TY - JOUR
AU - Doubrava,, Matthew
AB - Abstract Introduction Military training involves preparing individuals for combat, yet applying the stressors of combat while maintaining a safe training environment is exceedingly difficult. One method to induce significant anxiety while still maintaining reasonable safety has been to utilize simulated ammunition. These rounds enable force-on-force training with reasonable stress and firing accuracy while also readily allowing participants to realize they have been shot. As such, these rounds have significant value when performing force-on-force training. However, although in widespread use, there has not been a documented medical effort assessing the subjective pain experienced by individuals after being struck by one of these rounds, nor a visual record tracking recovery. The current investigation presents pilot data collected from an existing training course to provide an assessment of superficial ballistic trauma inflicted by simulated ammunition. Materials and Methods Participants completed one-on-one duels as part of their intended course curriculum. These individuals used 9 mm pistols firing marking cartridges while wearing only prescribed protection equipment, leaving the chest, arms, and hands minimally covered by typical clothing. Participants engaged in the duels as overseen by the instructors and without guidance or interference by the experiment team. After an individual completed these drills, researchers then asked questions about subjective pain experience while also documenting the recovery via photographs. Results Results indicated that simulated ammunition only inflicted a mild amount of subjective pain, which reduced to zero even upon palpation after only a few days. Subjective pain for the chest was rated slightly higher than any other region. The visual record documented that most contusions were reduced to minor bruising, largely dissipating as quickly as the pain. Conclusions Participants were able to safely conduct force-on-force training with simulated ammunition by following the manufacturer recommended safety standards. Participants did rate a statistically significant level of subjective pain, although this mild pain serves as a necessary factor to create the stressful environment of simulating combat conditions. It is possible that the subjective pain was rated higher for the chest due to the increased number of total rounds striking the chest, or the more direct impact of the rounds upon this tissue. The differences in subjective pain and recovery between impact regions of the body are likely due to the specific force-on-force drill conducted as a part of this training. Additional research will be necessary to support or dispute this latter speculation. Military operations are among the highest stress-inducing activities in which any human can engage. However, there is no way to accurately replicate combat stressors in a safe environment or training simulation. This limitation has driven trainers to seek alternate, yet reasonably safe means of replicating the anxiety associated with combat. One currently available method involves using simulated ammunition that can be fired without inflicting a lethal round, sometimes from service-issued weapons. The intent is to provide operators with ammunition that will enable force-on-force training, let individuals know when they have been shot, create anxiety during the process, and remain reasonably accurate when fired. These non-lethal rounds have been used effectively in recent force-on-force training to induce significant levels of stress.1,2 Despite the widespread nature of simulated ammunition use, there is extremely limited public data about safety and medical issues associated with using these rounds. Instead, safety is determined almost entirely by physics associated with the ballistics and not any associated medical standard. Unfortunately, there are no industry standards, bench studies, animal work, cadaver work, or previous human testing with research-approved data collection or quantifiable statistics. Safety standards are set by the individual manufacturers, who do not always disclose how they arrived at said safety standards and note only that laboratory testing was conducted. Safety standards can also differ by product, and it is ultimately left to the individual military and law enforcement units to enforce safety standards as they see fit. In short, there are no steadfast safety standards or requirements in the use of simulated ammunition. If these rounds are among the most realistic means of simulating combat during training, and these rounds are known to increase stress by inflicting real wounds, then it is essential to understand what pain is experienced and what the expected wounds will be. Given the importance of simulated ammunition to training, especially as it pertains to force-on-force work, we conducted a pilot medical evaluation as an observation of convenience during an existing training course. Our assessments had three primary goals: (1) identify subjective pain experienced by individuals while using simulated ammunition during force-on-force training, (2) document how long this superficial ballistic trauma continued to cause pain following the initial assessment, and (3) determine whether the recommended safety standards were indeed sufficient if non-lethal training ammunition was used in accordance with manufacturer recommendations. The current impact assessments focused upon the torso as the vast majority of rounds struck the upper body. No specific instruction was given to aim for specific body areas for the purposes of medical assessments, and so this evaluation is one of convenience and dependent entirely upon the specific drill performed. For this reason, the analyses are not corrected for multiple comparisons because all analyses are themselves dependent on factors beyond experimental design or control. METHODS Participants, Course Description, and Simulated Ammunition Participants were 17 U.S. Marines. They participated in a course designed to enhance close quarters marksmanship, which included force-on-force drills. The particular drill evaluated here involved one-on-one dueling scenarios in a 16’ × 9.5’ space. Instructors would call out the target area or other criteria for cessation. Participants were free to move about this space and actively encouraged to move rather than remain still. Minimal protective equipment was worn that conformed to recommended safe guidelines,3 including face, head, and throat protection. Participants were given 9 mm simulations pistols with variable amounts of 9 mm FX Marking Cartridges from Simunition. Hands-on combat was not permitted. The training course administered an existing training regimen scheduled regardless of this investigation. As such, this project was approved by the Naval Medical Research Unit Dayton Institutional Review Board with the understanding that the researchers were in no way asking participants to be shot for this examination. Force-on-force exercises proceeded regardless of medical assessment, and as such, researchers would only investigate superficial trauma as an opportunity of convenience and for greater medical knowledge rather than a carefully orchestrated evaluation requiring data from specific impact locations. Assessment and Procedure Subjective pain was the primary outcome measure. Experimenters evaluated subjective pain during initial assessment and for several days of follow-up assessments until reported pain measurements reached statistical non-significance. Marines were not screened for pain prior to the initial assessment; however, the superficial ballistic trauma characterized the first and only wounds associated with this marksmanship training throughout the assessment period. As the only exercise of its type during the assessment period, the procedure helps assure the subjective pain associated with simulated ammunition usage remains the primary if not sole source of physical pain and discomfort. Participants were asked about any subjective pain with or without visible wounds for body regions that received significant hits during training, and if any region was reported as painful during the initial assessment, these areas were tracked for subjective pain experienced by the individual. Because individual shots could not be predicted in advance and many shots overlapped, 6 areas were broadly categorized as likely areas where participants might be shot: chest, abdomen, upper arm, forearm, hands, or fingers. If there was visible ecchymosis or reported pain, an initial assessment was made. During initial assessment, individuals were assessed for overall subjective pain experienced in this region by responding based upon the provided scale (see Table I). This range was chosen to approximate a well-validated range of the Wong-Baker FACES pain rating scale.4 However, only the Likert-type scale was used and not the faces to avoid potentially biasing military participants in their ratings. TABLE I. Scale Used to Report Pain at Simulated Ammunition Impact Assessment as Presented to Subjects 0 1 2 3 4 5 6 7 8 9 10 0 – No pain at all 2 – Mild, annoying pain 4 – Uncomfortable or troublesome pain 6 – Distressing pain 8 – Intense pain 10 – Worst pain imaginable 0 1 2 3 4 5 6 7 8 9 10 0 – No pain at all 2 – Mild, annoying pain 4 – Uncomfortable or troublesome pain 6 – Distressing pain 8 – Intense pain 10 – Worst pain imaginable TABLE I. Scale Used to Report Pain at Simulated Ammunition Impact Assessment as Presented to Subjects 0 1 2 3 4 5 6 7 8 9 10 0 – No pain at all 2 – Mild, annoying pain 4 – Uncomfortable or troublesome pain 6 – Distressing pain 8 – Intense pain 10 – Worst pain imaginable 0 1 2 3 4 5 6 7 8 9 10 0 – No pain at all 2 – Mild, annoying pain 4 – Uncomfortable or troublesome pain 6 – Distressing pain 8 – Intense pain 10 – Worst pain imaginable Secondary outcome measures involved assessments of any visible ecchymosis to track individual recovery. These assessments helped track areas associated with subjective pain, although the consideration of visible wounds remained secondary for several reasons: (1) not every individual received a visible wound or cluster of wounds suitable for analyses, (2) shots could overlap, making it difficult to isolate individual wounds, and (3) field training conditions made it difficult to create a complete and reliable visual record for tracking wound recovery. As such a visual record of ecchymosis recovery is provided as a secondary outcome measure and primarily for illustrative purposes. Once participants stopped reporting any associated pain with superficial ballistic trauma, a final assessment was made and questions concluded. No other force-on-force activities occurred during this evaluation period, which allowed for an isolated determination of these wounds and made them easier to track. Individual area assessments are broken down based upon whether subjective pain was significantly different than zero, thereby indicating painful experience, and whether the pain was felt at rest, during movement, or on palpation. An assessment of pain more different than zero was calculated as a one sample t test.5 Any other comparisons were conducted as paired samples t tests. Lesser reported pain values for several other regions could be due to the small sample sizes. However, other factors could also be involved, such as reduced pain in the forearm because it is unlikely to take a direct hit if two shooters have their arms fully extended. As such, many shots could have glanced off the skin rather than making direct contact. Of these various regions, analyses of impacts only to the torso and hands are considered reliable due to their relatively larger sample sizes. RESULTS Although the precise rate of impact trauma per fired round could not be calculated, estimates were based upon several known variables. For example, a total of 828 9 mm simulated ammunition rounds were fired during the dueling exercise, after which the initial medical assessments were determined and ammunition impacts were tracked for several following days. However, it should be noted that the following numbers represent only the reported drills here and could vary greatly based upon individual shooter proficiency and whether the rounds struck protective equipment. Protective equipment is particularly important as rounds should not leave any mark or inflict pain if striking protective gear, and there is no available estimate for rounds striking the gear. For the current training initiative, the 4 marksmanship instructors each provided an estimate about the percentage of rounds fired that struck a target. The average of these 4 estimations was 80% (SD = 6.77%), which indicates that approximately 662 of the rounds fired struck another person. Of the 662 probable rounds that landed, experimenters made 57 assessments of areas impacted with at least one simulated ammunition impact: chest (N = 16), abdomen (N = 7), upper arm (N = 8), forearm (N = 8), hand (N = 13), and fingers (N = 5). These assessments represent body regions and not individual wounds. As such, these data represent of subjective pain assessments tracked for 17 participants and not actual number of rounds that left a visible ecchymosis, which experimenters were unable to track without interfering with the training course. See Table II for summary of changes in significant subjective pain experienced. TABLE II. Significant Subjective Pain as Reported Based Upon Region of Impact and Time Since Impact Time Since Impact Impact Area Immediately After Day 1 Day 2 Day 3 Day 4 Chest (N = 16) * - - - - Rest * * - - - Movement * * * - - Palpation Abs (N = 7) Rest - - - - - Movement * - - - - Palpation * * - - - Upper Arm N = 8) Rest - - - - - Movement - - - - - Palpation - - - - - Forearm N = 8) Rest * - - - - Movement * - - - - Palpation * - - - - Hand N = 13) Rest * - - - - Movement * * - - - Palpation * * * - - Fingers (N = 5) Rest * - - - - Movement * - - - - Palpaion * * - - - Time Since Impact Impact Area Immediately After Day 1 Day 2 Day 3 Day 4 Chest (N = 16) * - - - - Rest * * - - - Movement * * * - - Palpation Abs (N = 7) Rest - - - - - Movement * - - - - Palpation * * - - - Upper Arm N = 8) Rest - - - - - Movement - - - - - Palpation - - - - - Forearm N = 8) Rest * - - - - Movement * - - - - Palpation * - - - - Hand N = 13) Rest * - - - - Movement * * - - - Palpation * * * - - Fingers (N = 5) Rest * - - - - Movement * - - - - Palpaion * * - - - Significant pain is determined as the reported score being significantly different from zero in a one sample t-test. Asterisks indicate a significant reported level of subjective pain, and dashes indicate a level of reported pain not significantly different from zero. TABLE II. Significant Subjective Pain as Reported Based Upon Region of Impact and Time Since Impact Time Since Impact Impact Area Immediately After Day 1 Day 2 Day 3 Day 4 Chest (N = 16) * - - - - Rest * * - - - Movement * * * - - Palpation Abs (N = 7) Rest - - - - - Movement * - - - - Palpation * * - - - Upper Arm N = 8) Rest - - - - - Movement - - - - - Palpation - - - - - Forearm N = 8) Rest * - - - - Movement * - - - - Palpation * - - - - Hand N = 13) Rest * - - - - Movement * * - - - Palpation * * * - - Fingers (N = 5) Rest * - - - - Movement * - - - - Palpaion * * - - - Time Since Impact Impact Area Immediately After Day 1 Day 2 Day 3 Day 4 Chest (N = 16) * - - - - Rest * * - - - Movement * * * - - Palpation Abs (N = 7) Rest - - - - - Movement * - - - - Palpation * * - - - Upper Arm N = 8) Rest - - - - - Movement - - - - - Palpation - - - - - Forearm N = 8) Rest * - - - - Movement * - - - - Palpation * - - - - Hand N = 13) Rest * - - - - Movement * * - - - Palpation * * * - - Fingers (N = 5) Rest * - - - - Movement * - - - - Palpaion * * - - - Significant pain is determined as the reported score being significantly different from zero in a one sample t-test. Asterisks indicate a significant reported level of subjective pain, and dashes indicate a level of reported pain not significantly different from zero. Thorax. Sixteen students reported pain in the superficial anterior or lateral aspects of the chest. See Figure 1 for examples (and Supplementary Material for additional photographs and analyses, including Supplementary Figures S1–S6). Analyses regarding the thorax are most reliable due to the higher number of data points, which is likely a consequence of students being told to aim for the chest during some drills. Participants reported a significant experience of pain at first assessment (Mean = 1.54, SE = 0.36), t(15) = 4.33, p < 0.001, Cohen’s d = 1.08, on the first day after impact (Mean = 0.40, SE = 0.12), t(15) = 3.33, p < 0.01, Cohen’s d = 0.83, and on the second day after impact (Mean = 0.19, SE = 0.09), t(15) = 2.06, p = 0.03, Cohen’s d = 0.51. The subjective pain reported on the third day was non-significant (Mean=0.04, SE = 0.03), t(15) = 1.46, p = 0.08, Cohen’s d = 0.37, and no pain was reported by the fourth day after initial impact. Pain reduction for the first day after impact relative to the initial impact was a significant decline, t(15) = 3.71, p < 0.001, Cohen’s d = 1.08, as was the pain reduction from the first day after impact to the second day after impact, t(15) = 2.82, p = 0.01, Cohen’s d = 0.49. These results indicate some lingering discomfort following initial impact that persisted for several days, but none of the subjects reported any pain, whether at rest, during movement, or upon palpation, four days after the initial impact. FIGURE 1. View largeDownload slide Panel of photographs depicting superficial ballistic trauma to the anterior aspect of the thorax for 3 subjects and the pattern of recovery from during initial assessment to 4 days after impact. FIGURE 1. View largeDownload slide Panel of photographs depicting superficial ballistic trauma to the anterior aspect of the thorax for 3 subjects and the pattern of recovery from during initial assessment to 4 days after impact. Overall, there were no reported differences between subjective pain when describing pain at rest versus pain while moving during initial assessment, t(15) = 1.00, p = 0.33, no difference the day after initial impact, t(15) = 1.38, p = 0.19, no difference two days after impact, t(15) = 1.00, p = 0.33, and reported pain scores were identical on the third and fourth days after impact (Mean = 0.00). Initially, there were no significant differences between reported pain at rest versus on palpation during initial assessment, t(15) = 1.00, p = 0.33. However, there was significantly less pain experienced the day after initial impact at rest versus on palpation, t(15) = 4.04, p<0.001, Cohen’s d = 1.04, and this difference persisted two days after initial impact when less pain was experienced at rest versus on palpation, t(15) = 2.41, p = 0.03, Cohen’s d = 0.85. The difference became non-significant again three days after initial impact, t(15) = 1.46, p = 0.16, and there was no reported pain on the fourth day either at rest, during movement, or with palpation (Mean = 0.00). Taken together, these results indicate that superficial trauma was not enough to cause a difference in subjective pain between a resting state and during movement, although there was a significant increase in pain with palpation. Hand. Thirteen subjects reported pain in their hand region. Analyses regarding the hand region are the most reliable following the thoracic region due to the second highest number of assessments made; the hands, specifically the knuckles, were aligned with the sight profile and more likely to take a direct hit when participants aimed at the head. Participants reported a significant experience of pain during initial assessment (Mean = 0.95, SE = 0.42), t(12) = 2.25, p = 0.02, Cohen’s d = 0.62, on the first day after impact (Mean = 0.33, SE = 0.14), t(12) = 2.36, p=0.02, Cohen’s d = 0.65, and on the second day after impact (Mean = 0.15, SE = 0.08), t(12) = 1.90, p = 0.04, Cohen’s d = 0.53. The subjective pain reported on the third day was non-significant (Mean = 0.03, SE = 0.03), t(12) = 1.00, p=0.17, Cohen’s d = 0.28, and no pain was reported by the fourth day after initial impact. None of the reductions in pain were significantly different from day-to-day, p’s > 0.10. Overall, there were no reported differences between reported pain when describing pain at rest versus pain while moving during initial assessment, t(12) = 1.00, p = 0.34, no difference the day after initial impact, t(12) = 1.76, p = 0.10, no difference two days after impact, t(12) = 1.00, p = 0.34, and reported pain scores were identical on the third and fourth days after impact (Mean = 0.00). Initially, there were no significant differences between reported pain at rest versus on palpation during initial assessment, t(12) = 1.00, p = 0.34. However, there was significantly less pain experienced the day after initial impact at rest versus with palpation, t(12) = 2.52, p = 0.03, Cohen’s d = 0.79, and this difference persisted two days after initial impact when less pain was experienced at rest versus on palpation, t(12) = 2.13, p = 0.05, Cohen’s d = 0.84. The difference became non-significant again three days after initial impact, t(12) = 1.00, p = 0.34, and there was no reported pain on the fourth day either at rest, during movement, or with palpation (Mean = 0.00). Taken together, these results indicate that the superficial trauma was not enough to cause a difference in subjective pain between a resting state and during movement, although there was a significant increase in pain with palpation. DISCUSSION AND CONCLUSIONS The current investigation collected and documented the impact, subjective pain, and recovery period of superficial ballistic trauma by assessing wounds inflicted during an existing force-on-force training course. Through questionnaires and a photographic record, the evidence suggests that simulated ammunition caused a mild or annoying to uncomfortable level of pain among individuals who participated in the force-on-force drills. This superficial trauma included minor contusions, abrasions and lacerations that lasted for several days, although participants were not reporting any pain 4 days after initial impact. A critical concern is safety of participants in force-on-force drills when using simulated ammunition. The photographic evidence confirms the rounds have a terminal effect of non-lethal bruises, welts, and scrapes.6 Subjective pain corresponding with these injuries did not provoke a severe reaction and only became mildly worse with palpation relative to at rest or when moving. Impact trauma did appear visually worse for chest injuries, although this aspect may have more to do with the training paradigm than the rounds themselves. Dueling scenarios often had participants circling one another with arms extended and aiming for the head or chest region. The head remained covered with protective gear, which prevented any injury. Chest hits were then direct impacts, whereas upper arm or forearm impacts would be more likely to graze the region rather than strike cleanly. Injuries to the hands also appear less severe, possibly for the same reason, although this difference could also be attributable to the different tissue type with bone being less vulnerable to superficial ballistic trauma than soft tissue. Current manufacturer safety standards with a simulated ammunition product recommend a minimum stand-off training distance of 1 foot (30 cm) for 9 mm rounds for protected personnel using marking cartridges, where protected personnel are defined as personnel using approved mandatory head, throat, and groin protection.3 Given that the current safety standards are defined by the ballistics, we will consider the kinetics for a moment. A 9 mm simulated ammunition pistol kit is capable of firing with an average muzzle velocity of 110 m per second to 150 m per second (360–490 feet per second) with a muzzle energy of 3.0 to 5.6 joules, or 2.2 to 4.1 foot-pounds.6 Many factors impact the speed of a fired round, but to provide a baseline comparison to live ammunition, a 9 mm weapon can fire a live round at approximately 390 m per second.7 Previous evidence has demonstrated that the energy density required is between 23.99 J/cm2 to 52.74 J/cm2 to cause a penetrating wound with less than lethal kinetic energy munitions,8 or 9.8 N to 56.7 N when trying to push an improvised weapon through skin simulant.9 Taken together, this evidence means that a simulated round could be capable of creating a defect in the integumentary system if fired within 3–10 m of the target. The question thus becomes whether current manufacturer recommendations are indeed safe for training. Based on the evidence collected here, and presuming the manufacturers recommended safety standards are followed with regard to protective gear, the results appear to confirm the safety recommendations. These rounds do cause pain and injury, but the risk and severity of the injury must be balanced with the benefit of the skills gained by the training. The simulated ammunition round is safe for use only under a strictly supervised training program and only for actual training. This investigation was conducted as an opportunity of convenience and as such, the various assessments did not carefully control the tissue being impacted, the number of rounds impacting the tissue, or the precise distances under which the rounds struck soft tissue. Thus, the evidence collected was subject to a level of random chance, yet also accurately reflected realistic training expectations for the same reason. Still, perhaps the most important conclusion of the current evidence is the need for additional evidence. We have further validated the potential value of simulated ammunition by demonstrating its value in inflicting real pain during the exercises, yet this evidence is merely a small sample of the potential ammunition available and the associated wounds. There are numerous medical issues involved, and the type or brand of ammunition may matter as much as the specific drills. As such, we are not noting this work as a final determinant, but rather a call to arms in the need to have medical evaluations alongside human performance training evaluations of force-on-force drills. Put simply, this work is not an end state, but rather the beginning of what should be an extensive empirical medical and human performance evaluation program of simulated ammunition usage during force-on-force training. The value of realistic training cannot be underestimated for our personnel, and neither can the need to ensure the medical safety during such training. The current work does suggest that simulated ammunition impacts cause mild pain that can be resolved within a few days, and although additional questions exist, the current data provide empirical evidence that this ammunition can be used safely during force-on-force training. FUNDING This work was supported/funded by work unit number Z9PO. Office of Naval Research Code 30 (N0001418WX00247). ACKNOWLEDGMENTS The authors thank Alison Snyder for her comments on an earlier draft. HUMAN RESEARCH The study protocol was approved by the Naval Medical Research Unit Dayton Institutional Review Board in compliance with all applicable federal regulations governing the protection of human subjects. 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Science 2017 ; 8 ( 4 ): 355 – 362 . 6 As real as you can get with 9 mm and 38 cal . FX® Marking Cartridges. ( 2018 , July 24). Retrieved from: https://simunition.com/upload/documents/doc_96.pdf 7 Freire I. L , Apolinário J. A “GCC-based DoA estimation of overlapping muzzleblast and shockwave components of gunshot signals.” Circuits and Systems (LASCAS), 2011 IEEE Second Latin American Symposium on. IEEE, 2011 . 8 Bir C. A , Stewart S. J , Wilhelm M : Skin penetration assessment of less lethal kinetic energy munitions . J Forensic Sci 2005 ; 50 ( 6 ): JFS2004551 – 4 . Google Scholar Crossref Search ADS 9 Nolan G , Lawes S , Hainsworth S , Rutty G : A study considering the force required for broken glass bottles to penetrate a skin simulant . Int J Legal Med 2012 ; 126 ( 1 ): 19 – 25 . Google Scholar Crossref Search ADS PubMed Author notes The views expressed in this article reflect the results of research conducted by the author and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the United States Government. I am a military service member or federal/contracted employee of the United States government. This work was prepared as part of my official duties. Title 17 U.S.C. 105 provides that “copyright protection under this title is not available for any work of the United States Government.” Title 17 U.S.C. 101 defines a U.S. Government work as work prepared by a military service member or employee of the U.S. Government as part of that person’s official duties. © Association of Military Surgeons of the United States 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. 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TI - Superficial Ballistic Trauma and Subjective Pain Experienced during Force-on-Force Training and the Observed Recovery Pattern
JF - Military Medicine
DO - 10.1093/milmed/usz061
DA - 2019-04-05
UR - https://www.deepdyve.com/lp/oxford-university-press/superficial-ballistic-trauma-and-subjective-pain-experienced-during-ssxrqcOPBc
SP - 1
VL - Advance Article
IS - 
DP - DeepDyve
ER -