical workload increased, and sleep decreased. Energy expenditure was comparatively low, while daily sleep duration was consistent with field training literature. Subjective assessments of workload and sleep quality were consistently effective in explaining variations in well-being and represent an efficient approach to monitor training status of personnel.

Relationship between a Maximum Plank Assessment and Fitness, Health Behaviors, and Moods in Tactical Athletes: An Exploratory Study

A maximum plank hold (PH) has been implemented in the Army Combat Fitness Test (ACFT) with the Holistic Health and Fitness (H2F) program. The H2F program introduces a shift in wellbeing from a fitness centered approach to framework also comprising nutrition, sleep, mental, and spiritual components. The purpose was to analyze how a maximum PH correlated with fitness, lifestyle behaviors, and mood states in tactical athletes (TA) and assess differences between those who pass and fail. Forty-nine TA completed fitness testing, lifestyle behavior, and mood state surveys. Bivariate correlations were used to examine relationships with PH performance. PH time was significantly correlated with total body mass, fat mass, BMI, push-ups, and state physical energy (SPE). VO_2max was significantly different between the groups who passed and failed the PH. PH was not associated with lifestyle behaviors or trait mood states. PH performance could vary day-to-day as it was correlated with SPE. Individuals with poorer aerobic fitness and body composition may be at risk for failing the PH.

Factors Predicting Training Delays and Attrition of Recruits during Basic Military Training

Ensuring a balance between training demands and recovery during basic military training (BMT) is necessary for avoiding maladaptive training responses (e.g., illness or injury). These can lead to delays in training completion and to training attrition. Previously identified predictors of injury and attrition during BMT include demographic and performance data, which are typically collected at a single time point. The aim of this study was to determine individual risk factors for injury and training delays from a suite of measures collected across BMT. A total of 46 male and female recruits undertaking the 12-week Australian Army BMT course consented to this study. Injury, illness, attrition, and demographic data were collected across BMT. Objective measures included salivary cortisol and testosterone, step counts, cardiorespiratory fitness, and muscular endurance. Perceptions of well-being, recovery, workload, fatigue, and sleep were assessed with questionnaires. Baseline and mean scores across BMT were evaluated as predictors of injury and attrition using generalized linear regressions, while repeated-measures ANOVA was used for the group comparisons. From the 46 recruits, 36 recruits completed BMT on time; 10 were delayed in completion or discharged. Multiple risk factors for injury during BMT included higher subjective ratings of training load, fatigue, and stress, lower sleep quality, and higher cortisol concentrations. Higher ratings of depression, anxiety, and stress, and more injuries were associated with a higher risk of delayed completion. Higher concentrations of testosterone and higher levels of fitness upon entry to BMT were associated with reduced risk of injury and delayed completion of BMT. Ongoing monitoring with a suite of easily administered measures may have utility in forewarning risk of training maladaptation in recruits and may complement strategies to address previously identified demographic and performance-based risk factors to mitigate injury, training delays, and attrition.

Resilience, Psychological Stress, Physical Activity, and BMI among United States Air National Guardsmen: The COVID-19 Pandemic

Background

Military service members carry the responsibility to maintain physical and psychological readiness. As such, it is critical for researchers to begin unravelling the widespread impact of the COVID-19 pandemic on service member’s mental and physical wellbeing. The aim of this research was to investigate the complex relationships between BMI, physical activity, psychological stress and resilience among United States Air National Guardsmen (USANG), specifically during the pandemic.

Methods

An online survey was distributed to USANG members. The survey included measures of resilience (CD-RISC-25), perceived psychological stress (PSS), perceived psychological stress brought on by COVID-19 (COVID-19 PSL), current levels of physical activity (IPAQ-SF), perceived impact on physical activity brought on by COVID-19 (COVID-19 PAL), and BMI. Pearson’s correlation coefficients (r) were used to assess correlation significance (α ≤ 0.05), direction, and magnitude.

Results

A total of 110 responses met inclusion criteria for data interpretation. A majority reported a decline in physical activity 54.5%, while 60% reported an increase in psychological stress. According to BMI classifications, 60.9% were considered overweight or obese. Seven meaningful (effect size ≥ |2.0|) and statistically significant salient associations were identified resilience-PSS r = -0.38; resilience-COVID-19 PAL r = 0.21; PSS-COVID-19 PSL r = 0.35; PSS-COVID-19 PAL r = -0.23; COVID-19 PSL COVID-19 PAL r = -0.24; IPAQ-SF-BMI r = -0.23; BMI-Covid-19 PAL r = -0.32.

Conclusion

Key outcomes suggest resilience is inversely associated with assessed and perceived stress, resilience may influence health-related behaviour which subsequently might aid as a protective factor against psychological stress. Knowledge regarding the relationships between the aforementioned variables may help inform decisions by military leadership regarding future lockdowns.

Exercise blood-drop metabolic profiling links metabolism with perceived exertion

Background: Assessing detailed metabolism in exercising persons minute-to-minute has not been possible. We developed a "drop-of-blood" platform to fulfill that need. Our study aimed not only to demonstrate the utility of our methodology, but also to give insights into unknown mechanisms and new directions. Methods: We developed a platform, based on gas chromatography and mass spectrometry, to assess metabolism from a blood-drop. We first observed a single volunteer who ran 13 km in 60 min. We particularly monitored relative perceived exertion (RPE). We observed that 2,3-bisphosphoglycerate peaked at RPE in this subject. We next expanded these findings to women and men volunteers who performed an RPE-based exercise protocol to RPE at Fi O ₂ 20.9% or Fi O ₂ 14.5% in random order. Results: At 6 km, our subject reached his maximum relative perceived exertion (RPE); however, he continued running, felt better, and finished his run. Lactate levels had stably increased by 2 km, ketoacids increased gradually until the run's end, while the hypoxia marker, 2,3 bisphosphoglycerate, peaked at maximum relative perceived exertion. In our normal volunteers, the changes in lactate, pyruvate, ß hydroxybutyrate and a hydroxybutyrate were not identical, but similar to our model proband runner. Conclusion: Glucose availability was not the limiting factor, as glucose availability increased towards exercise end in highly exerted subjects. Instead, the tricarboxylic acid→oxphos pathway, lactate clearance, and thus and the oxidative capacity appeared to be the defining elements in confronting maximal exertion. These ideas must be tested further in more definitive studies. Our preliminary work suggests that our single-drop methodology could be of great utility in studying exercise physiology.

Prioritized research recommendations and potential solutions: addressing gaps surrounding dietary supplement ingredients for boosting brain health and optimizing cognitive performance

In the market of dietary supplements, a low level of certainty exists in the state of the science, coupled with not always knowing what is in the product. Together these issues make weighing benefits/risks difficult and hinder the ability to guide evidence-based practice decisions. The authors sought to identify priorities and develop potential solutions to address research gaps so that information disseminated, can ultimately, be relied upon, when trying to make appropriate and safe decisions. Using a modified-Delphi process, 8 panelists reviewed evidence, provided from systematic review, on dietary supplement ingredients for brain health, and prioritized gaps identified and offered potential solutions. Research gaps specific to dietary supplements research included the need for quality testing of products, the question of bioavailability and absorption of ingredients, and optimal composition and standardization of supplements under investigation. Other gaps related to populations studied; a general sense of bias towards focusing research on diseased rather than maintaining or optimizing performance in healthy populations. Additionally, the lack of uniform cognitive performance measures and metrics used across research is a gap, as well as whether the metrics are accurate representations of or even generalizable to "real-life" participants wishing to optimize their performance. Methodological quality and ethical concerns in the conduct and reporting of science encompass all issues. If resources map to potential solutions outlined in this paper, then these proposed next steps offered will help facilitate meaningful research, move evidence into practice recommendations, and ultimately develop better decision-making tools for consumers to trust and rely upon for making safe supplement decisions.

Associations between inflammatory markers and well-being during 12 weeks of basic military training

PURPOSE

Stress, anxiety and physical exertion are all closely linked to well-being, and each can alter immune function. Diminished well-being has been observed during military training, however there is mixed evidence regarding whether concomitant changes in inflammatory markers occur, with these phenomena indicating potential maladaptive responses to imposed training loads. The aims of this project were (1) assess changes in inflammation and subjective well-being across a 12-week basic military training (BMT) program, and (2) evaluate relationships between circulating inflammatory markers and well-being.

METHODS

A total of 37 men and women undergoing 12 weeks of BMT in Australia were recruited. Well-being was assessed via questionnaire (DASS-21), and plasma samples were collected for the analysis of inflammatory cytokines [interleukin (IL)-4, IL-6, IL-1β, IL-8, IL-10, and tumor necrosis factor (TNF)-α] at weeks 1, 4, 8 and 12. Data were analysed using general linear mixed models.

RESULTS

Depression, anxiety and stress subscale scores all significantly improved (all P ≤ 0.001), and TNF-α decreased (P = 0.031) across time. Compared to baseline (week 1), significant decreases in associations between depression and IL-10, anxiety and IL-10, and stress and IL-10, IL-4 IL-6 and TNF-α (all P < 0.05), were detected across BMT.

CONCLUSION

The BMT program appears to support improved well-being over the 12 weeks, with minimal perturbation to inflammatory markers. Biomarkers and well-being displayed consistent associations and may have utility as psychophysiological indicators of health status in military research, however for now, subjective measures may represent more cost-effective proxies for ongoing monitoring of military personnel.

Healthy Eating Index and Nutrition Biomarkers among Army Soldiers and Civilian Control Group Indicate an Intervention Is Necessary to Raise Omega-3 Index and Vitamin D and Improve Diet Quality

Diet quality and nutrition status are important for optimal health and military performance. Few studies have simultaneously evaluated diet quality and biochemical markers of nutritional status of military service members. The Healthy Eating Index (HEI) can be used to assess dietary quality and adherence to federal nutrition guidelines. The aim of this study was to assess soldiers' diet quality and nutritional status and compare results to a civilian control group.

METHODS

A cross-sectional study was conducted with 531 soldiers. A food frequency questionnaire was used to calculate HEI scores. A blood sample was collected for analysis of select nutrition biochemical markers. Non-parametric analyses were conducted to compare the diet quality and nutritional status of soldiers and controls. Differences in non-normally distributed variables were determined by using the Wilcoxon signed-rank test.

RESULTS

Soldiers had an HEI score of 59.9 out of 100, marginally higher than the control group (55.4). Biochemical markers of interest were within normal reference values for soldiers, except for the omega-3 index and vitamin D.

CONCLUSIONS

This study identified dietary components that need improvement and deficits in biochemical markers among soldiers. Improving diet quality and nutritional status should lead to better health, performance, and readiness of the force.

The Overtraining Syndrome in Soldiers: Insights from the Sports Domain

INTRODUCTION

Soldiers are exposed to extreme training regimens in order to optimally prepare for real battle. High attrition rates are a known issue during training courses, especially for elite troops. An underlying factor might be the disbalance between stress/strain and recovery. The aim of this review is to give insight in the current knowledge about functional overreaching (FOR), non-FOR (NFOR), and the overtraining syndrome (OTS) in the military.

MATERIALS AND METHODS

A systematic literature review was conducted. PubMed, IngentaConnect, Science Direct, and Web of Science were screened for the following keywords and combinations of search terms; military, personnel, OT, soldier.

RESULTS

Seven studies investigating the effects of OT during training courses were selected. The definitions used for OT varied widely and there is no systematic use of markers to determine FOR, NFOR, or the OTS in the military.

CONCLUSIONS

Much research on NFOR/OTS has been conducted in the sports domain and the military could make use of these insights to promote a more efficient balance between training load and recovery. It is suggested to regularly test soldiers on physical performance, psychomotor speed and mood using ideally a military-specific test or the 1.5-mile run, psychomotor vigilance test and Profile of Mood States. The two-bout exercise test can be used as a specific test if previous testing indicates the development of NFOR/OTS and can be combined with metabolic and immunological testing to exclude pathological causes.

A Z-score based method for comparing the relative sensitivity of behavioral and physiological metrics including cognitive performance, mood, and hormone levels

A method for assessing the relative sensitivity of research metrics is proposed and illustrated by comparing 18 outcome measures from a published study of the cognitive, mood, and hormonal effects of four different levels of stress induced by intense military training. Research on the human response to stress often assesses multiple disparate dependent measures. Selecting the most sensitive is difficult as formal methods to compare varied dependent measures have not been developed. The method first converts the outcome measures into standard scores (z-scores) and then compares them using analysis of variance to determine whether there are differences in how they assess the impact of graded levels of exposure to stress. The analysis detected various significant interactions in several measures and suggests self-report mood questionnaires were more sensitive to the stressors present in the study than the cognitive or hormonal measures which were used. These findings support the effectiveness of the z-score based method as a useful procedure for objectively evaluating the differential sensitivity of various metrics. This method could be useful for research on other independent variables when use of multiple assessment strategies is appropriate. It could be used for evaluating studies yielding conflicting results, such as those detecting effects on one parameter but not others. In such instances, cross-metric inconsistencies may be due to differential sensitivity of measurement strategies rather than actual differences in the effects of the independent-variable on the domains under investigation.

The Warrior Model for Human Performance Optimization

Special Operations Combat Personnel (SOCP) face significant challenges and occupational demands that put them at significant risk for musculoskeletal injury. Musculoskeletal injury leads to lost-duty days, medical disqualification, and compromises operational readiness and mission success. Optimizing human performance and developing injury prevention strategies can position SOCP for success, but human performance optimization is a complex process that demands the integration of multiple disciplines to address a broad range of capabilities necessary for this success. The Warrior Model for Human Performance Optimization outlines a step-by-step approach to human performance optimization embedded within a scientific, evidenced-based approach to injury prevention and performance optimization that includes a step to ensure specificity of training and interventions. This evidence-based approach can insure that SOCP capabilities match the demands of occupation enabling them to successfully execute their occupation tasks without risk of injury. While the focus of this review is on military personnel, the same principles have application to nonmilitary high-performance athletes.

Physical Fitness Predictors of a Warrior Task Simulation Test

Huang, H-C, Nagai, T, Lovalekar, M, Connaboy, C, and Nindl, BC. Physical fitness predictors of a warrior task simulation test. J Strength Cond Res 32(9): 2562-2568, 2018-The warrior task simulation test (WTST) has been developed in an attempt to better assess physical fitness required for soldiers to perform battlefield tasks and drills to determine whether laboratory-based measurements of physical fitness components could be used to predict the WTST. Forty-three healthy and physically active men participated in 2 sessions: the WTST and laboratory testing. The WTST comprised 282-m run, low hurdles, high crawl, casualty drag, balance beam, point-aim-move, 100-yard sprint, and agility sprint with participants wearing combat boots, uniform, helmet, and dummy rifle. The laboratory testing included assessments of participants' muscular strength and endurance, postural stability, aerobic capacity, anaerobic capacity, flexibility, body fat, fat-free mass, and agility. Correlation and simple and multiple linear regression analyses were used to analyze the relationship between the WTST and laboratory testing and predict the WTST, respectively (p < 0.05). The correlation and the simple linear regression analyses revealed that anaerobic capability, aerobic capacity, body fat, agility, and muscular endurance correlated with (r = 0.35-0.59) and accounted for 12-34% of the variance in (R = 0.12-0.34) the WTST performance (p < 0.05). The final model included aerobic capacity, agility, fat-free mass, muscular endurance, and body fat (R = 0.52, p < 0.001). The current results highlighted the importance of several components of physical fitness in simulated battlefield tasks and drills (assessed by the WTST). In particular, anaerobic capacity, aerobic capacity, and body fat had the highest correlational and predictive values of the WTST. Additionally, skill-related components of physical fitness, such as agility and muscular endurance, should not be ignored, and they should be assessed and tracked with the above-mentioned components.

International consensus on military research priorities and gaps - Survey results from the 4th International Congress on Soldiers' Physical Performance

OBJECTIVES

The objectives of this study were to identify perceived priorities related to military personnel's health and physical performance, among attendees at the 4th International Congress on Soldiers' Physical Performance (ICSPP), and to determine if perceived priorities had changed between the 3rd ICSPP survey held in 2014 and the 4th ICSPP survey held in 2017.

DESIGN

Electronic survey.

METHODS

Respondents were asked to grade priority areas on a Likert scale, and average ratings were used to rank priority areas. Responses to free text questions were analyzed qualitatively. Responses to the 4th ICSPP survey were described and compared to responses to the 3rd ICSPP survey.

RESULTS

The 4th ICSPP survey respondents were a diverse group (40.6% military, 58.9% civilian). The two most important priority areas identified were physical demands in operational environments (mean score=4.41/5) and measuring physical performance/fitness (4.38/5), which were also the top two areas in the 3rd ICSPP survey. There was remarkable overlap in the rankings of priority areas between the two surveys. Sleep and nutrition were emerging priority areas and were perceived as relatively more important in the 4th ICSPP survey compared to the 3rd ICSPP survey. The greatest perceived emerging threat was resilience/psychological fitness of recruits (4.16/5). Physiological status monitoring (2.79/4) was identified as the most important technology.

CONCLUSIONS

Despite the diverse backgrounds of the respondents, there was a clear continuing consensus about perceived important priority areas influencing military personnel's health and physical performance. Soldier resiliency and assessment of physiological status were research topics identified as top priorities.

Functional physical training improves women's military occupational performance

The U.S. Armed Forces have recently approved full integration of women into combat roles. Physical fitness demands for executing Military Occupational Specialties (MOS) are substantial; thus lifting and load carriage capability improvements are desirable.

OBJECTIVES

To determine if a specially-designed physical conditioning program could lessen the gap between the performance of male and female Soldiers in lifting and load carriage and thereby enable women to meet the requirements of most, if not all, Army MOSs.

METHODS

Forty women participated in a 24-week physical training program, which included resistance training, long-distance running, backpacking, and specialized drills. Pre- and post-tests of occupational and physical performance measures were conducted before and after training. Repeated measures analysis of variance were used to determine statistically significant differences among the pre-, mid- and posttests.

RESULTS

Women increased maximal occupational lifting strength 12-20 kg, added 9-34 repetitions in lifting endurance, increased 0.23 m in jumping performance, added 46 repetitions in local muscular endurance, and decreased load carriage for time by 3.7-8.6 min. Women scored within 82-94% of untrained male scores for aerobic capacity and muscular endurance after training.

CONCLUSION

Women's ability to perform physically-demanding military occupational tasks was significantly improved following 6 months of concurrent training, with emphasis on load carriage and lifting. The percentage of women that qualified for current "heavy" and "very heavy" MOSs was initially 24%, but increased to 78% after training. A resistance training program of 6+ months can adequately prepare women for "heavy" to "very heavy" MOS's.

Far-Forward Diagnostics in Toxic Industrial Chemical and Material Exposure Scenarios and Biomarker Identification

: This study describes key technical solutions for detecting environmental toxicants and diagnosing adverse health effects in military operational settings as outlined at a symposium cosponsored by the Department of Defense and the Johns Hopkins University-Applied Physics Laboratory (October 27 to 28, 2015). Such technologies are urgently needed in order to provide critical decision-aid tools and prognostic assessment of potential clinical sequelae. This review summarizes the state-of-the-science on (1) prioritization of adverse health effects, (2) existing technologies and diagnostic tools available for use in theater, (3) challenges to advancing diagnostic tools far-forward, and (4) the potential utility of anchoring diagnostic tools to adverse outcome pathways. Emerging technologies are increasingly available for physiological, environmental, and individual exposure monitoring. Challenges to overcome in austere environments include cold chain requirements and determination of adequate sampling intervals.