Airbag Vests in Equestrian Sports: Is Use Associated with Harm?

Airbag vests (AV) are increasingly popular in equestrian sports. The efficacy of AV in protecting against serious injury has not been adequately analyzed, nor have product testing standards been established. This study provides an overview of current research to understand AV efficacy and future areas of improvement. A systematic review applying the PRISMA framework, NIH Study Quality Assessment, and CEBM Level of Evidence was conducted. Employing variations of "equestrian sport," "powered two-wheeled vehicle," "thoracic injury," "chest deflection," "airbag vest," and "safety vest," 18 articles were identified for data collection from three recognized research databases and citation searching. In laboratory settings, the ability of AV to protect against thoracic injuries was variable based on concurrent foam-based safety vest (SV) usage, impact speed, and impact mechanism. Studies that examined equestrian falls with AV found an association with increased injury rates and risk. SVs were shown to provide inconclusive efficacy in protecting against injuries in experimental and cohort studies. Protective capabilities depend on material, temperature, and impact mechanism. Further limiting use, equestrians reported not wearing, or incorrectly wearing SV due to unknown benefits, low comfort, and ill fit. In equestrian sports, based on published literature to date, AV have not been associated with a reduction in injury. AV appear to be associated with an increase in the risk of serious or fatal injuries in certain settings. However, research in this area is limited and future, large-scale studies should be conducted to further evaluate the efficacy of the air vests.

Effectiveness of Body Armor Against Shock Waves: Preventing Blast Injury in a Confined Space.

Introduction Blast injuries in modern society often occur owing to terrorist attacks in confined spaces, particularly in urban settings, indoors, and in vehicles, leading to significant damage. Therefore, it is important to focus on blast injuries in confined spaces rather than in conventional open-field experiments. Materials and methods We used an air-driven shock wave generator (blast tube) established indoors in 2017 and conducted basic research to potentially save the lives of patients with blast injuries. Under general anesthesia, pigs were divided into with body armor (BA) and without BA groups. The pigs were fixed in the measurement chamber with their dorsal chest directly exposed to the shock wave. The driving pressure was set at 3.0 MPa to achieve a mortality rate of approximately 50%. A generated shock wave was directly applied to the pigs. Comparisons were made between the groups with respect to cardiac arrest and survival, as well as apnea, bradycardia, and hypotension, which are the triad of blast lung. Autopsies were performed to confirm the extent of the organ damage. Statistical analysis was performed using Fisher's exact test, and statistical significance was set at p<0.05. The animal experimentation was conducted according to the protocol reviewed and approved by the Animal Ethics Committee of the National Defense Medical College Hospital (approval number 19041). Results Eight pigs were assigned to the BA group and seven pigs to the non-BA group. In the non-BA group, apnea was observed in four of seven cases, three of which resulted in death. None of the eight pigs in the BA group had respiratory arrest; notably, all survived. Hypotension was observed in some pigs in each group; however, there were no cases of bradycardia in either group. Statistical analysis showed that wearing BA significantly reduced the occurrence of respiratory and cardiac arrest (p=0.026) but not survival (p=0.077). No significant differences were found in other vital signs. Conclusions Wearing BA with adequate neck and chest protection reduced mortality and it was effective to reduce cardiac and respiratory arrest against shock wave exposure. Mortality from shock wave injury appears to be associated with respiratory arrest, and the avoidance of respiratory arrest may lead to survival.

A cluster-based law enforcement body armor sizing system: Concept, procedure, and design practice.

Given the evolution of human body dimensions, the increasing diversity within the law enforcement workforce, the growing risks of assault faced by law enforcement officers (LEOs), and the absence of a national standard for body armor sizing, there is a critical need to explore LEO body size classification. This exploration will facilitate the development of an armor sizing structure that adequately accommodates the current LEO population. This study aimed to address this need by developing a LEO body armor sizing scheme and creating a sizing chart/app. Additionally, a plan was devised for a series of 'sizing vests' that would enhance LEO armor accommodation and facilitate fit assessment. Torso anthropometric data pertaining to body armor sizing were collected from 756 male and 218 female LEOs across different regions of the United States. Based on the collected data, a nine-size system for male LEOs and an eight-size scheme for female LEOs were suggested. Furthermore, a sizing chart/app was proposed to enable LEOs to swiftly identify an armor size that is most likely to fit an individual, considering a few anthropometric characteristics known to LEOs. To supplement the sizing chart/app, a series of 'sizing vests' were recommended. These vests would provide LEOs with a physical means to assess and determine the best-fitting armor size, offering an alternative to relying solely on the sizing chart/app. We recommend that armor manufacturers adopt these new sizing systems and create prototypes of armor that can be evaluated within this sizing structure. This evaluation process will facilitate improved fit and enhanced protection for LEOs.

Low-Temperature-Tolerant Strain-Sensing Flexible Composite for Soft Body Armor.

Developing soft body armor with sensing characteristics in various application scenarios is a challenge but important for creating a peaceful world and personal safety, whereas existing materials suffer from indefinite protective effects and stimulus response at subzero temperatures in the long term. Herein, an anti-freezing and flexible puncture-resistance composite with strain-sensing ability is developed by compounding a NaCl-soaked poly(vinyl alcohol) (PVA)/sodium alginate (SA)/glycerol (Gly) hydrogel (PSGN hydrogel) with Kevlar fabric. After freezing-thawing treatment once and NaCl immersion for 10 h, the Kevlar/PSGN-10 composite has excellent puncture-resistance properties and linear, rapid response, wide band, and stable strain-sensing behaviors at 25 and -30 °C. The composite's maximum puncturing force and energy dissipation at -30 °C are 53.92 N and 370 mJ, respectively, increased by 285 and 302% compared with neat Kevlar fabric. The flexibility reduction and the mass addition of the Kevlar/PSGN-10 composite are merely 19 and 40%, respectively, showing superior wearable comfortability and protection efficiency. The composites also reveal remarkable strain-sensing abilities at -30 °C (linear strain sensitivity with GF = 0.27 and R2 = 0.981, a wide working frequency range of 0.16-1.3 Hz, and sensing stability for 1500 cycles). Moreover, the composite could respond to multipart body motion directly, including fingers, elbows, wrists, and knees. Consequently, the Kevlar/PSGN composite developed in this paper is promising for intelligent soft body armor at various temperatures.

Anti-Ballistic Performance of PPTA/UHMWPE Laminates.

Poly(p-phenylene terephthalamide) (PPTA) and ultra-high-molecular-weight polyethylene (UHMWPE) are high-performance polymer materials largely used for body armor applications. Although composite structures from a combination of PPTA and UHMWPE have been created and described in the literature, the manufacture of layered composites from PPTA fabrics and UHMWPE films with UHMWPE film as an adhesive layer has not been reported. Such a new design can provide the obvious advantage of simple manufacturing technology. In this study, for the first time, we prepared PPTA fabrics/UHMWPE films laminate panels using plasma treatment and hot-pressing and examined their ballistic performance. Ballistic testing results indicated that samples with moderate interlayer adhesion between PPTA and UHMWPE layers exhibited enhanced performance. A further increase in interlayer adhesion showed a reverse effect. This finding implies that optimization of interface adhesion is essential to achieve maximum impact energy absorption through the delamination process. In addition, it was found that the stacking sequence of the PPTA and UHMWPE layers affected ballistic performance. Samples with PPTA as the outermost layer performed better than those with UHMWPE as the outermost layer. Furthermore, microscopy of the tested laminate samples showed that PPTA fibers exhibited shear cutting failure on the entrance side and tensile failure on the exit side of the panel. UHMWPE films exhibited brittle failure and thermal damage at high compression strain rate on the entrance side and tensile fracture on the exit side. For the first time, findings from this study reported in-field bullet testing results of PPTA/UHMWPE composite panels, which can provide important insights for designing, fabricating, and failure analysis of such composite structures for body armors.

Association between physiological and perceptual heat strain while wearing stab-resistant body armor.

In this study, we explored the association between physiological and perceptual heat strain while wearing stab-resistant body armor (SRBA). Human trials were performed on ten participants in warm and hot environments. Physiological responses (core temperature, skin temperature, and heart rate), and perceptual responses (thermal sensation vote, thermal comfort vote, restriction of perceived exertion (RPE), wetness of skin, and wetness of clothing) were recorded throughout the trials, and subsequently, the physiological strain index (PSI), and perceptual strain index (PeSI) were calculated. The results indicated that the PeSI showed a significant moderate association with the PSI, and was capable of predicting PSI for low (PSI = 3) and high (PSI = 7) levels of physiological strain with the areas under the curves of 0.80 and 0.64, respectively. Moreover, Bland-Altman analysis indicated that the majority of the PSI ranged within the 95% confidence interval, and the mean difference between PSI and PeSI was 0.14 ± 2.02 with the lower 95% limit and upper 95% limit being -3.82 to 4.10, respectively. Therefore, the subjective responses could be used as an indicator for predicting physiological strain while wearing SRBA. This study could provide fundamental knowledge for the usage of SRBA, and the development of physiological heat strain assessment.

A new biomechanical FE model for blunt thoracic impact.

In the field of biomechanics, numerical procedures can be used to understand complex phenomena that cannot be analyzed with experimental setups. The use of experimental data from human cadavers can present ethical issues that can be avoided by utilizing biofidelic models. Biofidelic models have been shown to have far-reaching benefits, particularly in evaluating the effectiveness of protective devices such as body armors. For instance, numerical twins coupled with a biomechanical model can be used to assess the efficacy of protective devices against intense external forces. Similarly, the use of human body surrogates in experimental studies has allowed for biomechanical studies, as demonstrated by the development of crash test dummies that are commonly used in automotive testing. This study proposes using numerical procedures and simplifying the structure of an existing biofidelic FE model of the human thorax as a preliminary step in building a physical surrogate. A reverse engineering method was used to ensure the use of manufacturable materials, which resulted in a FE model called SurHUByx FEM (Surrogate HUByx Finite Element Model, with HUByx being the original thorax FE model developed previously). This new simplified model was validated against existing experimental data on cadavers in the context of ballistic impact. SurHUByx FEM, with its new material properties of manufacturable materials, demonstrated consistent behavior with the corresponding biomechanical corridors derived from these experiments. The validation process of this new simplified FE model yielded satisfactory results and is the first step towards the development of its physical twin using manufacturable materials.

Effect of Aging on Unidirectional Composite Laminate Polyethylene for Body Armor.

The construction of ballistic-resistant body armor is experiencing an increasing use of flexible unidirectional (UD) composite laminates that comprise multiple layers. Each UD layer contains hexagonally packed high-performance fibers with a very low modulus matrix (sometimes referred to as binder resins). Laminates are then made from orthogonal stacks of these layers, and these laminate-based armor packages offer significant performance advantages over standard woven materials. When designing any armor system, the long-term reliability of the armor materials is critical, particularly with regard to stability with exposure to temperature and humidity, as these are known causes of degradation in commonly used body armor materials. To better inform future armor designers, this work investigates the tensile behavior of an ultra-high molar mass polyethylene (UHMMPE) flexible UD laminate that was aged for at least 350 d at two accelerated conditions: 70 °C at 76% relative humidity (RH) and 70 °C in a desiccator. Tensile tests were performed at two different loading rates. The mechanical properties of the material after ageing demonstrated less than 10% degradation in tensile strength, indicating high reliability for armor made from this material.

Stab-Resistant Polymers-Recent Developments in Materials and Structures.

Stab-resistant garments have been used for centuries, utilizing metals, paper, or polymeric structures, often inspired by natural structures such as scales. Nowadays, stab-resistant vests or vest inserts are used by police and security personnel, but also by bus drivers, ambulance officers, and other people who are empirically often attacked on duty. Since stab protection garments are often heavy and thus uncomfortable and not well accepted, whether in the form of chain-mail or metal inserts in protective vests, researchers are striving to find lightweight, drapable alternatives, often based on polymeric materials. These research attempts have recently focused on textile fabrics, mostly with impregnation by shear-thickening fluids (STFs) or ceramic coatings, as well as on lightweight composites. The first studies on 3D printed polymeric objects with tailored shapes, as well as theoretical investigations of the stab-protective effect of different materials, have been published throughout the last years. Here, we discuss different measurement methods, including dynamic and quasistatic methods, and correlations of stab-resistance with other physical properties, before we give an overview of recent developments of stab-resistant polymers, using different materials/material combinations and structures.

Impact-Protective Bicontinuous Hydrogel/Ultrahigh-Molecular Weight Polyethylene Fabric Composite with Multiscale Energy Dissipation Structures for Soft Body Armor.

Soft body armor greatly improves the comfort and security of the wearers. Although laminates based on high-performance fabrics have been adopted, it remains an enormous challenge to develop fabric laminates having flexibility, low bulge deformation, and ballistic protection capability simultaneously. Herein, we report a bullet-proof bicontinuous hydrogel (BH)/ultrahigh-molecular weight polyethylene fabric (UPF) composite. The presence of the BH significantly improves the impact resistance performance of the UPF, without compromising its flexibility. In specific, the multiscale energy dissipation structures composed of hydrogen bond associations in the chain scale, bicontinuous phase structures in the nanoscale, and fibers in the microscale are broken to dissipate energy. As a result, the impact energy of the bullet is greatly absorbed and the bulge height of the composites is significantly reduced in contrast to the neat UPF laminates. This study indicates that the flexible BH-UPF composites with multiscale energy dissipation structures have a promising application in soft body armor.

Stab-Resistant Performance of the Well-Engineered Soft Body Armor Materials Using Shear Thickening Fluid.

Stab-resistant body armor can effectively prevent sharp instruments from attacking the protected parts and reduce the threat to human bodies. Shear thickening fluid (STF) is a kind of smart material with variable viscosity and its viscosity can change significantly with external stimuli. The soft and adaptive characteristics of STF provide a new idea for improving the performance of stab-proof materials. In this work, three kinds of soft anti-stabbing materials were designed and prepared with aramid, poly-p-phenylene benzodioxazole (PBO), and carbon fiber fabrics impregnated with STF. Quasi-static puncture tests and dynamic impact tests were conducted to compare the performance of different anti-stabbing structures. The results showed that the peak piercing force of the STF-treated fabrics in the puncture testing was greatly increased than that of neat samples. Against the D2 knife, the maximum impact load of STF/PBO fiber fabric was increased from 55.8 N to 72.9 N, increasing by 30.6%. Against the D3 spike, the maximum impact load of STF/aramid fabric was increased from 128.9 N to 254.7 N, increasing by 197.6%. The mechanical properties of fibers were important factors for the resistance to knives, and the fabric structure was the key point to bear the spike. Optical photographs of fabric fractures and scanning electron microscope analysis indicated that the STF effectively limited the slip of the fiber bundle when the tool penetrated the fabric, which played a positive role in maintaining the tightness and integrity of the fabric structure.

Multifunctional Polyurethane Composite Foam with Outstanding Anti-impact Capacity for Soft Body Armors.

Herein, a multifunctional polyurethane (PU) composite foam with a hierarchical structure is fabricated by dip-coating a carbon nanotube/shear-thickening gel (CNT/STG) and spray-coating nano-SiO2/STG on PU foam. The prepared nano-SiO2/CNT/STG@PU (SCS@PU) composite foam is lightweight, highly compressive, electrically conductive, superhydrophobic, and impact-energy absorptive. As a result, it possesses an excellent sensing ability to compression with a stable response up to 80% strain, an outstanding linearity of R2 > 0.99, and a wide response frequency of 0.01 to 1 Hz; it can also be used for effectively detecting impact force and sensing various human motions. Moreover, the superhydrophobicity with a water contact angle up to 154° of SCS@PU composite foam endows it with an excellent resistance to hazardous liquids (strong acid and alkali) to ensure its service reliability under harsh circumstances. In particular, the SCS@PU exhibits an outstanding anti-impact capability with an impact force attenuation rate of SCS@PU as high as 81%. Finally, its applications as soft body armors are demonstrated in protecting a wearer wearing a helmet with the SCS@PU as liner and using the SCS@PU as a smart kneecap against impact. On consideration of its excellent strain-sensing ability, superhydrophobicity, and outstanding anti-impact capability, the multifunctional SCS@PU composite foam developed is promising for personal safety protection.

Effects of a liquid cooling vest on physiological and perceptual responses while wearing stab-resistant body armor in a hot environment.

This study determines the effects of a liquid cooling vest (LCV) on physiological and perceptual responses while wearing stab-resistant body armor (SRBA). Ten healthy male volunteers wearing SRBA performed human trials with the LCV and without (control) in a hot environment (30 °C and 40% relative humidity). Physiological parameters and perceptual responses were recorded during the tests. The results indicated that the difference in the mean skin temperature and scapula skin temperature between the two conditions was up to 1.2 and 2.5 °C, respectively. The LCV did not significantly decrease the core temperature, heart rate, sweat loss, oxygen consumption, rating of perceived exertion and restriction of movement. However, a significant difference was observed between conditions in terms of evaporation efficiency and thermal sensation. Therefore, the LCV attenuated an increase in thermal sensation but did not mitigate physiological strain. This work can provide fundamental knowledge for high-performance personal cooling system development.

Sternal Gap Syndrome Caused by Improperly Fitted Body Armor: A Preventable Military Injury.

Isolated atrophy of the pectoralis major muscle (PMM) secondary to traumatic lesion of the medial pectoral nerve is a known entity in the field of neuromuscular electrodiagnostics. Recent literature has begun describing a Pectoral Gap Phenomenon in which this atrophy occurs bilaterally as an overuse injury, leading to a marked concavity in the central chest wall musculature. While there is limited information in science journals on this topic, social media posts on weight lifting discuss the topic frequently. We report a case in which a soldier's body armor crushed the lateral medial and pectoral nerves against the anterior chest wall causing permanent upper body weakness. To optimize military medical readiness, awareness of this disorder and the pathophysiology causing it should spread so as to mitigate this potential for significant disability.

The effect of physical training modality on exercise performance with police-related personal protective equipment.

PURPOSE: To investigate the influence of aerobic capacity, muscle strength, and body composition on performance and metabolic demands of men wearing personal protective equipment (PPE). METHODS: 45 men were assigned to one of four groups which significantly differed in upright pull isometric strength (MVC ≤ 1325 N or ≥ 1531 N) and maximum oxygen uptake (VO2max ≤ 51.9 mL min-1·kg-1 or ≥ 56.0 mL min-1·kg-1): endurance-trained (low MVC, high VO2max), strength-trained (high MVC, low VO2max), endurance- and strength-trained (high MVC, high VO2max), and untrained (low MVC, low VO2max). Each participant underwent two test series consisting of a repeated 10 m dummy drag and a graded exercise test wearing either sportswear or PPE of a German riot police unit weighing 20.9 kg (statistics: two-way repeated measures ANOVA, stepwise multiple linear regressions). RESULTS: With PPE, dummy drag and running performance were impaired by 14 ± 9% and 58 ± 7%. Groups with high MVC dragged the dummy significantly faster than groups with low MVC (17.5 ± 1.8 s/17.6 ± 1.4 s vs. 23.4 ± 5.6 s/22.3 ± 3.5 s). Running distance was significantly higher in groups with high VO2max (4.5 ± 0.8 km/4.4 ± 0.7 km vs. 3.1 ± 0.5 km/2.8 ± 0.5 km). Body composition variables partially correlated with performance (R ranging from -0.70 to 0.41), but were not significant predictors of the regression models in PPE. CONCLUSIONS: Individuals who showed a certain degree of aerobic endurance, as well as muscle strength, performed consistently well during the test series. Therefore, none of these variables should be trained in isolation but optimized in combination to be capable in a variety of operational tasks.

Structural and mechanical properties of fish scales for the bio-inspired design of flexible body armors: A review.

Natural protection offered to living beings is the result of millions of years of biological revolution. The protections provided in fishes, armadillos, and turtles by unique hierarchal designs help them to survive in surrounding environments. Natural armors offer protections with outstanding mechanical properties, such as high penetration resistance and toughness to weight ratio. The mechanical properties are not the only key features that make scales unique; they are also highly flexible and breathable. In this study, we aim to review the structural and mechanical characteristics of the scales from ray-finned or teleost fishes, which can be used for new bio-inspired armor designs. It is also essential to consider the hierarchical structure of extinct and existing natural armors. The basic characteristics, as mentioned above, are the foundation for developing high-performance, well-structured flexible natural armors. Furthermore, the present review justifies the importance of interaction between toughness, hardness, and deformability in well-engineered bio-inspired body armor. At last, some suggestions are proposed for the design and fabrication of new bio-inspired flexible body armors.

Assessment of Thorax Finite Element Model Response for Behind Armor Blunt Trauma Impact Loading Using an Epidemiological Database.

Nonperforating ballistic impacts on thoracic armor can cause blunt injuries, known as behind-armor blunt trauma (BABT). To evaluate the potential for this injury, the back face deformation (BFD) imprinted into a clay backing is measured; however, the link between BFD and potential for injury is uncertain. Computational human body models (HBMs) have the potential to provide an improved understanding of BABT injury risk to inform armor design but require assessment with relevant loading scenarios. In this study, a methodology was developed to apply BABT loading to a computational thorax model, enhanced with refined finite element mesh and high-deformation rate mechanical properties. The model was assessed using an epidemiological BABT survivor database. BABT impact boundary conditions for 10 cases from the database were recreated using experimentally measured deformation for specific armor/projectile combinations, and applied to the thorax model using a novel prescribed displacement methodology. The computational thorax model demonstrated numerical stability under BABT impact conditions. The predicted number of rib fractures, the magnitude of pulmonary contusion, and injury rank, increased with armor BFD, back face velocity, and input energy to the thorax. In three of the 10 cases, the model overpredicted the number of rib fractures, attributed to impact location positional sensitivity and limited details from the database. The integration of an HBM with the BABT loading method predicted rib fractures and injury ranks that were in good agreement with available medical records, providing a potential tool for future armor evaluation and injury assessment.

The Impact of External Loads Carried by Police Officers on Vertical Jump Performance.

The purpose of this study was to examine the impact that external loads have on vertical jump height and peak anaerobic power output (PAPw) of police officers during a vertical jump (VJ) test. Retrospective data of 47 (mean age 38.79 ± 7.97 years) police officers from a US Law Enforcement Agency (LEA) were used for analysis. VJ heights and body mass were used in the Sayers Peak Power Equation to calculate PAPw. Power-to-weight (P:W) ratios were then calculated by dividing PAPw by the officer's body mass. VJ height significantly (p < .001) decreased with load (unloaded = 49.49 ± 8.46 cm: loaded = 43.62 ± 7.68 cm). A Pearson's correlation showed a significant (p < .01) low-moderate (r = .387) relationship between absolute load (9.57 ± .94 kg) and change in PAPw, and a significant (p < .01) strong (r = .794) correlation between relative load and changes in P:W. This study supports previous research that suggests that occupational load carriage has a negative impact on VJ performance in police officers and may influence job performance, and that training programs may mitigate these negative effects.

Tensile Testing of Aged Flexible Unidirectional Composite Laminates for Body Armor.

Flexible Unidirectional (UD) composite laminates are commonly being used for ballistic-resistant body armor. These laminates comprise UD layers, each constructed by laminating thin layers of high-performance fibers held in place using very low modulus binder resins, with the fibers in each layer oriented parallel to each other. As these materials are used in body armor, it is important to investigate their long-term reliability, particularly with regards to exposure to temperature and humidity as these are known causes of degradation in other commonly used body armor materials. This work investigates the tensile behavior of a poly(p-phenylene terephthalamide), or PPTA flexible UD laminate aged for up to 150 d at accelerated conditions of 70 °C and 76 % relative humidity (RH). Tests were performed at three different crosshead displacement rates and three different gauge lengths. The effect of ageing on the mechanical properties of the material resulted in less than 10 % degradation in tensile strength, with a more significant reduction in longer specimens when tested at slower rates.

[Mechanism of formation and morphological features of a gunshot injury to the chest and abdomen arising from the use of body armor]. / Mekhanizm obrazovaniya i morfologicheskie osobennosti ognestrel'noi travmy grudi i zhivota, voznikayushchei pri ispol'zovanii bronezhileta.

The features of a gunshot injury arising in the presence of body armor on the injured person are considered. The purpose of the work is to reveal the mechanisms of damage formation during non-penetration of an armored composition, during its penetration, as well as during external or internal rebound. The characteristic of damages arising with this is given. It was shown that injuries due to non-penetration of body armor are characterized mainly by local closed injuries, not only of integumentary soft tissues, but also of internal organs in the projection of impact of a wounding projectile. With through penetration of body armor, the severity and volume of gunshot damage increase due to the introduction of fragments of bullets, fragments of armored panels and pieces of equipment into the wound channel. Rebounding of elements of dismantled bullets from the outer or inner surface of the body armor can cause severe gunshot damage to both the wearer of body armor and other persons. Knowledge of the mechanisms of formation and morphological features of injuries that occur when using body armor are prerequisites for a full forensic medical assessment of the investigated incident.