The Tactical Athlete: Definitions, Cardiovascular Assessment, and Management, and "Fit for Duty" Standards

Tactical athletes are individuals in the military, law enforcement, and other professions whose occupations have significant physical fitness requirements coupled with the potential for exposure to life-threatening situations. Such exposures can have varied hemodynamic effects on the cardiovascular system. It is crucial that their clinical evaluation is inclusive of specific occupational requirements. Safety protocols regarding medical clearance are relatively more stringent for this population than for competitive athletes due to the increased impact to the tactical athlete, their team, and the population they aim to serve and protect should they experience a cardiovascular event on the job.

Exercise self-efficacy remains unaltered during military service

Background

Exercise self-efficacy is a crucial aspect of adopting and maintaining a physically active lifestyle. Regular physical activity may enhance exercise self-efficacy. This study aimed to investigate the baseline associations of physical fitness, physical activity, and body composition with exercise self-efficacy and the effects of military service on exercise self-efficacy. Methods: The sample consisted of healthy young Finnish conscripts (n = 243) undergoing military service. The participants were divided into two groups: an intervention group undergoing a high-intensity functional training program (n = 113) and a control group undergoing traditional physical training within their military service (n = 130). Exercise self-efficacy (adoption and barrier) and aerobic and muscular fitness were measured thrice (baseline, month 3, and month 5). Self-reported leisure-time physical activity and measured fat percentage were collected at baseline.

Results

Adoption and barrier exercise self-efficacy correlated positively with aerobic and muscular fitness and leisure time physical activity (r = 0.33-0.59, p < 0.001), and barrier self-efficacy negatively with fat percentage (r = -0.15, p < 0.05) at baseline. No changes in adoption (time p = 0.912) and barrier self-efficacy (time p = 0.441) occurred during the military service. There were no differences between groups in these changes (group × time interaction p = 0.643 for adoption self-efficacy and p = 0.872 for barrier self-efficacy). Change in muscular fitness correlated positively with change in barrier self-efficacy in the high-intensity functional training group (r = 0.35, p < 0.05). Conclusions: Exercise self-efficacy is positively associated with physical fitness and physical activity among young males. However, military service, whether it involves high-intensity functional physical training or more diverse traditional physical training, does not improve exercise self-efficacy.

An observational objective job analysis of role related tasks undertaken by Royal Navy sailors

BACKGROUND

The current in-service Royal Naval Fitness Test has two elements to test the aerobic endurance and muscular strength of Service Personnel through generic field-based tests and a short job task simulation. However, in 2017 the Royal Navy (RN) identified a requirement to update their in-service fitness test to align with international best practice.

OBJECTIVE

The purpose of this study was to conduct an Objective Job Task Analysis on critical, physically demanding tasks that could be undertaken by RN sailors during sea deployments.

METHODS

Twenty-one training exercises were observed across a range of contexts; Type 23 Frigates, Type 45 Destroyers and at shore-based training facilities. A total of 203 RN personnel (age 27.8±7.1 years) were observed undertaking 36 job related tasks (e.g., 'firefighting', 'damage control', 'abandon ship' and 'casualty handling'). Tasks were evaluated by cardiovascular response, primary functional movements and contextual factors to aid a Military Judgement Panel in task list down-selection.

RESULTS

14 Criterion Tasks (e.g., 'firefighting', 'two-person magazine stowage' and 'casualty handling') were selected to progress to the next stage of the process. Five tasks were selected based on cardiovascular responses and a further nine tasks selected based on task ergonomics and other factors.

CONCLUSION

This research has identified and quantified the most physically demanding, critical roles undertaken by RN sailors on sea deployments and will inform the development of the RN Physical Employment Standard.

Changes in physical performance, body composition and physical training during military operations: systematic review and meta-analysis

Systematic review and meta-analysis applying PRISMA guidelines with a PICOS format was constructed to provide an overview of changes in physical performance, body composition and physical training in soldiers during prolonged (≥ 3 months) military operations. Twenty-four studies out of the screened 4431 records filled the inclusion criteria. A small decrease in endurance performance was the most consistent finding (Hedge's g [g] - 0.21, 95% CI - 0.01 to - 0.41) while small overall increases in maximal strength of the lower (g 0.33, 95% CI 0.16-0.50) and upper body (g 0.33, 95% CI 0.19-0.46) were observed. In addition, small increases in strength endurance (push-up, g 0.34, 95% CI 0.15-0.52; sit-up g 0.26, 95% CI 0.07-0.44) were observed. The overall changes in body composition were trivial. Heterogeneity in the outcome variables varied mainly between low to moderate. Large inter-individual variations were observed in physical training volume, including decrements especially in endurance training frequency and volume. A reduction in total training load was often associated with negative changes in body composition and physical performance according to the principle of training specificity. Individuals with higher initial fitness level were more susceptible to decrements in their physical performance during operation.

Physiological and physical performance changes during a 20-day winter military training course and its subsequent 10-day recovery period

The present study investigated physiological, mental and physical performance changes during a 20-day winter military training course and the following 10-day recovery period. Fifty-eight (age 19 ± 1 years, height 182 ± 6 cm, body mass 78.5 ± 7.2 kg) male soldiers volunteered. Body composition, serum biomarker levels and performance tests were measured four times during the study. In addition, questionnaires were collected daily for subjective stress and rate of perceived exertion. The course induced significant declines in body (-3.9%, p < 0.05) and fat mass (-31.6%, p < 0.05) as well as in all assessed physical performance variables (-9.2 - -20.2%, p < 0.05), testosterone (-73.7%, p < 0.001) and IGF-1 concentrations (-43.6%, p < 0.001). At the same time, the sex hormone-binding globulin, creatine kinase, and C-reactive protein values increased significantly (46.3-1952.7%, p < 0.05). After the 10-day recovery period, the body composition and hormonal values returned to the baseline (p < 0.05), as did some physical performance variables, such as 2 min sit-ups and the evacuation test (p < 0.05). However, explosive force production in the upper and lower bodies remained unrecovered. The 20-day winter military training caused significant physiological and mental stress, as well as a drastic decline in physical performance even for highly physically fit soldiers, and the 10-day recovery period did not establish full recovery.

High-Intensity Functional Training Induces Superior Training Adaptations Compared With Traditional Military Physical Training

ABSTRACT

Helén, J, Kyröläinen, H, Ojanen, T, Pihlainen, K, Santtila, M, Heikkinen, R, and Vaara, JP. High-intensity functional training induces superior training adaptations compared with traditional military physical training. J Strength Cond Res 37(12): 2477-2483, 2023-This study examined the effectiveness of concurrent strength and endurance training with an emphasis on high-intensity functional training (HIFT) during military service. Voluntary male conscripts (aged 18-28 years) were placed in either an experimental (EXP: n = 50-66) or a control (CON: n = 50-67) group. The training for the EXP group included HIFT using body mass, sandbags, and kettlebells. The CON group trained according to the current practice. Physical performance and body composition were assessed at baseline (PRE), at week 10 (MID), and after (POST) the 19-week training period. Significance was set at p < 0.05. The total distance covered in a 12-minute running test increased in both groups, but the change in EXP was superior to the change in CON (11.6%, ES: 0.79 vs. 5.7%, ES: 0.33; p = 0.027). Maximal strength and power characteristics increased in EXP (3.1-5.0%), whereas no improvements were observed in CON. Conscripts with the highest initial fitness showed no improvements in physical performance in either group. Body mass and waist circumference decreased in EXP, whereas CON showed an increase in muscle mass. These findings suggest that HIFT is an effective and time-efficient approach to improve soldiers' aerobic fitness during military service. For the optimal development of strength, the training equipment used may not have provided sufficient and progressive loading to yield considerable strength adaptations. More focus should be placed on sufficient intensity and volume in both strength and endurance training, especially for the most fit soldiers.

Performance nutrition for cold-weather military operations

.High daily energy expenditure without compensatory increases in energy intake results in severe energy deficits during cold-weather military operations. The severity of energy deficits has been proportionally linked to declines in body mass, negative protein balance, suppression of androgen hormones, increases in systemic inflammation and degraded physical performance. Food availability does not appear to be the predominant factor causing energy deficits; providing additional rations or supplement snack bars does not reduce the severity of the energy deficits. Nutrition interventions that allow greater energy intake could be effective for reducing energy deficits during cold-weather military operations. One potential intervention is to increase energy density (i.e. energy per unit mass of food) by increasing dietary fat. Our laboratory recently reported that self-selected higher energy intakes and reductions in energy deficits were primarily driven by fat intake (r = 0.891, r² = 0.475), which, of the three macronutrients. Further, soldiers who ate more fat lost less body mass, had lower inflammation, and maintained net protein balance compared to those who ate less fat. These data suggest that consuming high-fat energy-dense foods may be a viable nutritional intervention that mitigates the negative physiological effects of energy deficit and sustains physical performance during cold-weather military operations.

Effects of 12-Month Training Intervention on Physical Fitness, Body Composition, and Health Markers in Finnish Navy Soldiers

BACKGROUND

Most Western adults do not meet the recommendations for sufficient activity, and obesity is a global problem. Similar trends are also seen among Western military personnel. Many successful physical training interventions have been carried out in military environments, but the interventions have been quite short term, and the training has been supervised. Therefore, the aim of this study was to investigate the effects of a 12-month voluntary motivational training intervention among the Finnish Defence Forces' (FDF) Navy soldiers.

METHODS

In total, 77 FDF Navy soldiers, serving in missile patrol boats, took part in the study. The intervention group (IG) contained 45 participants and the control group (CG) contained 32 participants. The IG was divided into four teams that carried out the intervention, while the CG took part in only the measurements.

RESULTS

Most of the participants (65%) in the IG reported that they had increased their exercise volume during the intervention, but no major beneficial impacts on the physical fitness, body composition, or health markers were observed. Nevertheless, there was a clear diversity visible between the subgroups in the IG. The team that reported the most exercise had the best motivation and the most motivated team coach and also had the most improved physical fitness and body composition results.

CONCLUSIONS

The present study points out that in military environments, long-term voluntary training interventions may not be as successful as short-term supervised interventions. The results also suggest that in voluntary training interventions among military personnel, the participants' motivation to exercise is a key factor when improving physical fitness.

Maintaining soldier musculoskeletal health using personalised digital humans, wearables and/or computer vision

OBJECTIVES

The physical demands of military service place soldiers at risk of musculoskeletal injuries and are major concerns for military capability. This paper outlines the development new training technologies to prevent and manage these injuries.

DESIGN

Narrative review.

METHODS

Technologies suitable for integration into next-generation training devices were examined. We considered the capability of technologies to target tissue level mechanics, provide appropriate real-time feedback, and their useability in-the-field.

RESULTS

Musculoskeletal tissues' health depends on their functional mechanical environment experienced in military activities, training and rehabilitation. These environments result from the interactions between tissue motion, loading, biology, and morphology. Maintaining health of and/or repairing joint tissues requires targeting the "ideal" in vivo tissue mechanics (i.e., loading and strain), which may be enabled by real-time biofeedback. Recent research has shown that these biofeedback technologies are possible by integrating a patient's personalised digital twin and wireless wearable devices. Personalised digital twins are personalised neuromusculoskeletal rigid body and finite element models that work in real-time by code optimisation and artificial intelligence. Model personalisation is crucial in obtaining physically and physiologically valid predictions.

CONCLUSIONS

Recent work has shown that laboratory-quality biomechanical measurements and modelling can be performed outside the laboratory with a small number of wearable sensors or computer vision methods. The next stage is to combine these technologies into well-designed easy to use products.

The Influence of Previous Lifestyle on Occupational Physical Fitness in the Context of Military Service

The Estonian Defense Forces are the basis of military service, mandatory for all male citizens of the Republic of Estonia who are at least 17 years old. The physical load in military service, especially in the first stage, is significantly greater than for men in everyday life. Therefore, it is important to know if health promotion in civilian life adequately prepares young people for military service and to what extent pre-military health behaviors affect physical performance during service. The purpose of this work was to examine conscripts' physical fitness at different stages of military service and its relationships with previous lifestyle. Soldiers' physical fitness was estimated three times during military service using three tests: sit-ups, push-ups and 2-mile run. Lifestyle and socio-economic background data was collected by a web-based questionnaire (n = 235). Linear regression analysis was performed using Army Physical Fitness Test (APFT) scores as dependent variables and questionnaire data as independent variables. The socio-economic background variables had no effect on physical fitness scores throughout the training period (p > 0.05). Young men that were physically more active daily, did sports, had healthier diet and did not smoke before entering military service showed better physical fitness test results throughout the period of service (p < 0.05). The effect of participation in sports was evident, as the conscripts with previous sports experiences demonstrated higher fitness tests scores (p < 0.01). These findings show that health promotion initiatives or programs for promoting physical activity and healthy diet, and preventing obesity and tobacco use, can also have a positive effect on the physical performance of young men during military service.

Do the Lower Body Strength Assessment Tests in the Spanish Navy Really Measure What They Purport to Measure?

The main objective of this research was to analyse the efficacy of lower body strength assessment tests in the Armed Forces Physical Assessment System. Secondly, it was to determine what relationship exists between the physical evaluation system of the Spanish Armed forces and standardized evaluation protocols (Gold standard). A total of 905 students enrolled in the military/civil bachelor’s degree (813 male and 92 female) participated in this study. The influence of the sex of the participants was studied through the student’s t-test for independent data, and the degree of association between variables was defined by Pearson’s correlation coefficient. The results present moderate correlations (r = 0.67, r = 0.66; p < 0.001) between the vertical jump test used by the Army and the power or elastic force tests commonly used in practice and in research. The results obtained reflect a moderate relationship between the gold standard tests and the tests used by the Army, which suggests that the tests currently used to assess lower body strength should be adapted to more objective measurement tools which would allow a better comparison between samples from different armed forces.

Military Body Composition Standards and Physical Performance: Historical Perspectives and Future Directions

ABSTRACT

Harty, PS, Friedl, KE, Nindl, BC, Harry, JR, Vellers, HL, and Tinsley, GM. Military body composition standards and physical performance: historical perspectives and future directions. J Strength Cond Res 36(12): 3551-3561, 2022-US military physique and body composition standards have been formally used for more than 100 years. These metrics promote appropriate physical fitness, trim appearance, and long-term health habits in soldiers, although many specific aspects of these standards have evolved as evidence-based changes have emerged. Body composition variables have been shown to be related to many physical performance outcomes including aerobic capacity, muscular endurance, strength and power production, and specialized occupational tasks involving heavy lifting and load carriage. Although all these attributes are relevant, individuals seeking to improve military performance should consider emphasizing strength, hypertrophy, and power production as primary training goals, as these traits appear vital to success in the new Army Combat Fitness Test introduced in 2020. This fundamental change in physical training may require an adjustment in body composition standards and methods of measurement as physique changes in modern male and female soldiers. Current research in the field of digital anthropometry (i.e., 3-D body scanning) has the potential to dramatically improve performance prediction algorithms and potentially could be used to inform training interventions. Similarly, height-adjusted body composition metrics such as fat-free mass index might serve to identify normal weight personnel with inadequate muscle mass, allowing for effective targeted nutritional and training interventions. This review provides an overview of the origin and evolution of current US military body composition standards in relation to military physical readiness, summarizes current evidence relating body composition parameters to aspects of physical performance, and discusses issues relevant to the emerging modern male and female warrior.

Utility of extracellular vesicles as a potential biological indicator of physiological resilience during military operational stress

Extracellular vesicles (EVs) transport biological content between cells to mediate physiological processes. The association between EVs and resilience, the ability to cope with stress, is unknown. Using unbiased machine learning approaches, we aimed to identify a biological profile of resilience. Twenty servicemen (27.8 ± 5.9 years) completed the Connor Davidson Resilience (CD‐RISC) questionnaire and were exposed to daily physical and cognitive exertion with 48‐hr sleep and caloric restriction. Blood samples from baseline and the second day of stress were analyzed for neuroendocrine biomarkers impacted by military stress. EVs were isolated from plasma and stained with antibodies associated with exosomes (CD63), microvesicles (VAMP3), and apoptotic bodies (THSD1). Individuals were separated into high (n = 10, CD‐RISC > 90) and low (n = 10, CD‐RISC < 79) resilience. EV features were stratified by size, then down‐selected using regression trees and compared between groups. Diagnostic accuracy was assessed using receiver operating characteristic curves. Compared to low resilience, high resilience demonstrated a greater increase in variability of THSD1 local bright spot intensities among large‐sized EVs in response to stress (p = 0.002, Hedges’ g = 1.59). Among medium‐sized EVs, high resilience exhibited a greater decrease in side scatter intensity (p = 0.014, Hedges’ g = 1.17). Both features demonstrated high to moderate diagnostic accuracy for high resilience (AUC = 0.90 and 0.79). In contrast, neuroendocrine biomarker concentrations were similar between groups. The increase in variability among THSD1 + EVs in high, but not low, resilient individuals following stress may suggest high resilience is accompanied by stress‐triggered apoptotic adaptations to the environment that are not detected in neuroendocrine biomarkers.

New Training Program for the New Requirements of Combat of Tactical Athletes

Actual theaters of operations are complex contexts where soldiers must face different situations, such as symmetrical, asymmetrical, or close quarter combat. The requirements of the actual battlefield are different to the traditional conditioning military training. This new changing scenario produces an activation of the innate fight or flight defense mechanisms with large activations of the anaerobic metabolic pathways and the sympathetic autonomic nervous system. In these scenarios, the anaerobic, aerobic, and strength demands are so specific and the time to improve all training demands in the units is limited. We propose a new training periodization for the military population based on the latest research into the psychophysiological response of soldiers in actual theaters of operations (actual military missions) and actual civilian models of training and periodization to develop a specific, easy, and reliable periodization model for actual tactical athletes. This training intervention was developed in order to improve operational training according to the demands of actual theaters of operations, based on recent research in military and civilian populations. We tried to conduct a proposal that is easy to apply, with minimal use of material different to what could be found in a military base and that could be implemented in a short period of time.

The Relationship Between Functional Motor Competence and Performance on the Army Combat Fitness Test in Army Reserve Officer Training Corps Cadets

INTRODUCTION

The development of functional motor competence (FMC; i.e., neuromuscular coordination and control required to meet a wide range of movement goals) is critical to long-term development of health- and performance-related physical capacities (e.g., muscular strength and power, muscular endurance, and aerobic endurance). Secular decline in FMC among U.S. children and adolescents presents current and future challenges for recruiting prospective military personnel to successfully perform the physical demands of military duty. The purpose of the current study was to examine the relationship between FMC and physical military readiness (PMR) in a group of Cadets enrolled in an Army Reserve Officer Training Corps program.

MATERIALS AND METHODS

Ninety Army Reserve Officer Training Corps Cadets from a southeastern university and a military college in the southeast (females = 22; Mage = 19.5 ± 2.5) volunteered for participation in the study. Cadets performed a battery of eight FMC assessments consisting of locomotor, object projection, and functional coordination tasks. To assess PMR, Cadets performed the Army Combat Fitness Test (ACFT).Values from all FMC assessments were standardized based on the sample and summed to create a composite FMC score. ACFT scores were assigned to Cadets based upon ACFT scoring standards. We used Pearson correlations to assess the relationships between individual FMC assessment raw scores, FMC composite scores, and total ACFT points. We also evaluated the potential impact of FMC on ACFT in the entire sample and within each gender subgroup using hierarchical linear regression. Finally, we implemented a 3 × 2 chi-squared analysis to evaluate the predictive utility of FMC level on pass/fail results on the ACFT by categorizing Cadets' composite FMC score into high (≥75th percentile) moderate (≥25th percentile and <75th percentile), and low (<25th percentile) based on the percentile ranks within the sample. ACFT pass/fail results were determined using ACFT standards, requiring a minimum of 60 points on each the ACFT subtests.

RESULTS

FMC composite scores correlated strongly with total ACFT performance (r = 0.762) with individual FMC tests demonstrating weak-to-strong relationships ACFT performance (r = 0.200-0.769). FMC uniquely accounted for 15% (95% CI: -0.07 to 0.36) of the variance in ACFT scores in females (R2 = 0.516, F2,19 = 10.11, P < 0.001) and 26% (95% CI: 0.09-0.43) in males (R2 = 0.385, F2,65 = 20.37, P < 0.001), respectively, above and beyond the impact of age. The 3 × 2 chi-squared analysis demonstrated 74% of those with low, 28% with moderate, and 17% with high FMC failed the ACFT (χ2 [1, N = 90] = 27.717, V = 0.555, P < 0.001).

CONCLUSION

FMC composite scores are strongly correlated with ACFT scores, and low levels of FMC were a strong predictor of ACFT failure. These data support the hypothesis that the development of sufficient FMC in childhood and adolescence may be a critical antecedent for PMR. Efforts to improve FMC in children and adolescents may increase PMR of future military recruits.

Editorial: Military human performance optimization: Contemporary issues for sustained and improved readiness

This issue of the European Journal of Sport Science includes 8 invited state-of-the-science narrative reviews by well-established researchers in the area of military performance focused on (a) physical training; (b) musculoskeletal injury; (c) adaptive bone formation and stress fracture prevention; (d) sex differences in responses to military stress; (e) load monitoring in military settings; (g) circulating biomarkers related to resilience during military stress; (H) military nutrition research; and (I) development of military exoskeletons. Important historical, current and future scientific and research information and guidance within the context of sustained and improved military physical performance and readiness are provided. Conclusions and recommendations for protecting Soldier health and resiliency include: (1) combined physical training emphasizing higher intensity but lower volume; (2) musculoskeletal injury risk factors most supported from the literature include: female sex, prior injury and low fitness; (3) adequate sleep, vitamin D, calcium, and energy availability are all critical for creating a resilient skeleton protecting against stress fractures; (4) differences between men and women when exposed to military stress include cardiovascular strain, fat oxidation, and psychological health risk; (5) biomarkers (cortisol, epi/norepi, ILs 4, 6, 10, 18 and TNF-alpha, IGF-I, testosterone, DHEA) offer insight for internal stress; (6) monitoring physiological training load should include consideration for multiple inputs, rather than a single measure; (7) nutrition optimization includes determining operational requirements, nutritional practices and nutrient delivery strategies; and (8) future generation exoskeletons will achieve a better balance of intended movement based on individual user and interactions with internal and external constraints.

Applying Force Plate Technology to Inform Human Performance Programming in Tactical Populations

Force plate assessments, such as countermovement jumps and isometric mid-thigh pulls, examine performances (e.g., jump height, force, power) and movement strategies (e.g., asymmetries, durations), and are best suited to characterize and monitor physical capabilities, not predict injuries. To begin applying force plate technologies, users must first; (1) develop a data management plan to visualize and capture data over time; (2) select appropriate force plates for their scenario; (3) design appropriate testing protocols to ensure valid and reliable data. Force plate assessments may be added to existing testing, serve as separate testing batteries for annual profile testing to compare individuals and understand initial physical capabilities, or for more frequent testing (i.e., monthly or weekly) to monitor training-related adaptations or neuromuscular fatigue. Although these assessments inform evidence-based program designs, human performance practitioners must understand the considerations for conducting appropriate force plate testing, as well as proper visualizations and management of force plate data. Thus, the aim of this review is to provide evidence-based practices for utilizing force plates in tactical populations (e.g., military, firefighters, police). This includes best practices to implement testing for performance profiling, training adaptations, and monitoring neuromuscular fatigue and force asymmetries. Of note, due to the large amount of force-time metrics to choose from, this article provides general examples of important metrics to monitor and training recommendations based on changes to these force-time metrics, followed by specific examples in three case studies.

Altered Physical Performance Following Advanced Special Operations Tactical Training

ABSTRACT

Winters, JD, Heebner, NR, Johnson, AK, Poploski, KM, Royer, SD, Nagai, T, Randall, CA, Abt, JP, and Lephart, SM. Altered physical performance following advanced special operations tactical training. J Strength Cond Res 35(7): 1809-1816, 2021-The purpose of this study was to determine how the unique challenges of specific military tactical training phases influence overall physical performance characteristics. Broad jump, 5-10-5, 300-yd shuttle, percent body fat (%BF), anaerobic power (AP) and anaerobic capacity (AC), maximal oxygen uptake (V̇o2max), isokinetic knee extension/flexion strength, shoulder internal/external rotation strength, and trunk extension/flexion strength were collected on 73 United States Marine Corps Forces Special Operations Command (MARSOC) students (age: 27.4 ± 3.8 years, height: 178.7 ± 6.6 cm, and body mass: 85.8 ± 9.4 kg) at the beginning of (P1), in between (P2), and at the completion of 2 distinct tactical training phases (P3). Linear mixed models were used to analyze within-subject performance changes over the 3 time points, and post hoc Bonferroni pairwise comparisons analyzed performance changes between each testing time point. There were significant changes in broad jump (p < 0.0001), 5-10-5 agility time (p < 0.001), %BF (p = 0.011), AP (p < 0.0001), V̇o2max (p = 0.001), and both right and left shoulder internal rotation strength (p = 0.004 and p = 0.015, respectively) between P1 and P2. There were also significant changes in 300-yd shuttle run time (p = 0.001), AP (p < 0.0001), AC (p < 0.0001), left knee extension strength (p = 0.006), trunk flexion strength (p < 0.0001), and left shoulder external rotation strength (0.027) between P2 and P3. Identifying the effect that specific tactical training phases may have on physical performance will allow for the development of effective phase-specific evidence-based human performance programs, reducing performance deficits and thereby reducing the risk of injury.

Physical training considerations for optimizing performance in essential military tasks

Physically demanding essential military tasks include load carriage, manual material handling and casualty evacuation. This narrative review characterizes the main physical attributes related to performance of these occupational tasks and reviews physical training intervention studies in military settings to improve performance in these military tasks. Load carriage performance requires both aerobic and neuromuscular fitness with greater emphasis on maximal strength and absolute maximal oxygen uptake, especially when carrying heavier loads. In manual material handling, maximal strength and power are strongly associated with discrete lifting, while muscular strength, muscular endurance and aerobic fitness are also associated with repetitive lifting performance. Maximal strength including grip strength, muscular endurance, absolute maximal oxygen uptake and anaerobic capacity are associated with casualty evacuation performance. The results of the present review particularly emphasize the role of muscular fitness in successful performance of the reviewed military occupational tasks. Training intervention studies indicate that load carriage performance can be effectively improved by combining strength, aerobic and specific load carriage training. Improvement in maximal lifting capacity can be achieved by strength training or combined strength and aerobic training, while strength and aerobic training alone, or their combination are effective in improving repetitive lifting, and carry tasks. Only a few studies are available for casualty evacuation and the results are inconclusive but may indicate benefits of strength or combined training. Moreover, emphasis on lower volume but higher intensity in combined training may be a feasible and effective mode to improve military occupational performance in recruits and active-duty soldiers.

Training Strategies Maintain Performance Characteristics in Marines Selected for Marine Forces Special Operations Individualized Training Course

INTRODUCTION

Marines must complete an intensive Assessment and Selection (A&S) course before becoming a U.S. Marine Forces Special Operations Command (MARSOC) Raider. Following selection, marines are given training recommendations designed to maintain performance characteristics deemed relevant to successfully complete a rigorous 9-month Individualized Training Course (ITC). However, training strategies are individually implemented by the marine, and the time between the two courses is highly irregular, ranging between 2 months and 24 months based on operational factors related to military occupational specialty (MOS). The purpose of this study was to evaluate changes in performance between the completion of A&S and the start of ITC and to examine if the duration between courses and previous MOS influenced changes in performance.

MATERIALS AND METHODS

Body fat percentage (BF%), anaerobic power (AP), anaerobic capacity (AC), aerobic capacity (VO2max), knee flexion (KF), knee extension (KE), trunk extension (TE), and trunk flexion (TF) isokinetic strength were collected on 38 marines (age: 25.1 ± 2.7 years, height: 1.77 ± 0.05 m, mass: 83.2 ± 7.7 kg, Post-A&S to ITC start: 204.1 ± 68.4 days) following A&S and directly before ITC.

RESULTS

Pre-ITC students had significantly greater mass (P = .002), BF% (P = .000), and AP (P = .039). There were no significant changes in AC (P = .170), VO2max (P = .259), KF (P = .400), KE (P = .320), TE (P = .178), and TF (P = .643). There was no significant relationship between performance outcomes and time between courses and previous MOS.

CONCLUSION

Current training strategies appear effective at addressing performance deficits that occur as a result of A&S, while maintaining high levels of KF, KE, TE, TF, AC, and VO2max. However, pre-ITC students still exhibited AP deficits compared to active marine raiders, so forthcoming programming may benefit from an increased emphasis on AP. Assessment of additional selectees at these timepoints, as well as students before A&S may provide valuable information to MARSOC human performance specialists to develop programing, ultimately leading to a higher ITC graduation rate, increased force readiness, and decreased financial burden forcewide.

Effects of an Experimental vs. Traditional Military Training Program on 2-Mile Run Performance During the Army Physical Fitness Test

Stone, BL, Heishman, AD, and Campbell, JA. The effects of an experimental vs. traditional military training program on 2-mile run performance during the army physical fitness test. J Strength Cond Res 34(12): 3431-3438, 2020-The purpose of this study was to compare the effects of an experimental vs. traditional military run training on 2-mile run ability in the Army Reserve Officers' Training Corps cadets. Fifty college-aged cadets were randomly placed into 2 groups and trained for 4 weeks with either an experimental running program (EXP, n = 22) comprised rating of perceived exertion (RPE) intensity-specific, energy system-based intervals or with traditional military running program (TRA, n = 28) using a crossover study design. A 2-mile run assessment was performed just before the start, at the end of the first 4 weeks, and again after the second 4 weeks of training after crossover. The EXP program significantly decreased 2-mile run times (961.3 ± 155.8 seconds to 943.4 ± 140.2 seconds, p = 0.012, baseline to post 1), whereas the TRA group experienced a significant increase in run times (901.0 ± 79.2 vs. 913.9 ± 82.9 seconds) over the same training period. There was a moderate effect size (d = 0.61, p = 0.07) for the experimental run program to "reverse" the adverse effects of the traditional program within the 4-week training period (post 1 to post 2) after treatment crossover. Thus, for short-term training of military personnel, RPE intensity-specific running program comprising aerobic and anaerobic system development can enhance 2-mile run performance superior to a traditional program while reducing training volume (60 minutes per session vs. 43.2 minutes per session, respectively). Future research should extend the training period to determine efficacy of this training approach for long-term improvement of aerobic capacity and possible reduction of musculoskeletal injury.

INFLUENCE OF LIMB DOMINANCE AND SHOULDER INJURY ON STRENGTH AND EXPLOSIVE FORCE IN US MARINES

Background

The specialized roles of many military personnel require specific skills and high physical demands, placing unique stresses on the shoulders and increasing risk of injury. As normal dominant/nondominant shoulder asymmetries have been established in military personnel, bilateral strength comparisons must be understood in context of daily physical demands to monitor patients' progress or readiness to return to duty.

Purpose

This study aims to assess bilateral differences in strength and explosive force in United States Marines with a history of dominant or nondominant shoulder pathology.

Study Design

Cross-Sectional.

Methods

A total of 52 full-duty, male US Marines with a shoulder injury within the prior year participated. Bilateral isokinetic shoulder internal (IR) and external (ER) rotation strength, and peak force (Peak Force) and average rate of force production (Avg Rate) during an explosive push-up were collected. Dominant versus nondominant side data were independently examined within each group (DOM: dominant injury, NOND: nondominant injury). Comparison between DOM and NOND, as well as previously published CON (no history of shoulder injury) was also completed.

Results

NOND (n = 26) demonstrated significantly less IR (p < 0.001) and ER (p = 0.003) strength and Peak Force (p = 0.001) and Avg Rate (p = 0.047) on the injured side, while DOM (n = 26) demonstrated no bilateral differences in strength or push-up performance. Comparison between the three groups showed that NOND demonstrated significantly less ER strength than CON (p = 0.022).

Conclusions

Military personnel demonstrate asymmetric strength patterns likely due to increased demand of the dominant shoulder. US Marines with a history of injury to the nondominant shoulder performed differently than those with a dominant side injury, presenting with both strength and push-up asymmetries. They also demonstrated significant ER strength deficits compared to CON. Common clinical practice and previous literature often compare injured and uninjured limbs or injured individuals to healthy controls, but further distinction of dominant or nondominant side may provide more accurate information needed to develop targeted treatment strategies.

Clinical Relevance

Recognizing unique occupational demands and how patients may present differently with dominant versus nondominant side shoulder injuries are important considerations for ensuring accurate assessment and effective individualized rehabilitation.

Level of Evidence

3.

Effects of Task-Specific and Strength Training on Simulated Military Task Performance in Soldiers

A soldier’s occupational physical task requirements are diverse and varied. However, the type of physical training that most effectively improves soldiers’ occupational task requirements has not been studied previously. The purpose of this study was to determine the important strength characteristics for soldiers during a repeated simulated military task course, and the type of training that may be effective to improve these abilities during a specialized military training period. Forty-two (n = 42) soldiers participated in the study. They were divided into three training groups; a soldier task-specific training group (TSG, n = 17), a strength training group (STG, n = 15), and a control group (CON, n = 10). Participants were measured before (PRE), middle (MID) and after (POST) the 12-week training intervention for strength performance and simulated military task test. Simulated military task performance improved significantly in TSG and STG between the PRE and MID measurements (from 9.4 to 15.7%). TSG and STG improved in various spilt times, especially in strength tasks; casualty drag (from 8.3 to 13.6%) and kettlebell carry (from 13.2 to 22.4%) between the PRE and MID measurements. The present study showed that both the training of TSG and STG were more effective than the training of CON (control group) in terms of improving the performance in the repeated simulated military task course. The present study showed that training of TSG was as effective as STG to improve repeated simulated military task course time. Therefore, an optimal training combination should include high-intensity simulated military task field training and strength training programmed with consideration of the military training phase and environmental possibilities.

Changes in strength and power performance and serum hormone concentrations during 12 weeks of task-specific or strength training in conscripts

The purpose of this study was to investigate the effects of two different training programs on strength and power performance and serum hormone concentrations. A total of 104 male soldiers volunteered and took part in the 12‐week training period with baseline, mid‐, and post‐measurements of body composition, muscle strength, lower and upper body power, and blood samples to determine serum hormone concentrations. The mean (±SD) age of subjects was 20 ± 1 years, height 180 ± 6 cm and body mass 72.4 ± 8.8 kg. The subjects were divided into three different training groups: soldier task‐specific training (TS), strength training (ST), and control (CON). Each group had a total of 18 training sessions during the 12‐week study. In the muscle strength tests, most improvements could be observed in the TS and ST groups, especially, during the first weeks of the training period. Maximal isometric leg extension force increased significantly by 7.9 ± 12.2% (p < .05) in the TS and 7.1 ± 12.6% (p < .05) in the ST groups between the PRE and MID, as well as between the PRE and POST measurements by 8.1 ± 12.4% (p < .05) in TS and 12.3 ± 15.3% (p < .01) in ST. Serum TES concentration increased significantly in TS between the PRE and MID (16.8 ± 33.9%) and PRE and POST (11.2 ± 16.7%) measurements. Serum COR concentrations decreased in TS between the MID and POST (−7.8 ± 10.9%) and PRE and POST (−11.0 ± 14.3%) measurements. Although the differences observed were rather minor in magnitude, training in the TS and ST groups led to greater improvements in muscle strength and power performance compared to the training in the CON group. The development of strength and/or power of the lower and upper body was greater in the TS and ST groups, which is crucial for warfighter's performance. Therefore, it is important to have a structured resistance‐training program during military training to optimize the strength, power, and military‐specific performance.

Differences in Training Adaptations of Endurance Performance during Combined Strength and Endurance Training in a 6-Month Crisis Management Operation

Decreases in aerobic fitness during military operations have been observed in several studies. Thus, differences in training adaptations during a 6-month crisis-management operation were compared by using the change in endurance performance as the outcome measure. Sixty-six male soldiers volunteered for the study, consisting of pre-post assessments of blood biomarkers, body composition, physical performance, and the military simulation test (MST) performance. Physical training volume was self-reported. After the follow-up, the data were divided based on individual changes in endurance performance. Endurance performance was improved in the high-responder group (HiR, n = 25) and maintained or decreased in the low-responder group (LoR n = 24). During the operation, the LoR group decreased while the HiR group increased their endurance training frequency from the pre-deployment level (Δ 28 ± 57% vs. -40 ± 62%, p = 0.004). Fat mass decreased (-7.6 ± 11.7% vs. 14.2 ± 20.4%, p < 0.001), and 1-min push-up (27.7 ± 21.9% vs. 11.7 ± 26.1%, p = 0.004) and MST performance improved (-13.6 ± 6.8% vs. -7.5 ± 6.5%, p = 0.006) more in the HiR group. No differences were observed in the changes of other physical performance test results or analyzed biomarkers. In conclusion, soldiers who were initially leaner and fitter in terms of lower body strength and power were more likely to decrease their aerobic fitness during the operation.

Effects of baseline fitness and BMI levels on changes in physical fitness during military service

OBJECTIVES

The purpose of the present study was to investigate how aerobic fitness, muscle fitness and body mass index (BMI) change in relation to their baseline levels during 6-12 months of military service.

DESIGN

Retrospective longitudinal follow-up study.

METHODS

The study group consisted of 249279 healthy young male conscripts (age 19.1±0.4 yrs.) who completed their military service between the years 2005-2015. Anthropometrics (body mass, height, BMI), aerobic fitness (12-min running test) and muscle fitness (sit-ups, push-ups, standing long jump) were measured.

RESULTS

A 12-min running test improved by 5% (107±292m), standing long jump 1% (2.1±16.2cm), 1-min sit-ups 19% (4±8 repetitions/min) and 1-min push-ups 33% (5±10 repetitions/min) (p<0.001 for all). Baseline fitness and baseline BMI levels were inversely associated with their changes (r=-0.37 to -0.47, p<0.001). Performance improved in conscripts in the lowest two baseline fitness quartiles in all tests, while it decreased in conscripts in the highest fitness quartiles. In addition, in conscripts who were obese at baseline, body mass decreased on average by 4.9±7.0kg (p<0.001).

CONCLUSIONS

On average, the physical fitness of conscripts improved during their compulsory military service. In particular, conscripts with a lower baseline fitness level or higher BMI showed the largest improvements, which may be significant findings from both a military readiness and national health perspective. However, the decline in physical performance of high-fit conscripts highlights the importance of individualization of physical training and military training load during military service.

Validity and reliability evidence of a point of care assessment of salivary cortisol and α-amylase: a pre-registered study

PURPOSE

The iPro Cube is a small portable point-of-care device designed to analyse salivary markers of stress in a user-friendly manner (e.g., fast, convenient). Our aim was to test the reliability and validity of the iPro Cube to measure salivary cortisol and α-amylase as compared to the common laboratory standard method (ELISA immunoassay) prior to and after moderate intensity exercise.

METHODS

The study was a repeated measures, pre-registered design, and statistical framework that incorporated prior knowledge directly into the estimation process. Twenty-nine individuals (age = 27.4 ± 6.6 y; body-mass = 70.8 ± 11.3 kg; height = 1.74 ± 0.92 m; 18 males) completed a single PWC75%HRmax, with repeated measures of salivary cortisol and -amylase pre, immediately post, and 30 min post-exercise.

RESULTS

Correlation between the iPro Cube and laboratory-based assessments of salivary cortisol was moderate-to-large (0.53 > r < 0.81) across all three testing points. In contrast, correlation between the iPro Cube and laboratory-based assessments of -amylase was small-to-moderate (0.25 > r < 0.46). We found a large correlation between duplicate samples of iPro Cube cortisol assessment (0.75 > r < 0.82), and a moderate-to-large correlation for -amylase (0.51> r < 0.77).

CONCLUSIONS

The iPro Cube is capable of taking measures of salivary cortisol that are moderately correlated to values obtained via ELISA immunoassay, however the unit underestimates salivary cortisol and overestimates salivary -amylase at rest and post-moderate intensity exercise. It is recommended that researchers continue using standard laboratory techniques to assess these salivary stress markers.

Relationship of Anthropometric Measures on Female Trainees' and Active Duty Soldiers' Performance of Common Soldiering Tasks

INTRODUCTION

This study compared the relationship between height (HT), body mass (BM), and body mass index (BMI) of female trainees and active duty female soldiers and their performance on simulated common soldiering tasks (CSTs) with high physical demands.

METHODS

Female trainees (n = 133) and soldiers (n = 229) completed the following CSTs: sandbag carry, move under fire, casualty drag, casualty evacuation, and road march. Quartiles were created among HT, BM, and BMI by which task performance was compared using ANOVAs with Tukey post hoc comparisons.

RESULTS

For both trainees and soldiers, HT, BM, and BMI were positively associated with improved road march, casualty drag, casualty evacuation, and sandbag carry performance. On the move under fire task, only soldier HT was positively associated with improved performance.

CONCLUSION

Female trainees and soldiers who are taller and heavier with a higher BMI may demonstrate better performance on CSTs required of all soldiers. In addition to task-specific training, performance of CSTs may be enhanced in tasks requiring strength and power by recruiting and retaining taller and heavier females with a higher BMIs. Allowances should be considered for soldiers and trainees who can successfully perform soldiering tasks with high physical demands despite less desirable anthropometric measurements.

Physical Employment Standards for UK Royal Navy Personnel: A Survey of Tasks That Require Muscle Strength and Endurance

INTRODUCTION

Physical Employment Standards (PES) safeguard the requirement to create a suitable job-person fit in military occupations, and in doing so mitigate some operational and musculoskeletal injury risk. The primary purpose of this research was to identify critical - physically demanding tasks performed by UK Royal Navy (RN) seafarers to inform the development of a muscle strength and endurance-based PES. A secondary purpose was to explore possible sex and age-based differences in subjective ratings of occupational task physical demand.

MATERIALS AND METHODS

In accordance with the Ministry of Defence Research Ethics Committee, 515 Naval personnel (443 males, 72 females; aged 30.2 ± 7.3 years) completed an anonymous survey that rated the physical demand (from no to very high), criticality (from not to critically important), and frequency (from seldom to several times per day) of 25 common sea-going tasks on a one to five scale. An a priori criteria was applied to down-select a shortlist of the most critical and physically demanding tasks (i.e., median task criticality and task physical demand scores of ≥4, and ≥3, respectively). A Mann-Whitney and Kruskal-Wallis test explored sex and age-based differences in subjective physical demand ratings.

RESULTS

Ten (out of 25) tasks met the critical - physical demand criteria, which included the four task categories of fire fighting, damage control, casualty handling, and basic movement/transit tasks. Casualty handling emerged as the single most physically demanding task category performed by seafarers, which was rated to have "high" physical demand (4 on the 1 to 5 scale). Sex and age-based differences in subjective ratings of task physical demand were equivocal, with females rating 3 (out of the 25 tasks), and 40-51 year olds rating 4 (out of 25 tasks) to have a higher physical demand than males and 19-29 year olds, respectively.

CONCLUSION

Ten criterion tasks were identified and should undergo a further job analysis to inform the development of strength-based PES for the RN.

Influence of Vitamin D Supplementation by Sunlight or Oral D3 on Exercise Performance

Purpose

To determine the relationship between vitamin D status and exercise performance in a large, prospective cohort study of young men and women across seasons (study 1). Then, in a randomized, placebo-controlled trial, to investigate the effects on exercise performance of achieving vitamin D sufficiency (serum 25(OH)D ≥ 50 nmol·L⁻¹) by a unique comparison of safe, simulated-sunlight and oral vitamin D₃ supplementation in wintertime (study 2).

Methods

In study 1, we determined 25(OH)D relationship with exercise performance in 967 military recruits. In study 2, 137 men received either placebo, simulated sunlight (1.3× standard erythemal dose in T-shirt and shorts, three times per week for 4 wk and then once per week for 8 wk) or oral vitamin D₃ (1000 IU·d⁻¹ for 4 wk and then 400 IU·d⁻¹ for 8 wk). We measured serum 25(OH)D by high-pressure liquid chromatography tandem mass spectrometry and endurance, strength and power by 1.5-mile run, maximum dynamic lift and vertical jump, respectively.

Results

In study 1, only 9% of men and 36% of women were vitamin D sufficient during wintertime. After controlling for body composition, smoking, and season, 25(OH)D was positively associated with endurance performance (P ≤ 0.01, ΔR² = 0.03–0.06, small f² effect sizes): 1.5-mile run time was ~half a second faster for every 1 nmol·L⁻¹ increase in 25(OH)D. No significant effects on strength or power emerged (P > 0.05). In study 2, safe simulated sunlight and oral vitamin D₃ supplementation were similarly effective in achieving vitamin D sufficiency in almost all (97%); however, this did not improve exercise performance (P > 0.05).

Conclusions

Vitamin D status was associated with endurance performance but not strength or power in a prospective cohort study. Achieving vitamin D sufficiency via safe, simulated summer sunlight, or oral vitamin D₃ supplementation did not improve exercise performance in a randomized-controlled trial.

Effects of 10 weeks of military training on neuromuscular function in non-overreached and overreached conscripts

The purpose of the study was to examine how military training influences neuromuscular function in non-overreached and overreached conscripts. A total of 24 male conscripts participated in the study (8 weeks basic training + 2 weeks specialized training). All measurements were conducted during weeks 1, 5, 8 and 10. After the training period, non-overreached (NOR, n = 16) and overreached (OR, n = 8) groups were compared. Isometric maximal forces (bench press, elbow flexion and knee extension), single twitch (plantar flexors), H-reflex, M-wave (Hmax/Mmax) and V-wave (V/Mmax) (soleus) were measured. In knee extension, force production increased in NOR by 22.5 ± 20.5% (p < 0.01) between weeks 1 and 8, which was not observed in OR (-1.1 ± 18.2%, p > 0.05). In OR, plantarflexion twitch contraction time increased between weeks 5 and 10 by 82.2 ± 34.4% (p < 0.01), which was not observed in NOR. No changes were observed in the H-reflex and V-wave responses in either of the groups. In conclusion, short term overreaching can also reduce the performance of the neuromuscular system, however, it seems to be more muscle than neural based. To avoid overreaching, more individualized periodization should be used during basic training. To enhance neuromuscular performance, maximal and explosive strength training should also be added into the basic training program.

Relationship of Strength and Conditioning Metrics to Success on the Army Ranger Physical Assessment Test

Barringer, ND, McKinnon, CJ, O'Brien, NC, and Kardouni, JR. Relationship of strength and conditioning metrics to success on the army ranger physical assessment test. J Strength Cond Res 33(4): 958-964, 2019-The purpose of our study was to compare standard strength and conditioning assessments in the Ranger Athlete Warrior (RAW) assessments to a tactical assessment of the Ranger Physical Assessment Test (RPAT) to determine what influence, if any, that they may have on the RPAT outcome. We analyzed RAW and RPAT data on 1,141 soldiers attempting the Ranger Assessment and Selection Program I (RASP I) for entrance into the 75th Ranger Regiment as part of their routine program data collection from July 2014 to July 2017. We found better performance in the broad jump, pull-ups, and average 300-yard shuttle time was associated with improved odds of passing the RPAT. For every increasing 2.54 centimeters in broad jump, the odds of passing the RPAT increased by 4% (OR = 1.04, 95% CI [1.01-1.07]). Each additional pull-up was associated with 6% better odds (OR = 1.06, 95% CI [1.01-1.12]) of passing the RPAT, and every second faster in the 300-yard shuttle was associated with 9% better odds of passing the RPAT (OR = 1.09, 95% CI [1.03-1.14]). The results of this study indicate that lower-body power, pulling strength, and anaerobic conditioning seemed to have the greatest influence on RPAT success. Our current results provide guidance to Strength Coaches or TSAC-Fs preparing tactical athletes for this specific or similar tactical assessment as better performance was found for tactical athletes with greater lower-body power, pulling strength, and anaerobic endurance.

Associations of Physical Fitness and Body Composition Characteristics With Simulated Military Task Performance

Pihlainen, K, Santtila, M, Häkkinen, K, and Kyröläinen, H. Associations of physical fitness and body composition characteristics with simulated military task performance. J Strength Cond Res 32(4): 1089-1098, 2018-The purpose of this study was to evaluate the associations of physical fitness and body composition characteristics with anaerobic endurance performance, tested in the combat load using the occupationally relevant military simulation test (MST). Eighty-one male soldiers, deployed to a crisis management operation in the Middle East, volunteered for the study and participated in a test battery consisting measurements of muscle strength, body composition characteristics, endurance capacity, and MST. A Spearman correlational analysis revealed that the strongest variable, correlated with MST time, was the countermovement jump performed with the combat load (CMJ2) (rs = -0.66, p < 0.001). Among the individual body composition variables, the MST time had the strongest relationship with fat percentage (rs = 0.53, p < 0.001) and skeletal muscle mass (SMM) (rs = -0.47, p < 0.001). The use of the dead mass ratio, which was calculated dividing body mass by fat mass accompanied with the weight of the combat load, increased body composition-based associations significantly, and this variable turned out to be the best single predictor for the MST performance (rs = -0.67, p < 0.001). Significant predictors of the MST time in the stepwise multivariate regression analysis included CMJ2, 3000 m, SMM, and push-ups. Together, these variables explained 66% ((Equation is included in full-text article.), model p < 0.001) of the variance in the MST time. In conclusion, the novel MST is a promising military specific assessment method of muscle power of the lower extremities and endurance capacity, which are crucial performance components in anaerobic combat situations.

Significantly Increased Odds of Reporting Previous Shoulder Injuries in Female Marines Based on Larger Magnitude Shoulder Rotator Bilateral Strength Differences

Background:

Musculoskeletal injuries to the extremities are a primary concern for the United States (US) military. One possible injury risk factor in this population is side-to-side strength imbalance.

Purpose:

To examine the odds of reporting a previous shoulder injury in US Marine Corps Ground Combat Element Integrated Task Force volunteers based on side-to-side strength differences in isokinetic shoulder strength.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Male (n = 219) and female (n = 91) Marines were included in this analysis. Peak torque values from 5 shoulder internal/external rotation repetitions were averaged and normalized to body weight. The difference in side-to-side strength measurements was calculated as the absolute value of the limb difference divided by the mean peak torque of the dominant limb. Participants were placed into groups based on the magnitude of these differences: <10%, 10% to 20%, and >20%. Odds ratios (ORs) and 95% CIs were calculated.

Results:

When separated by sex, 13.2% of men reported an injury, while 5.5% of women reported an injury. Female Marines with >20% internal rotation side-to-side strength differences demonstrated increased odds of reporting a previous shoulder injury compared with female Marines with <10% strength differences (OR, 15.4; 95% CI, 1.4-167.2; P = .03 ) and female Marines with 10% to 20% strength differences (OR, 13.9; 95% CI, 1.3-151.2; P = .04). No significant ORs were demonstrated in male Marines.

Conclusion:

Marines with larger magnitude internal rotation strength differences demonstrated increased odds of reporting a previous shoulder injury compared with those with lesser magnitude differences. Additionally, female sex appears to drastically affect the increased odds of reporting shoulder injuries (OR, 13.9-15.4) with larger magnitude differences (ie, >20%) compared with those with lesser magnitude differences (ie, <10% and 10%-20%). The retrospective cohort design of this study cannot delineate cause and effect but establishes a relationship between female Marines and greater odds of larger magnitude strength differences after returning from an injury.

Greater ankle strength, anaerobic and aerobic capacity, and agility predict Ground Combat Military Occupational School graduation in female Marines

Women can serve in all military occupational specialties (MOS); however, musculoskeletal and physiological characteristics that predict successful completion of ground combat MOS schools by female Marines are unknown.

OBJECTIVES

To determine which demographic, musculoskeletal, and physiological characteristics predict graduation from infantry and vehicle ground combat MOS schools in female Marines.

DESIGN

Prospective cohort study.

METHODS

Prior to MOS school, the following were assessed in 62 female Marines (22.0±3.0yrs, 163.9±5.8cm, 63.4±7.2kg): isokinetic shoulder, trunk, and knee and isometric ankle strength; body composition; anaerobic power (AP)/capacity (AC); maximal oxygen uptake (VO₂max); and field-based fitness tests (broad jump, medicine ball throw, pro-agility). Both absolute and normalized (%body mass: %BM) values were utilized for strength, AP, AC, and VO₂max. Select tests from each Marine's most recent Physical Fitness Test (PFT: abdominal crunches, 3-mile run time) and Combat Fitness Test (CFT: Maneuver Under Fire, Movement to Contact) were recorded. Participants were classified as graduated (N=46) or did not graduate (N=16). Simple logistic regression was performed to determine predictors of MOS school graduation. Statistical significance was set a priori at α=0.05.

RESULTS

Absolute and normalized ankle inversion and eversion strength, normalized anaerobic capacity, absolute and normalized VO₂max, right pro-agility, and PFT 3-mile run time significantly predicted MOS school graduation (p<0.05).

CONCLUSIONS

Greater ankle strength, better agility, and greater anaerobic and aerobic capacity are important for successful completion of ground combat MOS school in female Marines. Prior to entering ground combat MOS school, it is recommended that female Marines should train to optimize these mobility-centric characteristics.