Load Carriage System Research Articles

Effects of Armor Design and Marksmanship Posture on Performance, Postural Sway and Perceived Workload During a Military Rifle Marksmanship Task.

This study investigated the effects of mass and vertical center-of-mass position of combat items attached to a tactical vest, as well as marksmanship posture on rifle marksmanship performance, postural sway, and perceived workload during a simulated rifle shooting task. A tactical vest serves as a load carriage system in addition to providing body protection. Its design, particularly the mass and vertical position of attached combat items, may impact postural control during rifle shooting and thus marksmanship performance. Thirty-two participants performed a simulated rifle shooting task on a force plate with a tactical vest on. Three independent variables were considered: load mass (4 levels), vertical load center-of-mass position (4 levels), and marksmanship posture (2 levels). The dependent variables were: 6 rifle marksmanship performance measures, 7 postural sway measures, and a perceived workload measure. Heavier load mass significantly degraded rifle marksmanship performance, and increased postural sway and perceived workload. Marksmanship posture significantly affected rifle marksmanship performance and postural sway. The kneeling posture resulted in less postural sway and better marksmanship performance than the standing posture. Vertical load center-of-mass position affected only part of the marksmanship performance measures and did not affect the measures of postural sway and perceived workload. Reducing combat item mass on tactical vests and enhancing soldier postural control ability would improve rifle marksmanship and soldier lethality. The study findings inform the development of future military tactical vests and rifle marksmanship training, highlighting the need for lightweight gear design and postural control training.

Altered trunk-pelvis kinematics during load carriage with a compliant versus a rigid system

Load carriage is a key component of hiking and military activity. The design of the load carriage system (LCS) could influence performance and injury risk. This study aimed to compare a traditional and a compliant LCS during walking and a step-up task to quantify differences in oxygen consumption and trunk-pelvis kinematics. Fourteen participants completed the tasks whilst carrying 16 kg in a rigid and a compliant LCS. There were no differences in oxygen consumption between conditions during either task (p > 0.05). There was significantly greater trunk-pelvis axial rotation (p = 0.041) and lateral flexion (p = 0.001) range of motion when carrying the compliant LCS during walking, and significantly greater trunk-pelvis lateral flexion range of motion during the step-up task (p = 0.003). Carrying 16 kg in a compliant load carriage system results in greater lateral flexion range of motion than a traditional, rigid system, without influencing oxygen uptake.

Analytical parameters to check association between load carriage system and bag packs-influenced musculoskeletal complications among school going students: a scoping review.

This study aimed to investigate the correlation between load-carriage systems and backpacks on musculoskeletal complications among school-going students. Additionally, the purpose was to identify research gaps and provide recommendations for future research. To conduct this study, we conducted a thorough search of five databases for literature published between January 2010 and December 2022. Our focus was on original published articles that reported musculoskeletal complications using analytical parameters or outcome measures among school-going students. Two reviewers independently extracted data for eligibility. The studies selected for the analysis focused on musculoskeletal complications and the outcome measures to report these complications. A total of 3541 titles were screened; of which, 18 observational studies were included. The musculoskeletal complications identified in these studies included lower back, shoulder, and neck pain and disturbed posture. Overall, the quality of the reporting in these studies was deemed satisfactory. Our analysis revealed that pain and postural abnormalities were the most frequently reported complications. Hence, we recommend that future studies incorporate multiple evaluations rather than concentrating on a single symptom.

Common law enforcement load carriage systems have limited acute effects on postural stability and muscle activity

Law enforcement officers are inherently at a high risk of injury and the loads they must carry during their occupational duties further increase their injury risk. It is unknown how different methods of carrying a law enforcement officer's load influence factors related to injury risk. This study assessed the effects of common law enforcement load carriage systems on muscular activity and postural stability while standing. Twenty-four participants performed single and dual-task (i.e. concurrent performance of cognitive tasks) standing while wearing a duty belt, tactical vest, and no load. The postural stability and muscle activity were measured and effects of condition and task examined. Dual task standing decreased postural stability and increased muscular activity. The belt and vest (7.2 kg each) increased muscle activity compared to control for the right abdominals, low back, right thigh. The duty belt resulted in less muscle activity in the right abdominals but more muscle activity in the left multifidus compared to the control. The findings indicate that common law enforcement load carriage systems increase muscular activity but do not affect postural stability. However, the lack of differences between the duty belt and tactical vest did not provide clear support for one load carriage system versus the other.

Impact of Backpacks on Ergonomics: Biomechanical and Physiological Effects: A Narrative Review.

(1) Background: the effects of load carriage packs on human gait biomechanics, physiology and metabolism depend on the weight carried, the design of the pack and its interaction with the user. (2) Methods: An extensive search in the PubMed database was performed to find all the relevant articles using the following keywords: backpack, rucksack, backpack ergonomy and sports backpack; 60 articles were included. (3) Results and significance: Double pack (DP) and T-pack (TP) designs are recommended solutions for school children, compared with backpacks (BP). For soldiers and hikers, a backpack remains the best compromise. A hip belt is recommended for BPs as well as for the back of DPs. Shorter and stiffer shoulder straps combined with a higher and tighter load placement on the back provide the best combination in terms of balance, muscle activation and energy expenditure. It is, therefore, possible to determine guidelines for designing the optimal load carriage system, depending on the application. (4) Conclusions: based on the available evidence, DP and TP are advantageous in terms of posture. DP is better than conventional BPs in terms of balance and muscle activation, but has the disadvantage of limited visibility, thermal sensation and obstructed ventilation. In general, it is desirable not to exceed 40% of body mass (BM).

Multiday load carriage decreases ability to mitigate ground reaction force through reduction of ankle torque production

The aim of this study was to examine the impact of backpack load carriage on lower limb strength and loading rate change in a cohort that match military recruit profiles. Twenty-six participants walked on a treadmill either carrying a military load carriage system (32 kg) or unloaded for 2 h on two consecutive days. Participants ground reaction forces and strength measures were assessed using a force platform and dynamometry, respectively. Testing included assessments before and after treadmill walking on days one and two, and 24 h following day 2. When assessed by mixed methods ANOVA (alpha: 0.05) statistically significant interaction effects were observed for loading peak (p = 0.031), loading rate (p = 0.035) and plantarflexor torque dynamometry variables at 60°s−1 (p = 0.011) and 120°s−1 (p = 0.024). Repeated measures correlation highlighted associations between plantarflexor torque at 60°s−1 and loading rate (r = −0.901, p < 0.001). Load carriage reduced lower limb torque which did not recover between days. Plantarflexor torque reductions were associated with increases in loading rate. Practitioners should consider that load bearers are more likely to experience lower limb injury during multi-day load carriage. Future work should develop protocols to reduce plantarflexor torque loss in order to reduce ground reaction force change.

Is skin pressure in load carriage over-evaluated?

Skin pressure is a biomechanical measure widely used in the assessment of load carriage systems. However, because of the complicated contour of human body, the stiffness of the pressure sensor array, and the large range of measurable pressures, there is much variability in previously reported results. In this paper, a simple mechanical model for load carriage was proposed, and the skin pressures beneath the shoulder and hip straps were predicted from the strap forces based on Laplace’s law. The proposed model was used to analyze data from literature with an aim to check the reliability of existing pressure measurements. The static and dynamic pressures at five locations on eight subjects wearing a backpack with a 10 kg load, while standing and walking on a treadmill, were measured respectively using pressure sensors of the air pack type. The combination of literature data analysis and experimental testing proved that the existing measurement method of interface pressure in load carriage systems often leads to over-estimation and this might misguide the pressure criteria set for load carriage system usage and design. The proposed model will be useful for quick prediction of the interface pressure in load carriage systems.

Design and Analysis of Lightweight Lower Limb Exoskeleton for Military Usage

Abstract: Nowadays, due to technological advancement, weapons are becoming smaller in size, which leads to the number of weapons carried by a single person increasing. As the number of weapons is increasing, then the capacity of the load carriage system of military personnel causes a great energy loss to carry weight. Also, carrying a weight of about 25 kg to 50 kg in different terrain causes different foot injuries which create a strain on the human body. An exoskeleton is a device used to replicate the motion of the human body so that humans can be used to control mechanical power for working on different operations which are beyond human strength. The exoskeleton technology makes it possible to reduce the energy loss of military personnel to produce controlled motion of the exoskeleton in different terrain. Hence, this project is aims to design a lower limb exoskeleton for carrying military load carriage systems. The designing and simulating the lower limb exoskeleton is done on fusion 360. Keywords: lower limb exoskeleton, military exoskeleton, exoskeleton design, exoskeleton analysis

Gait and neuromuscular dynamics during level and uphill walking carrying military loads

ABSTRACT The neuromuscular system responds to perturbation and increasing locomotor task difficulty by altering the stability of neuromuscular output signals. The purpose of this study was to determine the effects of two different military load carriage systems on the dynamic stability of gait and muscle activation signals. 14 army office cadets (20 ± 1 years) performed 4-minute treadmill walking trials on level (0%) and uphill (10%) gradients while unloaded, and with 11 kg backpack and 11 kg webbing loads while the activity of 6 leg and trunk muscles and the motion of the centre of mass (COM) were recorded. Loaded and uphill walking decreased stability and increased magnitude of muscle activations compared to loaded and level gradient walking. Backpack loads increased the medio-lateral stability of COM and uphill walking decreased stability of vertical COM motion and increased stride time variability. However, there was no difference between the two load carriage systems for any variable. The reduced stability of muscle activations in loaded and uphill conditions indicates an impaired ability of the neuromuscular control systems to accommodate perturbations in these conditions which may have implications on the operational performance of military personnel. However, improved medio-lateral stability in backpack conditions may indicate that participants were able to compensate for the loads used in this study, despite the decreased vertical stability and increased stride time variability evident in uphill walking. This study did not find differences between load carriage systems however, specific load carriage system effects may be elicited by greater load carriage masses.

A fit and function analysis of the UK OSPREY body armour system for female users

IntroductionOSPREY personal armour has been issued to UK forces since 2005. From 2015, the VIRTUS personal armour and load carriage system have been progressively replacing OSPREY. In 2016, the ban...

Determining the optimum anatomical coverage of side plates for the VIRTUS body armour and load carriage system

IntroductionSide plates are worn by UK Armed Forces as part of the VIRTUS body armour and load carriage systems to protect the thorax and abdomen from high-velocity threats. The VIRTUS...

Sizing of ballistic arm protection for the VIRTUS body armour and load carriage system

IntroductionSevere haemorrhage from the arm that is unresponsive to direct pressure necessitates the application of a tourniquet. Detachable arm protection, referred to as brassards, are used by the UK Armed...

Design of a load carriage system oriented to reduce acceleration forces when carrying a backpack

In military life, load carriage is an unavoidable part of field operations which is the reason why soldiers often make use of a military backpack. Infantry soldiers usually carry loads weighting more than 30% of their body weight. When the soldier carries a certain weight, his energy expenditure increases, which causes a reduction in performance. The transported load has a movement similar to the vertical displacement of the center of mass of the soldier while walking. This leads to a significant increase in the acceleration forces generated by the action of said load on the body which explains the increase in energy expenditure. The objective of this project was to develop a load carriage system that suspends the load and reduces its vertical displacement. Results show a reduction in both the vertical excursion of the load and in the total vertical ground reaction force when carrying a load with the developed prototype, with respect to the conventional military backpack.

Biomechanical Modelling Of Head-Head Load Carriage And Neuromuscular Control Of The Neck During Level Walking

Head load carriage is a common phenomenon in some parts of the world. This is prevalent across sub-Saharan Africa where women and children are used as pedestrian load-transporters. It has also been observed that during gymnasium and a few sporting activities, experienced gymnasts carry loads or other gymnasts by placing them their heads. The neck plays a major role in supporting the head in balance while generating the controlled head movements that are essential for balance in the head load carriage. Hence in this study, a biomechanical model of the controlled human head-head load carriage system is developed. The biomechanics model of the head loading problem in this study is a type of constrained mechanical three-dimensional, matrix coefficients, multibody systems which arise in many applications like robotics, vehicle and machinery dynamics. This governing equation was solved using Differential Transform Method (DTM) and was validated with the fourth order Runge-Kutta numerical method (RK4). Good agreements are reached between the two solutions. The effects of head mass, head load, neck mass were investigated. Other effects such as upper and lower linkage lengths were investigated in the study. As the head load increases, there were increases in both axial and angular displacement of the head and the neck motion.

Design, model, and performance evaluation of a biomechanical energy harvesting backpack

Abstract Introducing compliant elements to backpack structures has been shown to reduce both the peak forces experienced by the user and the metabolic cost of walking. In previous work, we developed a novel load carriage system that allowed weight carried in a backpack to oscillate in the medial-lateral direction. In this paper, we introduce a new energy harvesting module, to be added to the load carriage module, that generates electricity from the movement of the carried mass. The energy harvesting module is implemented for two outcomes: to generate electricity for powering portable electronics and to effectively modulate oscillation amplitude and phase of the carried mass in the load carriage system. This paper outlines the design, model, and performance evaluation of our novel energy harvesting device. First, a model was developed so that we may determine device parameters that result in desired device behaviour. Then, the model was evaluated using a combination of bench top experiments and human walking experiments to validate its predictive capabilities. Testing revealed that the model can be used to predict general device behaviour, but could be further developed to improve accuracy. Lastly, we evaluated device performance in human walking experiments. The energy harvesting device generated up to 0.22 ± 0.08 W of electrical power while walking. Walking with the device while generating electricity did not significantly increase user effort, compared to walking with the weight rigidly fixed.

Generating electricity while walking with a medial-lateral oscillating load carriage device.

Biomechanical energy harvesters generate electricity, from human movement, to power portable electronics. We developed an energy harvesting module to be used in conjunction with a load carriage device that allows carried mass in a backpack to oscillate in the medial–lateral (M–L) direction. The energy harvesting module was designed to tune M–L oscillations of the carried mass to create favourable device–user interaction. We tested seven energy harvesting conditions and compared them to walking with the device when the weight was rigidly fixed to the backpack frame. For each energy harvesting condition, we changed the external load resistance: altering how much electricity was being generated and how much the carried mass would oscillate. We then correlated device behaviour to the biomechanical response of the user. The energy harvesting load carriage system generated electricity with no significant increase in the metabolic power required to walk, when compared to walking with the carried weight rigidly fixed. The device was able to generate up to 0.22 ± 0.03 W of electricity, while walking with 9 kg of carried weight. The device also reduced the interaction forces experienced by the user, in the M–L direction, compared to walking with the device when the mass was rigidly fixed.

Duty belt or load-bearing vest? Discomfort and pressure distribution for police driving standard fleet vehicles

Police working in active duty have a high prevalence of musculoskeletal pain, with lower back pain being the most frequently reported. As a part of uniform regulations, Swedish police are mandated to wear body armour and duty belts at all times during work. This study aimed to investigate the effect of different load carriage designs on invehicle sitting pressure and self-rated discomfort among police. Results showed less discomfort when wearing the alternate load carriage system incorporating a load-bearing vest and thigh holster compared to the standard load carriage system consisting of a duty belt. Pressures in the lower back were reduced when wearing the load-bearing vest whereas pressures in the upper back region increased. Relocating appointments away from the waist has the potential to improve sitting positions and the ergonomic situation for police when driving fleet vehicles.

The energetic consequences of wearing a belt-supported armored vest during overground hiking

Purpose: Load carriage for military ground troops on patrol can include a rifle, operational kit, a loaded backpack, and an armored vest, such as the modular tactical vest (MTV) used in this study. As the total mass of transport increases, so too does the potential for fatigue and injuries. Thus, finding the most economical and comfortable load carriage system may allow troops to perform their duties in the safest and most effective manner. The purpose of this study was to assess the energetic and cardiovascular effects of using an MTV with a backpack-style hip belt during overground hiking. It was hypothesized that both energetic and cardiovascular demands of overground hiking with an MTV would improve with the use of the hip belt.

Validation of an instrumented dummy to assess mechanical aspects of discomfort during load carriage.

Due to the increasing load in backpacks and other load carriage systems over the last decades, load carriage system designs have to be adapted accordingly to minimize discomfort and to reduce the risk of injury. As subject studies are labor-intensive and include further challenges such as intra-subject and inter-subject variability, we aimed to validate an instrumented dummy as an objective laboratory tool to assess the mechanical aspects of discomfort. The validation of the instrumented dummy was conducted by comparison with a recent subject study. The mechanical parameters that characterize the static and dynamic interaction between backpack and body during different backpack settings were compared. The second aim was to investigate whether high predictive power (coefficient of determination R2>0.5) in assessing the discomfort of load carriage systems could be reached using the instrumented dummy. Measurements were conducted under static conditions, simulating upright standing, and dynamic conditions, simulating level walking. Twelve different configurations of a typical load carriage system, a commercially available backpack with a hip belt, were assessed. The mechanical parameters were measured in the shoulder and the hip region of the dummy and consisted of average pressure, peak pressure, strap force and relative motion between the system and the body. The twelve configurations consisted of three different weights (15kg, 20kg, and 25kg), combined with four different hip belt tensions (30N, 60N, 90N, and 120N). Through the significant (p<0.05) correlation of the mechanical parameters measured on the dummy with the corresponding values of the subject study, the dummy was validated for all static measurements and for dynamic measurements in the hip region to accurately simulate the interaction between the human body and the load carriage system. Multiple linear regressions with the mechanical parameters measured on the dummy as independent variables and the corresponding subjective discomfort scores from the subject study as the dependent variable revealed a high predictive power of the instrumented dummy. The dummy can explain 75% or more of the variance in discomfort using average pressures as predictors and even 79% or more of the variance in discomfort using strap forces as predictors. Use of the dummy enables objective, fast, and iterative assessments of load carriage systems and therefore reduces the need for labor-intensive subject studies in order to decrease the mechanical aspects of discomfort during load carriage.

Effects of thigh holster use on kinematics and kinetics of active duty police officers

BackgroundBody armour, duty belts and belt mounted holsters are standard equipment used by the Swedish police and have been shown to affect performance of police specific tasks, to decrease mobility and to potentially influence back pain. This study aimed to investigate the effects on gait kinematics and kinetics associated with use of an alternate load carriage system incorporating a thigh holster. MethodsKinematic, kinetic and temporospatial data were collected using three dimensional gait analysis. Walking tests were conducted with nineteen active duty police officers under three different load carriage conditions: a) body armour and duty belt, b) load bearing vest, body armour and thigh holster and c) no equipment (control). FindingsNo significant differences between testing conditions were found for temporospatial parameters. Range of trunk rotation was reduced for both load carriage conditions compared to the control condition (p<0.017). Range of hip rotation was more similar to the control condition when wearing thigh holster rather than the belt mounted hip holster (p<0.017). Moments and powers for both left and right ankles were significantly greater for both of the load carriage conditions compared to the control condition (p<0.017). InterpretationThis study confirms that occupational loads carried by police have a significant effect on gait kinematics and kinetics. Although small differences were observed between the two load carriage conditions investigated in this study, results do not overwhelmingly support selection of one design over the other.