Bilateral Quadriceps Strength Asymmetry Is Associated With Previous Knee Injury in Military Special Tactics Operators.

Eagle, SR, Keenan, KA, Connaboy, C, Wohleber, M, Simonson, A, and Nindl, BC. Bilateral quadriceps strength asymmetry is associated with previous knee injury in military special tactics operators. J Strength Cond Res 33(1): 89-94, 2019-Bilateral strength asymmetries have been related to lower-limb injury in athletes. Given that military populations often participate in recreational sport, in addition to a physically demanding workload, bilateral strength asymmetries may be related to injury in military populations. The purpose of this study was to determine whether isokinetic strength differs between Operators with/without self-reported knee injury (KI), and to examine the odds of displaying a lower-extremity strength asymmetry based on previous KI history. Operators (n = 150) self-reported injury history and performed isokinetic knee strength testing. Cohorts were separated by those who reported/not reported KI. Mean isokinetic knee strength and odds ratios, with subjects' KI history compared with strength differences: <10, 10-20, and >20%, were calculated. Operators who reported KI demonstrated larger bilateral knee extension (KE) strength differences compared with those who did not report an injury (injured: 13.5 ± 12.9% vs. noninjured: 8.1 ± 5.9%, p = 0.01). Operators with <10 or 10-20% KE strength difference had 76-77% reduced odds of previous KI, compared to those with >20% strength difference (p < 0.05). Operators with previous KI demonstrated bilateral differences in KE strength. Those with <10 or 10-20% strength differences had reduced odds of reporting previous KI. Strength and conditioning professionals should consider unilateral, targeted exercises in reducing bilateral asymmetry to rectify more balanced strength between limbs. Targeted exercise programs may improve bilateral strength differences and limit reinjury risk.

The Relationship of Core Strength and Activation and Performance on Three Functional Movement Screens.

Johnson, CD, Whitehead, PN, Pletcher, ER, Faherty, MS, Lovalekar, MT, Eagle, SR, and Keenan, KA. The relationship of core strength and activation and performance on three functional movement screens. J Strength Cond Res 32(4): 1166-1173, 2018-Current measures of core stability used by clinicians and researchers suffer from several shortcomings. Three functional movement screens appear, at face-value, to be dependent on the ability to activate and control core musculature. These 3 screens may present a viable alternative to current measures of core stability. Thirty-nine subjects completed a deep squat, trunk stability push-up, and rotary stability screen. Scores on the 3 screens were summed to calculate a composite score (COMP). During the screens, muscle activity was collected to determine the length of time that the bilateral erector spinae, rectus abdominis, external oblique, and gluteus medius muscles were active. Strength was assessed for core muscles (trunk flexion and extension, trunk rotation, and hip abduction and adduction) and accessory muscles (knee flexion and extension and pectoralis major). Two ordinal logistic regression equations were calculated with COMP as the outcome variable, and: (a) core strength and accessory strength, (b) only core strength. The first model was significant in predicting COMP (p = 0.004) (Pearson's Chi-Square = 149.132, p = 0.435; Nagelkerke's R-Squared = 0.369). The second model was significant in predicting COMP (p = 0.001) (Pearson's Chi-Square = 148.837, p = 0.488; Nagelkerke's R-Squared = 0.362). The core muscles were found to be active for most screens, with percentages of "time active" for each muscle ranging from 54-86%. In conclusion, performance on the 3 screens is predicted by core strength, even when accounting for "accessory" strength variables. Furthermore, it seems the screens elicit wide-ranging activation of core muscles. Although more investigation is needed, these screens, collectively, seem to be a good assessment of core strength.

Throwing Shoulder Adaptations Are Not Related to Shoulder Injury or Pain: A Preliminary Report.

BACKGROUND: Overhead throwing in baseball and softball athletes induces shoulder adaptations theorized to increase risk of shoulder musculoskeletal injury (MSI) and/or pain due to range of motion (ROM) deficits. HYPOTHESIS: Shoulder ROM adaptations are associated with a higher risk for developing shoulder MSI and pain. STUDY DESIGN: Prospective cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 60 National Collegiate Athletic Association Division I athletes cleared for full athletic participation and free from upper extremity MSI in the last 4 weeks (age, 19.0 ± 1.2 years; weight, 82.1 ± 13.7 kg; height, 178.6 ± 11.2 cm; softball, n = 23; baseball, n = 37). Passive glenohumeral internal rotation (IR), external rotation (ER), and horizontal adduction (HA) ROM were measured with the scapula stabilized and used to categorize participants with/without external rotation gain (ERG), external rotation insufficiency (ERI), glenohumeral internal rotation deficit (GIRD), pathological GIRD, and posterior shoulder tightness (PST) before the competitive season. Groups were then compared to assess the incidence of shoulder MSI prospectively and prevalence of shoulder pain at the initial evaluation. RESULTS: Baseball and softball athletes demonstrated significantly less IR ROM in the dominant shoulder (50.6° ± 9.4°) compared with the nondominant shoulder (59.1° ± 8.6°; P < 0.01) and significantly more ER ROM (dominant, 104.6° ± 12.1°; nondominant, 97.7° ± 12.0°; P < 0.01). Incidence of shoulder MSI was 15% but was not significantly related to any shoulder adaptations. No significant relationship was found between prevalence of pain and any shoulder adaptations in the 27% of athletes with pain. CONCLUSION: Increased ER and decreased IR ROM adaptations in intercollegiate overhead throwing athletes do not appear to be correlated to risk of shoulder MSI or pain. CLINICAL RELEVANCE: The findings of this level 3 prospective study provide clinicians working with overhead athletes information regarding shoulder MSI risk and pain. It is recommended that clinicians should not use ROM adaptations exclusively to determine increased risk of shoulder MSI.

Descriptive Epidemiology of Musculoskeletal Injuries During Marine Corps Recruit Training in Gender-Integrated and Male-Only Training Units.

INTRODUCTION: Musculoskeletal injuries (MSIs) occur frequently in military personnel. U.S. Marine Corps (USMC) recruits participate in an intense 13-week training program designed to transform civilians into basically trained Marines, during which they are susceptible to MSIs. Previous injury epidemiology research with USMC recruits was conducted in a non-gender-integrated training. Data for the current study were derived from a larger study, the USMC Gender-Integrated Recruit Training study, that was initiated to provide data-driven recommendations for gender integration during USMC recruit training. The purpose of the current analysis was to describe the unique profile of MSIs during USMC recruit training and compare MSIs between female and male recruits in gender-integrated training. MATERIALS AND METHODS: Medical record-reviewed MSI data were obtained for recruits in three models of USMC recruit training: two models of gender-integrated recruit training at Marine Corps Recruit Depot (MCRD) Parris Island-the older Series Track (ST) model and the newer Integrated Company (IC) model, and a Male-Only (MO) cohort at MCRD San Diego. Incidence, anatomic region and subregion, event at the time of MSI, MSI type and onset, and disposition following MSI were described for each model. Group comparisons were conducted using Fisher's exact tests or independent samples t tests, as appropriate. RESULTS: MSI data were available for 584 recruits (ST: 98 female recruits, 95 male recruits; IC: 85 female recruits, 106 male recruits; MO: 200 male recruits). The cumulative incidence of MSIs was significantly higher among female compared to male recruits in the ST (59.2% vs. 29.5%, P < .001) and in the IC (25.9% vs. 12.3%, P = .023) cohorts. The most frequent anatomic location for MSIs was the lower extremity (female recruits: ST: 76.5% of MSIs, IC: 88.6%; male recruits: ST: 81.1%, IC: 80.0%, MO: 83.8%). The most frequent body part affected was the hip among female recruits (ST: 26.5% of MSIs, IC: 37.1%). The most frequent body part affected by MSIs among the male recruits was the knee in the ST (32.4%) and IC (53.3%) cohorts and the lower leg (27.0%) in the MO cohort. A significantly greater percentage of female compared to male recruits sustained a hip MSI in the ST (23.5% vs. 2.1%, P < .001) and IC (12.9% vs. 0.0%, P < .001) cohorts. There was no significant difference in knee MSI incidence between sexes in the ST (P = .323) or IC (P = .757) cohorts. A large percentage of MSIs resulted in light duty (female recruits: ST: 69.4% of MSIs, IC: 74.3%; male recruits: ST: 64.9%, IC: 73.3%, MO: 94.6%). CONCLUSIONS: This was the first study to assess the burden of MSIs concurrently among female and male USMC recruits in gender-integrated training. MSIs, especially those affecting the lower extremity, continue to occur frequently in this population. Female recruits are more susceptible to MSIs during USMC recruit training compared to male recruits and are especially prone to hip MSIs. Future research should focus on identifying modifiable risk factors for MSIs in this population, with a focus on reducing lower-extremity MSIs in all recruits and hip MSIs in female recruits.

Using the Capture-Recapture Technique to Estimate the Ascertainment-Corrected Incidence of Musculoskeletal Injuries During Marine Corps Recruit Training.

INTRODUCTION: Injury epidemiology research with military populations typically utilizes data obtained through medical chart review (MCR) or injury self-reports (ISRs). MCR data will not capture musculoskeletal injury (MSKI) data for which medical care was not sought, which is common during military recruit training. Injury self-report is affected by issues with recall, especially for MSKIs perceived as less severe. U.S. Marine Corps (USMC) recruits participate in an intense 13-week recruit training program during which they are susceptible to MSKIs. The purpose of the current analysis was to utilize a novel statistical method, the capture-recapture (CRC) technique, to account for the undercounting inherent in MSKI data sources and estimate the ascertainment-corrected cumulative incidence of MSKIs during USMC recruit training. MATERIALS AND METHODS: Data for the current study were derived from a larger study, the USMC Gender-Integrated Recruit Training Study, which was initiated to provide data-driven recommendations to increase gender integration in USMC recruit training. The estimated cumulative incidence of MSKIs during 13-weeks of USMC recruit training was calculated from the 2 sources of MSKI data (MCR, ISR) and using CRC analysis. Medical charts were reviewed to extract data about MSKIs that occurred during recruit training. Self-reported MSKI data for the same period were obtained from recruits at the end of recruit training. MSKIs were classified according to their anatomical location and type. The Chapman modification of the Lincoln-Peterson estimator was utilized to conduct the CRC analysis. RESULTS: Medical chart review and ISR MSKI data were available for 464 USMC recruits (age: 19.1 ± 1.9 years; gender: men 70.0%). The observed 13-week cumulative incidence of MSKI in the sample was 21.8% in the MCR and 28.4% in the ISR, while the CRC incidence was much higher (62.0%). The MCR and ISR ascertainment were 35.1% and 45.9%, respectively, while the overall ascertainment or completeness of MSKI data when 2 sources were used was moderate (65.0%). When stratified by MSKI anatomical location, the overall ascertainment varied by anatomical location of the MSKI. It was highest for lower extremity MSKIs (64.8%), but lower for upper extremity (38.9%) and spine (33.3%) MSKIs. The overall ascertainment also varied by MSKI type; it was highest for sprain (55.1%), followed by strain (54.8%), and the pain/spasm/ache (43.3%). CONCLUSIONS: This was the first study to utilize the CRC technique to access the ascertainment-corrected incidence of MSKIs among USMC recruits. There was significant undercounting in both sources of the data analyzed, and the extent of undercounting varied by both MSKI anatomical location and type. When 2 sources of data were utilized simultaneously, the percent of CRC-estimated MSKIs observed from 2 sources of data was more complete. There is a need for further application of the CRC technique to MSKI data in military populations to provide a more complete assessment of MSKIs. Identification of modifiable factors that influence completeness of MSKI data obtained during military recruit training is also warranted.

Neuromuscular Strength and Power Predict Musculoskeletal Injury and Attrition During Marine Corps Recruit Training.

INTRODUCTION: Elevated rates of musculoskeletal injuries (MSIs) and attrition are documented in military recruit training. By identifying and addressing modifiable risk factors, the rate of successful training completion and military readiness can be enhanced. Despite their impact, the causes of MSIs and attrition among U.S. Marine Corps (USMC) recruits remain underexplored. This study investigates demographic, psychological, and physiological predictors of MSIs and attrition among USMC recruits. MATERIALS AND METHODS: In this prospective cohort study, we evaluated USMC recruits at Marine Corps Recruit Depot, Parris Island and San Diego. Recruits were briefed and invited to volunteer. All recruits who were medically cleared to participate in recruit training were eligible to participate in the study. We gathered baseline data on potential predictors at the start of training, with follow-up data on MSIs and attrition collected post-training. Analyzed predictors encompassed dynamic and static strength measures from countermovement jumps, isometric mid-thigh pulls; and participant surveys. We employed multiple logistic regression to discern risk factors for MSI and attrition. RESULTS: Our study comprised 584 USMC recruits (183 female recruits, 19.49 ± 1.88 years, 160.10 ± 7.17 cm, 61.19 ± 8.05 kg; 401 males, 18.94 ± 1.92 years, 172.97 ± 7.26 cm, 73.86 ± 11.04 kg). We observed 193 MSIs in 135 recruits, with 80.31% affecting the lower extremity (LE). Notably, lower relative peak power (odds ratio [OR] 0.91 [0.89, 0.94], P < .001) and shorter eccentric deceleration duration (OR 0.99 [0.99, 1.00], P = .005) were significant predictors of MSIs. Specifically, for LE MSIs, similar trends were noted for relative peak power and eccentric deceleration duration, with additional risks associated with lower body mass index (OR 0.93 [0.86, 0.99], P = .036) and previous LE MSIs (OR 2.25 [1.18, 4.27], P = .013). Attrition was more likely with a reduced eccentric deceleration impulse (OR 0.98 [0.97, 0.99], P < .001) and prolonged time to peak force (OR 1.36 [1.17, 1.59], P < .001) and cigarette use (OR 2.12 [1.01, 4.43], P = .046). CONCLUSIONS: MSIs and attrition during USMC recruit training significantly undermine force readiness and escalate costs. Our research has pinpointed several modifiable risk factors, chiefly reduced muscular power and cigarette smoking. We advocate for neuromuscular training programs to bolster strength and power, integrated nutrition and exercise strategies for optimal body composition, and support for smoking cessation to alleviate the incidence of MSIs and curtail attrition. Initiating training with a gradual increase in activity intensity can provide a critical window to correct pre-existing neuromuscular imbalances and weaknesses, particularly those stemming from prior MSIs. Effectively addressing these risk factors is pivotal for diminishing the rates of MSIs and attrition among recruits, thereby enhancing overall military readiness and operational efficiency.

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.

Increasing Gender Integration in U.S. Marine Corps Recruit Training: Policy Recommendations and Rationales From an Interdisciplinary Study.

INTRODUCTION: This article describes alternate models and policy recommendations created by an interdisciplinary team of researchers to increase gender integration at U.S. Marine Corps (USMC) recruit training. The USMC requested a study to analyze current approaches to gender integration at recruit training and provide alternate models that maximize integration, while continuing to train marines to established standards. USMC remains the only service that segregates recruits by gender at the lowest unit level (e.g., platoon) in recruit training and maintains gender-segregated drill instructor teams (i.e., same-gender teams train platoons of same-gender recruits). MATERIALS AND METHODS: A mixed-method, interdisciplinary approach was used to capture multiple perspectives and informed recommendations and alternate models for gender integration. The team studied select USMC, army, navy, air force, and coast guard recruit training locations, between June and November 2021. At each site, the team collected qualitative, quantitative, and administrative data as well as physical performance metrics and human performance outcomes. Study participants included recruits, drill instructors, training cadre, service leaders, and subject matter experts on gender integration in military services. Each alternate model was designed to maximize the feasibility of implementation within current USMC training conditions. RESULTS: The research team developed three alternate models and several policy recommendations. Alternate model 1 proposed a methodology for mixed-gender drill instructor teams within the Integrated Company model, USMC's current integrated training model. Alternate model 2 proposed an Integrated Company Plus model which increases the number and types of gender-integrated training events at or below the platoon level within the Integrated Company model. Alternate model 3 outlined an integrated platoon model where recruits fall out into integrated training platoons after their morning routine, with two options of varying integration based on USMC priorities for integration. The team also proposed a set of policy recommendations independent of the three alternate models to support current and future gender integration efforts at the Marine Corps Recruit Depots. CONCLUSIONS: Gender-integrated military training has been shown to positively alter perceptions and evaluations of women in military settings over detrimental aspects developed by gender-segregated training. The study team recommended USMC train recruits in the Integrated Company model with mixed-gender drill instructor teams (alternate model 1) and integrate more training events following the priority tiers outlined in the Integrated Company plus model (alternate model 2). The combined execution of these two alternate models would provide USMC recruits increased exposure to direct, sustained training from opposite-gender drill instructors and deliver intentional training opportunities for male and female recruits to work together and interact in meaningful ways. The integrated platoon model (alternate model 3) would offer USMC recruits the most direct exposure to training and working with members of the opposite gender, but it requires substantial changes to current logistics, accountability, and training procedures.

Local anaesthetics use does not suppress muscle activity following an ankle injection.

PURPOSE: To determine if peroneus longus (PL), peroneus brevis (PB), medial gastrocnemius (MG) and tibialis anterior (TA) muscle activation patterns during inversion perturbation and running tasks are suppressed following lidocaine injection to the anterior talofibular (ATF) and calcaneofibular (CF) ligament regions. METHODS: Fourteen recreationally active male subjects (age, 24.8 ± 2.9 years; height, 177.0 ± 6.0 cm; mass, 77.7 ± 6.7 kg) participated. Testing was performed under five injection conditions to the ATF and CF regions: 1 ml saline, 1 ml lidocaine, 3 ml saline, 3 ml lidocaine or no injection. Following injection condition, traditional ankle taping was applied. Electromyography patterns of the PL, PB, MG and TA were collected while subjects performed continuous lateral jumps on a custom-built device which elicited an ankle inversion perturbation and treadmill running (3.35 m s(-1), 0.5 % incline). RESULTS: No significant differences were demonstrated in muscle activation patterns of the PL (n.s.), PB (n.s.), MG (n.s.) or TA (n.s.) for any variable across injected conditions during both tasks. Statistical power was 0.214-0.526 for the PL, 0.087-0.638 for the PB, 0.115-0.560 for the MG and 0.118-0.410 for the TA. CONCLUSIONS: Injection of lidocaine up to 3 ml to the ATF and CF regions did not suppress muscle activity of the PL, PB, MG or TA during the inversion perturbation or running tasks. Injection up to 3 ml of 1 % lidocaine to the ATF and CF regions may be used without sacrificing the muscle activation patterns about the ankle. This finding is clinically relevant since the use of the injection does not put the patient at any higher risk of reinjury to the site.

Epidemiology of Musculoskeletal Injuries Among Naval Special Warfare Personnel.

BACKGROUND: Musculoskeletal injuries (MSIs) are an important cause of morbidity in the military, especially among Special Forces. The aim of this analysis was to describe MSIs among two groups of Naval Special Warfare (NSW) personnel-Special Warfare Combatant-Craft Crewman (SWCC) Operators and Crewman Qualification Training (CQT) students. METHODS: In this cross-sectional study, we describe self-reported MSIs that occurred during a one-year period and the calculated financial costs of MSIs. Group comparisons were conducted using Fisher's exact tests and independent samples t tests. RESULTS: Data were available for 142 SWCC Operators (26.9 ± 5.9 years, 1.8 ± 0.1 meters, 85.4 ± 10.4 kilograms) and 187 CQT students (22.8 ± 3.2 years, 1.8 ± 0.2 meters, 81.4 ± 8.9 kilograms). The one-year cumulative MSI incidence was significantly lower among SWCC Operators (21.1%) compared to CQT students (37.4%, p = 0.002). The most common anatomic location for MSIs was the lower extremity (SWCC: 50.0% of MSIs, CQT: 66.3%). Physical training was the predominant activity when MSIs occurred (SWCC: 31.6%, CQT: 77.6%). The lifetime cost of all the MSIs included in the analysis was approximately $580,000 among 142 SWCC Operators and $1.2 million among 187 CQT students. CONCLUSION: MSIs, especially those affecting the lower extremity and occurring during physical training, cause considerable morbidity and financial burden among NSW personnel. Many of the musculoskeletal injuries are to musculotendinous tissue, which typically results from tissue overload or inadequate recovery. Further investigation of the preventable causes of these MSIs and development of a customized, evidence-based MSI prevention program is required to reduce the burden of these MSIs.

Incidence and pattern of musculoskeletal injuries among women and men during Marine Corps training in sex-integrated units.

OBJECTIVES: The purpose of this analysis was to describe and compare the incidence and pattern of musculoskeletal injuries in women and men during the United States Marine Corps Ground Combat Element Integrated Task Force work-up and assessment phases in sex-integrated units. DESIGN: Descriptive cross-sectional study. METHODS: Certified athletic trainers and Navy corpsmen reported injury data for 302 Marines (women: 27.8%, men: 72.2%). Injury frequency, location, cause, type, and activity during injury were described. Fisher's exact tests were used to compare proportions of injured women and men. The cost of injuries was calculated using the Web-based Injury Statistics Query and Reporting System. RESULTS: A greater proportion of women (40.5%) sustained an injury compared with men (18.8%, p < 0.001). The lower extremity was the most frequent location for injury (women: 68% of injuries, men: 60%). The most frequent sub-location was the hip (24%) in women and foot/toes (26%) in men. Marching under load was the most common cause (women: 64%, men: 48%). Most injuries occurred during physical training (women: 78%, men: 66%), and were classified as pain/spasm/ache (women: 56%, men: 36%). The total lifetime cost of these injuries that occurred among 302 Marines was approximately $1.4 million U.S. dollars. CONCLUSIONS: The high risk of lower extremity injuries that occurred while marching under load during physical training, and the greater risk of injuries among women compared to men, indicates the need for further research to identify the components of combat Military Occupational Specialty specific training that could be modified to mitigate injuries.

Fight load index and body composition are most associated with combat fitness in female Marines.

Optimizing tactical fitness is important for combat readiness and injury prevention, especially as women have entered ground combat military occupational specialties. OBJECTIVES: To assess characteristics of male and female Marines by Combat Fitness Test (CFT) performance clusters. DESIGN: Cross-sectional study. METHODS: Anthropometric, body composition (BF%, fat and fat-free mass [FM and FFM], and Fight load index [FLI], physiological (maximal oxygen uptake, lactate threshold and anaerobic power/capacity), and musculoskeletal (isokinetic strength of the knee, shoulder, torso, and isometric strength of the ankle) assessments were obtained from 294 male (M) and female (F) Marines. Hierarchical cluster analysis classified Marines based on performance of two CFT events (sec): Maneuver Under Fire (MANUF) and Movement to Contact (MTC). Following tests for normality, one-way ANOVA or Kruskal Wallis tests, followed by Bonferroni post-hoc tests, assessed characteristics across clusters and sex (alpha=0.05). RESULTS: Two clusters (C) were determined: C1: N=66F, 16M and C2: N=18F, 194M, with C2 demonstrating better performance on the MANUF and MTC. C1F demonstrated significantly greater BF% and FLI than C1M, C2F, and C2M. C2M demonstrated significantly greater knee flexion strength than C1F and C2F, but C1M was only significantly greater than C1F. C2M demonstrated significantly greater ankle eversion and inversion strength than C1F. CONCLUSIONS: Women with increased BF%, increased FM and reduced FFM relative to a fighting load may have decreased performance in combat-related tasks. Training programs based on an individual Marine's baseline body composition and fitness characteristics can enhance combat fitness and force readiness.

Epidemiology of musculoskeletal injuries among US Air Force Special Tactics Operators: an economic cost perspective.

OBJECTIVES: Musculoskeletal injuries (MSI) are an important concern in military populations. The purpose of this study was to describe the burden of MSI and associated financial cost, in a sample of US Air Force Special Operations Command Special Tactics Operators. METHODS: In this cross-sectional study, medical records of the Operators were reviewed during the years 2014-2015. MSI that occurred during a 1-year period prior to the date of review were described. MSI attributes described included incidence, anatomic location, cause, activity when MSI occurred, type and lifetime cost of MSI estimated using the Web-based Injury Statistics Query and Reporting System. RESULTS: A total of 130 Operators participated in the study (age: 29.1±5.2 years). The 1-year cumulative incidence of MSI was 49.2 injured Operators/100 Operators/year. The most frequent anatomic location and sublocation for MSI were the lower extremity (40.9% of MSI) and shoulder (20.9%), respectively. Lifting was a common cause of MSI (21.8%). A large per cent of MSI (55.5%) occurred while Operators were engaged in either physical or tactical training. Common MSI types were pain/spasm/ache (44.5%). Many MSI (41.8%) were classified as potentially preventable by an injury prevention training programme. The total lifetime cost of these MSI was estimated to be approximately US$1.2 million. CONCLUSION: MSI are an important cause of morbidity and financial cost in this sample of Air Force Special Tactics Operators. There is a need to develop a customised injury prevention programme to reduce the burden and cost of MSI in this population.

Using the capture-recapture method to estimate the incidence of musculoskeletal injuries among U.S. Army soldiers.

Musculoskeletal injury (MSI) data typically are obtained from medical chart-review (MCR) or injury self-reports (ISR). MSI incidence may be under-counted if only one source is utilized, as MCR will not capture MSI for which medical care was not sought, and ISR may be affected by issues with recall. OBJECTIVES: The purposes of this study were to determine MSI incidence from two sources (MCR, ISR) and to estimate the incidence, after accounting for the under-counting in both sources, among a sample of U.S. Army soldiers. DESIGN: Descriptive cross-sectional study. METHODS: The estimated cumulative incidence during a one-year period was calculated from the two sources of MSI data using a novel statistical analysis (capture-recapture-CRC). RESULTS: MSI data were available for 287 soldiers (age: 27.5±6.3years (mean±standard deviation)). The one-year cumulative incidence of MSI was 17.8% (MCR), 19.5% (ISR), and 54.0% (CRC). CRC analysis showed that there was under-counting from both sources of data and the percent of CRC estimated MSI observed were 32.9% (MCR), 36.1% (ISR), and 57.4% (MCR and ISR combined). When analyzed by MSI type, percent of CRC estimated MSI counted from both sources was highest (75.0%) for fracture, followed by sprain (53.8%), strain (43.8%), and pain/spasm/ache (35.8%). CONCLUSIONS: There was under-counting of MSI from both sources of data, and the under-counting varied by MSI type. There is a need for further investigation of the relative benefits of various sources of MSI data and the application of the capture-recapture analysis in military populations.

Kinesiology taping does not alter shoulder strength, shoulder proprioception, or scapular kinematics in healthy, physically active subjects and subjects with Subacromial Impingement Syndrome.

OBJECTIVE: To examine the effect of kinesiology tape (KT) on shoulder strength, proprioception, and scapular kinematics in healthy and Subacromial Impingement Syndrome (SAIS) subjects. DESIGN: Placebo-controlled quasi-experimental study. SETTING: Research laboratory. PARTICIPANTS: A total of 30 physically active subjects participated. Ten healthy subjects with no previous history of shoulder pathology received KT on the dominant shoulder. Twenty subjects with shoulder pain for a minimum of two weeks and presenting with clinical signs of impingement were allotted to receive KT (n = 10) or placebo taping (PT, n = 10) on the involved shoulder. MAIN OUTCOME MEASURES: All participants were tested pre- and post-application. Shoulder internal/external rotation (IR/ER) strength was assessed with isokinetic dynamometry (average peak torque/body weight). Shoulder IR/ER proprioception was assessed through threshold to detect passive motion (mean absolute error in degrees). Scapular position at 90° and 120° of shoulder abduction during arm raising/lowering were assessed using a 3D motion analysis system. RESULTS: No significant within group or between group differences were demonstrated for any measure. CONCLUSIONS: Taping does not appear to aid/impair shoulder strength, shoulder proprioception, or scapular kinematics. Future research should explore if the effects of KT are time-dependent and similar in other pathologies.

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.

Association of prospective lower extremity musculoskeletal injury and musculoskeletal, balance, and physiological characteristics in Special Operations Forces.

OBJECTIVES: Previous research has examined lower extremity (LE) musculoskeletal injury (MSI) patterns and risk factors in Special Operations Forces (SOF) trainees, conventional military personnel, and athletes; however, it is unclear if SOF have the same patterns/risk factors. This study aimed to determine the association of musculoskeletal, balance, and physiological characteristics with LE MSI in SOF. DESIGN: Cohort study. METHODS: A total of 726 Air Force (N=140), Navy Sea, Air, and Land (N=301), and Special Warfare Combatant Crewmen (N=285) SOF (age=25.72±4.77years, height=178.34±6.63cm, weight=84.28±9.03kg) participated in laboratory testing, including: LE muscular strength and flexibility; balance; body composition; anaerobic power/capacity; and aerobic capacity. Medical charts were reviewed for LE MSI 365days following laboratory testing. Participants were assigned by injury status and laboratory data stratified by tertile. Chi-square statistics were calculated to determine the frequency of LE MSI across tertiles for each characteristic. RESULTS: There was a significant association between LE MSI and: ankle inversion strength (weaker side: Χ(2)=17.703; stronger side: Χ(2)=18.911; p≤0.001); ankle eversion/inversion strength ratio (lower side: Χ(2)=13.456; higher side: Χ(2)=16.885; p≤0.001); hamstring flexibility (less flexible: Χ(2)=19.930; more flexible Χ(2)=15.185; p≤0.001); gastrocnemius-soleus flexibility (less flexible: Χ(2)=7.889, p=0.019); dynamic balance asymmetry (Χ(2)=7.444, p=0.024); Vestibular and Preference ratios (Χ(2)=9.124, p=0.010 and Χ(2)=6.572, p=0.037, respectively); and aerobic capacity (Χ(2)=13.935, p=0.001). CONCLUSIONS: Characteristics associated with LE MSI are unique in SOF. Human performance program initiatives should include efforts to optimize ankle strength and flexibility, maintain moderate hamstring flexibility, expand dynamic balance strategies, and maximize aerobic capacity to reduce LE MSI risk.

Epidemiology of musculoskeletal injuries sustained by Naval Special Forces Operators and students.

OBJECTIVES: The aim of this analysis was to describe the incidence and common types of medical chart-reviewed musculoskeletal injuries, among four distinct groups of Naval Special Warfare (NSW) personnel: Sea, Air, and Land (SEAL) Operators, SEAL Qualification Training (SQT) students, Special Warfare Combatant-craft Crewman (SWCC) Operators, and Crewman Qualification Training (CQT) students. DESIGN: Descriptive cross-sectional study. METHODS: Medical records were reviewed for 920 NSW personnel. MSI were described and classified by frequency and incidence; anatomic location; injury type and cause; activity during injury; and potential for prevention. RESULTS: The frequency of MSI was 23.1, 46.5, 31.6, and 17.0 per 100 participants per year among SEAL, SQT, SWCC, and CQT, respectively. Upper extremity MSI were the most common in SEAL, lower extremity MSI were common in the other groups. The most frequent MSI anatomic sub-locations varied across groups (SEAL: shoulder, 21.6% of MSI; SQT: foot and toes, 17.0%; SWCC: lumbopelvic spine, 21.7%; and CQT: knee, 30.3%). Pain/spasm/ache were the most common MSI type in SEAL (29.7%) and SWCC (21.7%), tendonitis/tenosynovitis/tendinopathy was the most common MSI type in SQT (21.0%), and tendonitis/tenosynovitis/tendinopathy and fracture were the most common in CQT (15.2% each). A considerable proportion of MSI were classified as potentially preventable-SEAL: 35.1%, SQT: 53.0%, SWCC: 36.7%, and CQT: 21.2%. CONCLUSIONS: MSI cause considerable morbidity among NSW Operators and students, with distinct patterns of distribution by anatomic location and injury type. Since many injuries may be preventable, targeted interventions may be able to mitigate MSI risk.

Effects of Deployment on Musculoskeletal and Physiological Characteristics and Balance.

Despite many nonbattle injuries reported during deployment, few studies have been conducted to evaluate the effects of deployment on musculoskeletal and physiological characteristics and balance. A total of 35 active duty U.S. Army Soldiers participated in laboratory testing before and after deployment to Afghanistan. The following measures were obtained for each Soldier: shoulder, trunk, hip, knee, and ankle strength and range of motion (ROM), balance, body composition, aerobic capacity, and anaerobic power/capacity. Additionally, Soldiers were asked about their physical activity and load carriage. Paired t tests or Wilcoxon tests with an α = 0.05 set a priori were used for statistical analyses. Shoulder external rotation ROM, torso rotation ROM, ankle dorsiflexion ROM, torso rotation strength, and anaerobic power significantly increased following deployment (p < 0.05). Shoulder extension ROM, shoulder external rotation strength, and eyes-closed balance (p < 0.05) were significantly worse following deployment. The majority of Soldiers (85%) engaged in physical activity. In addition, 58% of Soldiers reported regularly carrying a load (22 kg average). The deployment-related changes in musculoskeletal and physiological characteristics and balance as well as physical activity and load carriage during deployment may assist with proper preparation with the intent to optimize tactical readiness and mitigate injury risk.

Lumbar spine and hip flexibility and trunk strength in helicopter pilots with and without low back pain history.

BACKGROUND: Low back pain (LBP) is one of the most common musculoskeletal issues facing military helicopter pilots. It is clinically important to identify differences in musculoskeletal characteristics between pilots with and without a LBP history for formulating effective interventions. OBJECTIVE: To compare lumbar spine and hip flexibility and trunk strength in pilots with and without a LBP history. METHODS: A total of 30 pilots with a LBP history were matched with pilots without a LBP history. An isokinetic dynamometer and a digital inclinometer were used to evaluate trunk and hip strength and a range-of-motion (ROM), respectively. All tests were performed bilaterally, if applicable, and agonist/antagonist ratios and side-to-side (low/high) symmetries were calculated. Paired t-tests or Wilcoxon tests were used to assess group differences (p <  0.050). RESULTS: The LBP group demonstrated significantly lower trunk extension strength and trunk extension/flexion strength ratio (p <  0.008). The LBP group demonstrated significantly less lateral flexion ROM as well as greater lateral flexion and rotation side-to-side asymmetry (p <  0.009). The LBP group demonstrated significantly greater total hip rotation side-to-side asymmetry (p = 0.037). CONCLUSIONS: Given the results, specific exercises that are targeted to improve trunk strength, ROM, and side-to-side symmetries could be developed to reduce LBP in helicopter pilots.