Soldier Load Carriage, Injuries, Rehabilitation and Physical Conditioning: An International Approach

Physiological characteristics predictive of passing military physical employment standard tasks for ground close combat occupations in men and women

Challenges for some women meeting the physical employment standards (PES) for ground close combat (GCC) roles stem from physical fitness and anthropometric characteristics. The purpose of this study was to identify the modifiable and nonmodifiable characteristics predictive of passing GCC-based PES tasks and determine the modifiable characteristics suitable to overcome nonmodifiable limitations. 107 adults (46 women) underwent multiday testing assessing regional and total lean mass (LM), percent body fat (BF%), aerobic capacity (V̇O2peak), strength, power, and PES performance. Predictors with p-value <0.200 were included in stepwise logistic regression analysis or binary logistic regression when outcomes among sexes were insufficient. Relative and absolute arm LM (OR: 4.617-8.522, p < 0.05), leg LM (OR: 2.463, p < 0.05), and upper body power (OR: 2.061, p < 0.05) predicted medicine ball chest throw success. Relative and absolute arm LM (OR: 3.734-11.694, p < 0.05), absolute trunk LM (OR: 2.576, p < 0.05), and leg LM (OR: 2.088, p < 0.05) predicted casualty drag success. Upper body power (OR: 3.910, p < 0.05), absolute trunk LM (OR: 2.387, p < 0.05), leg LM (OR: 2.290, p < 0.05), and total LM (OR: 1.830, p < 0.05) predicted maximum single lift success. Relative and absolute arm LM (OR: 3.488-7.377, p < 0.05), leg LM (OR: 1.965, p < 0.05), and upper body power (OR: 1.957, p < 0.05) predicted water can carry success. %BF (OR: 0.814, p = 0.007), V̇O2peak (OR: 1.160, p = 0.031), and lower body strength (OR: 1.059, p < 0.001) predicted repeated lift and carry success. V̇O2peak (OR: 1.540, p < 0.001) predicted 2-km ruck march success. Modifiable characteristics were the strongest predictors for GCC-based PES task success to warrant their improvement for enhancing PES performance for women.

Characterising the physical demands of critical tasks across the Royal Australian Air Force

BACKGROUND

Militaries have historically utilised generic physical fitness tests to assess physical readiness, but there has been a recent shift to develop physical employment standards (PES) based on actual job demands.

OBJECTIVE

The purpose of this investigation was to characterise the physical demands of critical tasks performed by Royal Australian Air Force (RAAF) personnel to inform PES development.

METHODS

Job task analysis were performed for 27 RAAF trades. Criterion tasks were identified through a systematic approach involving workshops and field-observations. The identified tasks were assessed for dominant physical capacity and grouped into movement-based clusters. Psychophysiological measures were collected from personnel performing the tasks.

RESULTS

Of 87 criterion tasks, 92% were characterised as manual handling dominant. Across these 87 tasks the principal physical capacities were: muscular strength (59%), muscular endurance (52%) and cardiorespiratory endurance (39%). The most common movement clusters were Lift to Platform (44%) and Lift and Carry (38%). Lift to Platform tasks required lifting to a median height of 1.32 m (1.20 -1.65 m) and a median mass of 25.0 kg (21.0 -28.9 kg) per person. Median carry mass was 25.0 kg (22.4 -36.1 kg) per person and distance was 26.0 m (17.5 -50.0 m). Median task mean 'Vdot;O2, HR and RPE were 1.8 L.min- 1 (1.5-2.2 L.min- 1), 137 b.min- 1 (120-144) and 13 (12-14).

CONCLUSIONS

The high proportion of manual handling criterion tasks emphasises the importance of these activities and the underlying physical capacities for RAAF personnel. Current fitness assessments are unlikely to predict job task performance.

Profiling injuries sustained following implementation of a progressive load carriage program in United States marine corps recruit training

BACKGROUND

Load carriage tasks during United States Marine Corps (USMC) recruit training can cause injury. Load carriage conditioning, if optimized, can reduce injury risk.

OBJECTIVE

To compare injuries sustained by USMC recruits following participation in either the Original Load Carriage (OLC) program or a Modified Load Carriage (MLC) program.

METHODS

Retrospective musculoskeletal injury data were drawn from the USMC San Diego Sports Medicine injury database for recruits completing the OLC (n = 2,363) and MLC (n = 681) programs. Data were expressed as descriptive statistics and a population estimate of the OLC:MLC relative risk ratio (RR) was calculated.

RESULTS

The proportion of injuries sustained in the MLC cohort (n = 268; 39% : OLC cohort, n = 1,372 : 58%) was lower, as was the RR (0.68, 95% CI 0.61- 0.75). The leading nature of injury for both cohorts was sprains and strains (OLC n = 396, 29%; MLC n = 66; 25%). Stress reactions were proportionally higher in MLC (n = 17, 6%; OLC n = 4, 0.3%), while stress fractures were proportionately lower (MLC n = 9, 3%; OLC n = 114, 8%). Overuse injuries were lower in MLC (- 7%). The knee, lower leg, ankle, and foot were the top four bodily sites of injuries and the Small Unit Leadership Evaluation (SULE), Crucible, overuse-nonspecific, running, and conditioning hikes were within the top five most common events causing injury. The prevalence rates of moderate severity injury were similar (MLC = 23%; OLC = 24%), although MLC presented both a higher proportion and prevalence of severe injuries (MLC = 6%; OLC = 3%, respectively).

CONCLUSION

A periodized load carriage program concurrently increased exposure to load carriage hikes while reducing injuries both during the load carriage hikes and overall.

Association of clinically-measured and dynamic ankle dorsiflexion assessed by markerless motion capture during the drop-jump task on landing biomechanics and risk of ankle injury in military personnel undergoing 10 weeks of physical training

OBJECTIVES

Determine the influence of clinically-measured maximum dorsiflexion, dynamic peak dorsiflexion and percent of clinically-measured maximum dorsiflexion used during a drop-jump task on landing biomechanics and risk of ankle injury in military personnel.

DESIGN

Prospective cohort study.

METHODS

672 participants (122 women) enrolled. The weightbearing lunge test assessed clinically-measured maximum dorsiflexion averaged across limbs (degrees). Markerless motion capture and force plates collected lower extremity kinematic and kinetic data during a drop-jump task. Percent of clinically-measured maximum dorsiflexion used during landing was calculated as dynamic peak dorsiflexion divided by clinically-measured value, multiplied by 100 (%). De-identified injury data was derived from military physical therapists. Simple linear regression analysis determined the association between dorsiflexion measures and landing biomechanics. Simple binary logistic regression analyses identified predictors of ankle injuries. Statistical significance was set at α = 0.05.

RESULTS

Eighteen participants sustained a traumatic ankle injury from a landing. All measures of dorsiflexion were associated with movement patterns that countered the stiff-legged landing strategy with dynamic measures showing a higher predictive value. Protective factors against ankle injury included height (odds ratio: 0.818, p = 0.006) and weight (odds ratio: 0.824, p = 0.023) for women. Relative braking impulse was a risk factor for men (odds ratio: 1.890, p = 0.001).

CONCLUSIONS

Greater clinically-measured and dynamic measures of dorsiflexion were associated with movement patterns that countered the stiff-legged landing strategy but neither measure of dorsiflexion predicted ankle injury risk. Resultant biomechanics and anthropometrics influenced ankle injury risk to warrant recognition for injury prevention initiatives.

Comparison of In-service Reduced vs. Full Torso Coverage Armor for Females

INTRODUCTION

Body armor and torso-borne equipment are critical to the survivability and operational effectiveness of a soldier. Historically, in-service designs have been predominantly designed for males or unisex, which may be disadvantageous for females who are shaped differently and, on average, smaller in stature and mass than their male counterparts. This study assesses the biomechanical and performance impact of two Canadian in-service armors and fighting load conditions on females.

MATERIALS AND METHODS

Four tasks (i.e., range of motion, treadmill march [×2], and a wall obstacle) were performed in a Baseline condition and two in-service torso-borne equipment conditions; the full torso coverage (FTC) condition has full upper torso soft armor with the fighting load carried in a separate vest, while the reduced coverage (RC) has a plate carrier with fighting load integrated into the armor carrier, bulk positioned higher, and less torso coverage. Both used identical combat loads and front and back armor plates. Trunk range of motion, march lower limb kinematics, march shoulder and hip skin pressures, perceived discomfort after the march, and time to traverse a wall obstacle were captured. Data were collected to assess the biomechanics and usability of the systems for eight females, representative of military recruits. Linear mixed-effects models were created, and analysis of variances (ANOVAs) were then performed on all the outcome measures (P < .05). Tukey's post-hoc procedures were performed when appropriate (P < .05).

RESULTS

There were significant differences between the RC and FTC for the sit and reach test (P < .001), lateral bend test (P < .001), and wall traverse time (P < .01). In all cases, the RC outperformed FTC. There were no differences between the two in-service conditions with respect to hip, knee, and ankle flexion/extension. The RC average skin pressure was higher than the FTC at the left and right shoulders by 103% and 79%, respectively, and peak skin pressure at the left shoulder by 75%. Both in-service conditions showed decrements in performance from Baseline for sit and reach (P < .001), lateral bend (P < .001), and peak hip and knee flexion (P < .01) with the FTC showing decreases in trunk rotation (P < .001) and wall traverse time (P < .01).

CONCLUSIONS

Improved outcomes for the RC can be attributed to design differences. The lower placement of bulk in FTC may act as a physical barrier during range of motion tasks and the wall obstacle. The presence of shoulder caps on FTC provides another physical barrier that likely impedes full movement through the arms and shoulders. While the narrower shoulder straps of the RC remove the barrier, it causes more concentrated skin pressures on the shoulder that can lead to injury. The results suggest that the RC offers a potential for increased operational effectiveness in females (and potentially for males) compared to the FTC system. Shoulder pressure, an important predictor of discomfort and injury, is the only measure for which FTC outperformed the RC. Future torso-borne equipment designs targeting this outcome measure could help increase the effectiveness of the RC and other similar systems that reduce torso coverage, though survivability implications must also be considered.

Effects of Occupational Load on the Acceleration, Change of Direction Speed, and Anaerobic Power of Police Officers

ABSTRACT

Kukić, F, Janković, R, Dawes, JJ, Orr, R, and Koropanovski, N. Effects of occupational load on the acceleration, change of direction speed, and anaerobic power of police officers. J Strength Cond Res XX(X): 000-000, 2022-Police officers engage in movements such as foot pursuits, sudden directional changes, or prolonged sprinting while wearing occupational loads (including body armor, baton, radio, handcuffs, and sidearm). This study investigated the effects of incrementally heavier loads carried by police students on their physical performance. Police students (n = 63; male n = 39 male and 24 female students) performed an acceleration over a 10-m distance (Acc10m), Illinois agility test (IAT), and 300-yard shuttle run test (ShR300y) without load, with a 5-kg load (handgun, spare empty magazine, baton, and handcuffs), and with a 10-kg load (loaded vest). The effects of different load conditions were investigated for both sexes using a repeated-measure analysis of variance and Cohen's effect size. Female students carried relatively heavier loads and were slower than male students in Acc10m, IAT, and ShR300y. Load significantly (p < 0.001) impaired the performance in Acc10m, IAT, and ShR300y in both sexes, but the effects were greater (p < 0.001) among female police students. A load as little as 5 kg was sufficient to reduce Acc10m, IAT, and ShR300y among police students. Increasing the load to 10 kg (i.e., wearing the body armor) did not significantly affect Acc10m and IAT among male students, but it did affect Acc10m and IAT among female students. Sprint endurance (i.e., ShR300y) was strongly affected by both loads regardless of sex. Strength and conditioning programs should focus on strength, power, and anaerobic endurance to improve performance while carrying occupational loads. Occasional training with loads similar to those at work may further ensure that officers are fit for purpose.

Effects of Load Carriage on Postural Control and Spatiotemporal Gait Parameters during Level and Uphill Walking

Load carriage and uphill walking are conditions that either individually or in combination can compromise postural control and gait eliciting several musculoskeletal low back and lower limb injuries. The objectives of this study were to investigate postural control responses and spatiotemporal parameters of gait during level and uphill unloaded (UL), back-loaded (BL), and front-loaded (FL) walking. Postural control was assessed in 30 asymptomatic individuals by simultaneously recording (i) EMG activity of neck, thoracic and lumbar erector spinae, and rectus abdominis, (ii) projected 95% ellipse area as well as the anteroposterior and mediolateral trunk displacement, and (iii) spatiotemporal gait parameters (stride/step length and cadence). Measurements were performed during level (0%) and uphill (5, 10, and 15%) walking at a speed of 5 km h^-1 without and with a suspended front pack or a backpack weighing 15% of each participant's body weight. The results of our study showed that postural control, as indicated by increased erector spinae EMG activity and changes in spatiotemporal parameters of gait that manifested with decreased stride/step length and increased cadence, is compromised particularly during level and uphill FL walking as opposed to BL or UL walking, potentially increasing the risk of musculoskeletal and fall-related injuries.

Core and Whole-Body Vibration Exercise Improve Military Foot March Performance in Novice Trainees: A Randomized Controlled Trial

INTRODUCTION

The purpose of the present study was to investigate core exercise training and whole-body vibration (WBV) as a training method to improve performance and recovery from an 8-km military foot march in novice trainees.

MATERIALS AND METHODS

A 3 × 5 repeated measures randomized control trial was used to evaluate the effects of core exercise training and WBV on performance and recovery from an 8-km foot march. Thirty-nine participants were randomized into three groups: core exercise (Ex), WBV with core exercise (WBVEx), and control. Each participant completed two 8-km foot marches (FM1 and FM2) with a 35 pound rucksack, separated by 4 weeks. Participants in the Ex and WBVEx groups completed 3 weeks of core exercise training, three times per week in between FM1 and FM2. Performance time, creatine kinase (CK), and interleukin-6 (IL-6) were measured. The Auburn University Institutional Review Board approved all aspects of this study (protocol number: 19-211 MR 1907).

RESULTS

Performance time (P < .001) and CK (P = .005) were significantly improved during FM2 as compared to FM1. The Ex (d = -0.295) and WBVEx (d = -0.645) treatments had a large effect on performance time. CK (P < .001) and IL-6 (P < .001) were significantly elevated at the completion of the foot march regardless of group. Only CK remained elevated for 2 days (P < .001) following the foot march.

CONCLUSIONS

Core exercise training with or without WBV improved 8-km foot march performance time by 5-6 minutes. The improvements are likely because of an increase in trunk stability. Additionally, this study showed that completing two identical foot marches a month apart increases performance and improves recovery.

Effects of load carriage on measures of postural sway in healthy, young adults: A systematic review and meta-analysis

Load carriage (LC) is a contributing factor to musculoskeletal injury in many occupations. Given that falls are a common mechanism of injury for those frequently engaging in LC, understanding the effects of LC on postural stability (PS) is necessary. A systematic review and meta-analysis was conducted to examine effects of LC on PS. Sixteen and 9 studies were included in the qualitative and quantitative synthesis, respectively. In most studies, it was found that LC leads to a decrease in PS with significant effects on center of pressure (COP) sway area (standardized mean difference = 0.45; p < 0.005) and COP anterior-posterior excursion (standardized mean difference = 0.52; p < 0.05). Furthermore, load magnitude and load placement are factors which can significantly affect COP measures of PS. It is recommended to minimize load magnitude and equally distribute load when possible to minimize LC effects on PS. Future research should examine additional factors contributing to differences in individual PS responses to LC such as changes in muscle activation and prior LC experience.

Load Carriage and Physical Exertion Influence Soldier Emotional Responses

INTRODUCTION

Regular aerobic exercise benefits psychological health, enhancing mood in clinical and nonclinical populations. However, single bouts of exercise exert both positive and negative effects on emotion. Exercise reliably increases emotional arousal. Its effects on emotional valence are thought to depend on an interplay between cognitive and interoceptive factors that change as a function of exercise intensity, as studied in clinical, healthy, and athlete populations. However, special populations, such as military, first responders, and endurance athletes, have unique physical exertion requirements that can coincide with additional cognitive, physical, and environmental stressors not typical of the general population. Load carriage is one such activity. The present study examined emotional valence and arousal during sustained, heavy load carriage akin to military training and operations.

METHODS

Thirteen (one woman) active duty soldiers completed a V̇O2max test, a 2-h loaded (up to 50% body mass) and unloaded (empty rucksack) treadmill foot march (3 mph/4% incline) on separate days, during which they rated their exertion and emotional valence and arousal every 40 min. They also completed measures of positive and negative affect and anxiety before and every 20 min after the foot march.

RESULTS

Two hours of loaded foot march led to elevated perceived exertion and less positive, more negative and anxious feelings. Higher rated exertion and more negative emotion were associated with higher percent HRmax and V̇O2peak at multiple time points.

CONCLUSIONS

These results support affect exertion models such as the Dual Mode Theory, whereby physical exertion becomes less pleasant with increasing intensity, and provide insights into how affective responses applied contexts may help predict time to fatigue or failure.

Biomechanical and physiological effects of female soldier load carriage: A scoping review

Loads carried by military populations can affect those of smaller stature, such as the average female, due to the higher percentage of body weight the loads represent. Despite this, most load carriage research is performed on males. Peer reviewed articles were collected from four databases to summarize available research on biomechanical and physiological effects of load carriage on females in the military. Extraction and thematic analysis were performed on 18 articles. 39% looked at biomechanical differences between loads in females, 61% looked at how the same load affected males and females, 44% looked at sex-by-load interaction effects, and 72% discussed impacts of load on females. The research revealed that military load carriage affects the biomechanics and physiology differently in females and to a greater extent than in males. Several gaps in available literature were found. Very few studies used military participants, military equipment, and/or employed occupationally relevant data collection methodologies.

The Effects of Early Physiotherapy Treatment on Musculoskeletal Injury Outcomes in Military Personnel: A Narrative Review

The risks and incidence rates of musculoskeletal injuries among military personnel are high, and the importance of physiotherapy in treating these injuries is well established. However, what is less clear is whether the timing of commencement of physiotherapy treatment affects musculoskeletal injury outcomes in military personnel. This lack of clarity is exacerbated by the known underreporting of injuries among military personnel, and the resulting self-management of musculoskeletal injuries using analgesics, non-steroidal anti-inflammatories and other means. This narrative review was designed to identify and synthesize current evidence regarding the effects of timing of physiotherapy treatment on musculoskeletal injury outcomes, focusing on potential benefits of early versus typical or delayed commencement of physiotherapy treatment. Overall, current evidence suggests early physiotherapy treatment of musculoskeletal injuries offers distinct advantages over typical or delayed commencement of physiotherapy treatment in military settings. Specifically, it appears early treatment expedites recovery in early phases following injury onset and benefits longer term mental health and well-being. It may also reduce the need for more invasive and costly health care interventions and enable earlier return to training and operational service. Importantly, a cultural shift within military contexts to ensure early reporting of musculoskeletal injuries is required if the benefits of early commencement of physiotherapy treatment are to be achieved.

The Impact of Footwear on Occupational Task Performance and Musculoskeletal Injury Risk: A Scoping Review to Inform Tactical Footwear

The aim of this scoping review was to investigate the impact of footwear on worker physical task performance and injury risk. The review was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews protocol and registered in the Open Science Framework. Key search terms were entered into five academic databases. Following a dedicated screening process and critical appraisal, data from the final articles informing this review were extracted, tabulated, and synthesised. Of 19,614 identified articles, 50 articles informed this review. Representing 16 countries, the most common populations investigated were military and firefighter populations, but a wide range of general occupations (e.g., shipping, mining, hairdressing, and healthcare workers) were represented. Footwear types included work safety boots/shoes (e.g., industrial, gumboots, steel capped, etc.), military and firefighter boots, sports shoes (trainers, tennis, basketball, etc.) and various other types (e.g., sandals, etc.). Occupational footwear was found to impact gait and angular velocities, joint ranges of motion, posture and balance, physiological measures (like aerobic capacity, heart rates, temperatures, etc.), muscle activity, and selected occupational tasks. Occupational footwear associated with injuries included boots, conventional running shoes, shoes with inserts, harder/stiffer outsoles or thin soles, and shoes with low comfort scores-although the findings were mixed. Occupational footwear was also linked to potentially causing injuries directly (e.g., musculoskeletal injuries) as well as leading to mechanisms associated with causing injuries (like tripping and slipping).

Can training trunk musculature influence musculoskeletal pain and physical performance in military police officers?

To investigate the effect of a Trunk Training (TT) program on the general musculoskeletal pain (GMP) and physical performance of Military Police Officers. Twenty officers were divided into either control group (CG) or TT group (TTG). Both groups performed nine weeks of traditional physical training. However, the TTG had 25-minutes allocated to TT during each scheduled physical training period. Anthropometric, trunk endurance, and physical fitness tests were completed pre- and post-training for both groups. Both groups also answered a weekly questionnaire about their GMP. Post-training, trunk endurance performance was significantly higher (p < 0.05) and the GMP significantly lower (p < 0.05) in the TTG when compared to the CG. Improvement in side plank test scores was associated with a decreased in GMP (r = -0.495, p < 0.05). TT can reduce the perception of GMP in addition to increasing the endurance of the trunk muscles. The side plank was the only physical test associated with GMP. Practitioner summary: Trunk Training can reduce general musculoskeletal pain and increase the endurance of the trunk muscles without a concomitant loss in general fitness in elite Military Police Officers. This research lasted 11 weeks and presents real-world and pragmatic findings.

The Use of Fitness Testing to Predict Occupational Performance in Tactical Personnel: A Critical Review

Tactical personnel work in an occupation that involves tasks requiring a high level of cardiovascular fitness as well as muscular strength and endurance. The aim of this literature review was to identify and critique studies investigating the relationship between physical fitness, quantified by fitness assessment measures, and occupational task performance. Databases were searched for relevant articles which assessed a fitness measure and a measure of occupational performance. A total of 15 articles were included and were deemed to be of acceptable methodological quality (8.4/12 on the Critical Appraisal Skills Programme checklist). Included articles assessed a variety of fitness attributes and occupational tasks. Across tactical groups, there appear to be no standardized fitness tests that can determine occupational performance, with aerobic fitness, anaerobic fitness, strength, endurance, power, and agility all being associated with occupational task performance. A wide range of fitness assessments appears to be required to predict occupational performance within tactical personnel. Efforts should be made to base fitness assessments on occupational demands unique to both the environment and requirements of each individual tactical unit.