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

Body composition as a marker of performance and health in military personnel

Introduction

Body composition standards are set to ensure operational readiness in active-duty military personnel. To meet body composition standards, some individuals, however, may engage in unhealthy weight control behaviors (i.e., weight cycling and disordered eating). The objectives of this review are to: (1) evaluate the evidence regarding body composition and the associations to physical and military specific performance; (2) discuss body composition and potential health consequences; and (3) examine the evidence of weight cycling and disordered eating behaviors in military personnel for weight control.

Methods

A systematic search to identify peer-reviewed research articles was conducted in PubMed on 2/20/2023 using Medical Subject Headings (MeSH) including but not limited to "Military Personnel", "Tactical Athlete", "Weight Loss", "Body Composition", and "Weight Cycling".

Results

A total of 225 research articles were identified. The list was narrowed down to articles from the last 20 years (2003-2023) in military personnel. Only studies in which percent body fat was directly measured were included resulting in 17 research articles for this review.

Discussion

Evidence-based research is limited on the relationship between body composition and operational readiness. Weight cycling and disordered eating behaviors also has been reported for weight control, yet additional research is needed. Specifically, future research should focus on female service members, racial and ethnic differences, age, and postpartum status and include other service branches (i.e., Air Force and Navy). A comprehensive survey on weight cycling, disordered eating, and weight management would be valuable to determine the prevalence and extent of this issue. This information along with performance data would guide policy makers on the relevance and appropriateness of existing body composition standards.

Financial Impact of Embedded Injury-Prevention Experts in US Army Initial Entry Training

CONTEXT

The US Army embedded injury-prevention experts (IPEs), specifically athletic trainers and strength and conditioning coaches, into initial entry training (IET) to limit musculoskeletal (MSK) conditions and their negative consequences. However, little is known about the financial impact of IPEs.

OBJECTIVE

To assess whether IPEs were associated with fewer sunk training costs due to MSK-related early discharges from service.

DESIGN

Retrospective cohort study.

SETTING

Database of US Army soldiers' administrative, medical, and readiness records.

PATIENTS OR OTHER PARTICIPANTS

A total of 198 166 soldiers (age = 20.7 ± 3.2 years, body mass index = 24.4 ± 3.5 kg/m2) who began IET during 2014 to 2017.

MAIN OUTCOME MEASURE(S)

Early discharge from service was defined as occurring within 6 months of beginning IET. All IET sites employed IPEs from 2011 to 2017, except for 2 sites during April to November 2015. Soldiers who began IET at these 2 sites during these times were categorized as not having IPE exposure. All others were categorized as having IPE exposure. The unadjusted association between IPE access and MSK-related early discharge from service was assessed using logistic regression. Financial impact was assessed by quantifying differences in yearly sunk costs between groups with and those without IPE exposure and subtracting IPE hiring costs.

RESULTS

Among 14 094 soldiers without IPE exposure, 2.77% were discharged early for MSK-related reasons. Among 184 072 soldiers with IPE exposure, 1.01% were discharged. Exposure to IPEs was associated with reduced odds of MSK-related early discharge (odds ratio = 0.36, 95% CI = 0.32, 0.40, P < .001) and a decrease in yearly sunk training costs of $11.19 to $20.00 million.

CONCLUSIONS

Employing IPEs was associated with reduced sunk costs because of fewer soldiers being discharged from service early for MSK-related reasons. Evidence-based recommendations should be developed for guiding policy on the roles and responsibilities of IPEs in the military to reduce negative outcomes from MSK conditions and generate a positive return on investment.

Force plate vertical jump scans are not a valid proxy for physical fitness in US special warfare trainees

Background: The United States Air Force Special Warfare Training Wing (SWTW) administers a comprehensive physical fitness test to active duty Airmen entering the Special Warfare training pipeline. The Sparta Science™ system utilizes proprietary software to analyze the force-time curve of a vertical jump and purports to serve as a proxy for traditional military fitness tests. The Sparta Science™ system produces four proprietary metrics, including the Sparta™ Score, which is correlated to high magnitudes of force production purportedly performance. This study investigated how Sparta™ Jump Scans correlate to components of a physical fitness test utilized within the SW training pipeline. Methods: At the entry and exit of an 8-week Special Warfare Training Wing preparatory course (SW PREP), 643 trainees completed both an initial and final Sparta™ Jump Scan and a Candidate Fitness Test (CFT). The Candidate Fitness Test consists of eight components and tests several different domains of fitness including strength, power, muscular endurance, swimming proficiency, and cardiovascular fitness. Paired t-tests were used to determine if Sparta™ Jump Scan metrics and CFT components changed during SW PREP. Sparta™ Score's correlation was assessed against every other Sparta™ Jump Scan metric and all CFT fitness measures. Results: This study found that the Sparta™ Jump Scan metrics decline slightly over SW PREP (p < 0.05; negligible-small effect size), while most CFT measures improve (p < 0.05; small-medium effect size). Changes in Sparta™ Jump Scan metrics did not reflect the changes in CFT performance over SW PREP (r ²: 0.00-0.03). Conclusion: The Sparta™ Score was not correlated to the most tactically-relevant fitness measures (rucking and swimming), and only weakly correlated with the only jumping measure on the fitness test, the standing broad jump.

Lessons From Special Forces Operators for Elite Team Sports Training: How to Make the Whole Greater Than the Sum of the Parts

This methodology paper describes the design of a holistic and multidisciplinary human performance program within the Belgian Special Forces Group, the Tier 1 Special Operations unit of the Belgian Defense. Performance management approaches in the military draw heavily on sports science. The key component of the program design described here is its integrative nature, which team sports training might benefit from. The basic rationale behind the program was to bridge several gaps: the gap between physical and mental training; the gap between the curative or preventive medical approach and the performance enhancement approach; and the gap between individual and team training. To achieve this goal, the methodology of Intervention Mapping was applied, and a multidisciplinary team of training and care professionals was constituted with operational stakeholders. This was the first step in the program design. The second step took a year, and consisted of formal and informal consultations, participant observations and task analyses. These two first stages and their conclusions are described in the Method section. The Results section covers the next two stages (three and four) of the process, which aimed at defining the content of the program; and to test a pilot project implementation. The third stage encompassed the choice of the most relevant assessment and intervention tools for the target population, within each area of expertise. This is described extensively, to allow for replication. The fourth and last stage was to "test drive" the real-life integration and implementation of the whole program at the scale of a single team (8 individuals). For obvious confidentiality reasons, the content data will not be reported extensively here. Implications for wider-scale implementation and tie-back to sports team training are presented.

Risk factors for musculoskeletal injuries in the military: a qualitative systematic review of the literature from the past two decades and a new prioritizing injury model

BACKGROUND

Musculoskeletal injuries (MSkIs) are a leading cause of health care utilization, as well as limited duty and disability in the US military and other armed forces. MSkIs affect members of the military during initial training, operational training, and deployment and have a direct negative impact on overall troop readiness. Currently, a systematic overview of all risk factors for MSkIs in the military is not available.

METHODS

A systematic literature search was carried out using the PubMed, Ovid/Medline, and Web of Science databases from January 1, 2000 to September 10, 2019. Additionally, a reference list scan was performed (using the "snowball method"). Thereafter, an international, multidisciplinary expert panel scored the level of evidence per risk factor, and a classification of modifiable/non-modifiable was made.

RESULTS

In total, 176 original papers and 3 meta-analyses were included in the review. A list of 57 reported potential risk factors was formed. For 21 risk factors, the level of evidence was considered moderate or strong. Based on this literature review and an in-depth analysis, the expert panel developed a model to display the most relevant risk factors identified, introducing the idea of the "order of importance" and including concepts that are modifiable/non-modifiable, as well as extrinsic/intrinsic risk factors.

CONCLUSIONS

This is the qualitative systematic review of studies on risk factors for MSkIs in the military that has attempted to be all-inclusive. A total of 57 different potential risk factors were identified, and a new, prioritizing injury model was developed. This model may help us to understand risk factors that can be addressed, and in which order they should be prioritized when planning intervention strategies within military groups.

Relationships between balance and physical fitness variables in firefighter recruits

BACKGROUND

Research has suggested that balance ability contributes to musculoskeletal injury (MSKI) rates in firefighters. Though the Y-Balance Test (YBT) can predict injury, it is unclear what physical measures inform YBT performance in firefighters. Thus, there is a lack of knowledge regarding best practice for improving balance in firefighters.

OBJECTIVE

To evaluate the relationship between the YBT and fitness measures, including body composition, aerobic capacity, functional total-body power, upper and lower-body strength, and movement efficiency, among firefighters.

METHODS

Dynamic balance (YBT), body mass index (BMI), body-fat percentage (BF%), fat free mass (FFM), aerobic capacity (VO2max), stair climb (SC), upper (1RMbench) and lower-body (1RMsquat) strength, and Fusionetics™ Movement Efficiency Screen (ME) measures were collected among 35 firefighter recruits. Pearson correlation coefficients were used to examine relationships between YBT and the performance measures.

RESULTS

Dynamic balance ability in firefighter recruits is significantly (p < 0.05) related to BMI, lower-body strength, and movement quality, but not with aerobic capacity, stair climb performance, and upper body strength.

CONCLUSIONS

Greater YBT performance in firefighter recruits is associated with lower BMI, greater functional movement, and greater lower-body strength. Future research is warranted to incorporate these elements into balance training programs for firefighter recruits.

Much work remains to reach consensus on musculoskeletal injury risk in military service members: A systematic review with meta-analysis

Musculoskeletal injuries are the most common reason military service members cannot perform their military duties. Not only are they costly and associated with long-term disability, often long after completion of military service, but injuries also adversely affect the military readiness of a nation. This can be seen as a threat to national security and part of the impetus behind many efforts to better understand, predict, and mitigate injury risk in the military. A systematic review of the literature published between 1995 and October 31, 2020 was conducted to identify significant risk factors of musculoskeletal injury in military populations across the world. 74 out of 170 eligible studies addressed comprehensive injuries, providing 994 unique risk factors. 46 of these studies provided data that could be included in a meta-analysis, which was possible for 15 predictor variables. Seven predictors were significant in meta-analysis: female sex(RR=1.46;95CI 1.30,1.64), high body mass index(RR=1.36;95CI 1.21,1.53), functional movement screen pain (RR=1.70;95CI 1.55,1.87) or scores ≤ 14(RR=1.42 95CI 1.29,1.56), prior injury(RR=1.54;95CI 1.32,1.80), slower running performance(RR=1.33;95CI 1.18,1.51), and poorer push-up performance(RR=1.15;95CI 1.04,1.27). Low BMI, height, weight, smoking, physical activity scores, and sit-up and jump performance were not significant risk factors in the meta-analysis. Most studies had a high risk of bias. Lack of raw data and large heterogeneity in definitions of predictors and injury outcomes limited comparison across many studies.Highlights Female sex, high body mass index, pain with functional movement screen or a score of ≤ 14, prior injury, slower running performance and poorer push-up performance were all significant predictors of musculoskeletal injury.Low body mass index, height, weight, smoking, physical activity scores, and sit-up and jump performance were not significant predictors of musculoskeletal injury.Many other predictors were present only in single studies, but large heterogeneity in definitions of both outcomes and predictors limited comparison across studies.Overall, studies assessing risk factors to predict musculoskeletal injuries in the military were at high risk for bias, especially in regards to statistical approaches.

THE RELIABILITY AND MINIMAL DETECTABLE CHANGE OF THE ELY AND ACTIVE KNEE EXTENSION TESTS

Background

Muscle length is a common component of the physical therapy examination, which may include the prone knee flexion (Ely) and active knee extension (AKE) tests. Clinicians using these tests should understand the clinimetric properties.

Purpose

To investigate the reliability and minimal detectable change (MDC₉₅) of the Ely and AKE tests.

Study Design

Reliability analysis.

Methods

Seventy-one asymptomatic adults (mean age 24.6 + /- 2.8 years) were recruited based on a convenience sample. Two examiners each performed the Ely and AKE test one time each in an intrasession design for the interrater reliability component, with one examiner repeating the tests one time 48 hours later to determine the intra-rater reliability. Results were recorded based on one trial per test and utilized a pelvic strap for the Ely test and an adjustable bolster for the AKE test. A separate researcher recorded measurements and results were blinded from the examiners.

Results

The Ely test had excellent intra-rater and inter-rater reliability with an intraclass correlation coefficient (ICC) (3,1) of 0.900 and ICC (2,1) of 0.914 respectively. The intra-rater and inter-rater reliability of the AKE test was good with ICC (3,1) of 0.882 and ICC (2,1) 0.886 respectively. The MDC₉₅ indicated that a change greater than or equal to 8° and 12° is required to exceed the threshold of error for the Ely and AKE test respectively.

Conclusion

The Ely and AKE tests have good to excellent inter-rater and intra-rater reliability for measuring rectus femoris and hamstring muscle length when stabilization of the pelvis and hip is accounted for. The MDC should be considered as a threshold for true change in the asymptomatic adult population.

Levels of Evidence

2b.

Identification of Risk Factors Prospectively Associated With Musculoskeletal Injury in a Warrior Athlete Population

BACKGROUND

Musculoskeletal injuries are a primary source of disability. Understanding how risk factors predict injury is necessary to individualize and enhance injury reduction programs.

HYPOTHESIS

Because of the multifactorial nature of musculoskeletal injuries, multiple risk factors will provide a useful method of categorizing warrior athletes based on injury risk.

STUDY DESIGN

Prospective observational cohort study.

LEVEL OF EVIDENCE

Level 2.

METHODS

Baseline data were collected on 922 US Army soldiers/warrior athletes (mean age, 24.7 ± 5.2 years; mean body mass index, 26.8 ± 3.4 kg/m²) using surveys and physical measures. Injury occurrence and health care utilization were collected for 1 year. Variables were compared in healthy versus injured participants using independent t tests or chi-square analysis. Significantly different factors between each group were entered into a logistic regression equation. Receiver operating characteristic curve and accuracy statistics were calculated for regression variables.

RESULTS

Of the 922 warrior athletes, 38.8% suffered a time-loss injury (TLI). Overall, 35 variables had a significant relationship with TLIs. The logistic regression equation, consisting of 11 variables of interest, was significant (adjusted R² = 0.21; odds ratio, 5.7 [95% CI, 4.1-7.9]; relative risk, 2.5 [95% CI, 2.1-2.9]; area under the curve, 0.73). Individuals with 2 variables had a sensitivity of 0.89, those with 7 or more variables had a specificity of 0.94.

CONCLUSION

The sum of individual risk factors (prior injury, prior work restrictions, lower perceived recovery from injury, asymmetrical ankle dorsiflexion, decreased or asymmetrical performance on the Lower and Upper Quarter Y-Balance test, pain with movement, slower 2-mile run times, age, and sex) produced a highly sensitive and specific multivariate model for TLI in military servicemembers.

CLINICAL RELEVANCE

A better understanding of characteristics associated with future injury risk can provide a foundation for prevention programs designed to reduce medical costs and time lost.

The Relationship Between Army Physical Fitness and Functional Capacities in Infantry Members of the Slovenian Armed Forces

Šimenko, J, Kovčan, B, Pori, P, Vodičar, J, Vodičar, M, and Hadžić, V. The Relationship between army physical fitness and functional capacities in infantry members of the Slovenian Armed Forces. J Strength Cond Res XX(X): 000-000, 2019-The primary purpose of this study was to determine the relationship between traditional army physical fitness test (APFT) and a novel functional testing battery that included counterMovement jump (CMJ) testing, stork balANce test, pUll-ups, single leg hAmstring bridge test, and loaded prone pLank test-MANUAL battery. The secondary purpose was to explore additional baseline fitness aspects traditionally not covered by APFT. This cross-sectional study involved 181 Slovenian Armed Forces (SAF) infantry members (age 31.4 ± 6.1 years) that were tested using both the regular annual APFT and the MANUAL battery (testing was conducted 2 weeks apart). At the significance level of p ≤ 0.05, significant but weak associations between the MANUAL testing battery and APFT battery (0.2 ≦ r < 0.5; p ≤ 0.05) were observed. The MANUAL battery has highlighted possible hamstring (less than 20 repetitions on a single leg bridge test in 26% of SAF infantry members) and posterior shoulder pull-up muscle weakness (mean score 5 ± 4 pull-ups). Functional predictors from the MANUAL explained only 33.6% of the APFT score (R = 0.336). Significant predictors of APFT score were single leg hamstring left (p = 0.048), loaded plank (p = 0.049), number of pull-ups (p < 0.001), CMJ (p = 0.01), and loaded CMJ (p = 0.026). The findings suggest that higher APFT marks are associated with better performance on the MANUAL tests and indicate the problem of hamstring and pull-up muscle weakness. The general recommendation is that the physical condition military programs should include more exercises to strengthen those muscle groups.

Is Poor Hamstring Flexibility a Risk Factor for Hamstring Injury in Gaelic Games?

Context:Hamstring injuries are a leading cause of injury in Gaelic games. Hamstring flexibility as a risk factor for hamstring injury has not yet been examined prospectively in Gaelic games.Objective:To examine whether hamstring flexibility, using the modified active knee extension (AKE) test, and previous injury are risk factors for hamstring injury in Gaelic players and to generate population-specific AKE cutoff points.Design:Prospective cohort study.Setting:School and colleges.Patients (or Other Participants):Adolescent and collegiate Gaelic footballers and hurlers (n = 570).Intervention(s):The modified AKE test was completed at preseason, and hamstring injuries were assessed over the course of one season. Any previous hamstring injuries were noted in those who presented with a hamstring injury.Main Outcome Measures:Bilateral AKE scores and between-leg asymmetries were recorded. Receiver operating characteristic curves were implemented to generate cutoff points specific to Gaelic players. Univariate and backward stepwise logistic regression analyses were completed to predict hamstring injuries, hamstring injuries on the dominant leg, and hamstring injuries on the nondominant leg.Results:Mean flexibility of 64.2° (12.3°) and 64.1° (12.4°) was noted on the dominant and nondominant leg, respectively. Receiver operating characteristic curves generated a cutoff point of < 65° in the AKE on the nondominant leg only. When controlled for age, AKE on the nondominant leg was the only predictor variable left in the multivariate model (odds ratio = 1.03) and significantly predicted hamstring injury (χ2 = 9.20,P = .01). However, the sensitivity was 0% and predicted the same amount of cases as the null model. It was not possible to generate a significant model for hamstring injuries on the dominant leg (P > .05), and no variables generated aPvalue < .20 in the univariate analysis on the nondominant leg.Conclusions:Poor flexibility noted in the AKE test during preseason screening and previous injury were unable to predict those at risk of sustaining a hamstring strain in Gaelic games with adequate sensitivity.

The Warrior Model for Human Performance Optimization

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