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The Australian Defence Force Parachute Training School instructs trainees to make initial ground contact using a flat foot whereas United States paratroopers are taught to contact the ground with the ball of the foot first. This study aimed to determine whether differences in foot pitch affected parachute landing technique. Kinematic, ground reaction force and electromyographic data were analyzed for 28 parachutists who performed parachute landings (vertical descent velocity = 3.4 m x s(-1)) from a monorail apparatus. Independent t-tests were used to determine significant (p < 0.05) differences between variables characterizing foot pitch. Subjects who landed flat-footed displayed less knee and ankle flexion, sustained higher peak ground reaction forces, and took less time to reach peak force than those who landed on the balls of their feet. Although forefoot landings lowered ground reaction forces compared to landing flat-footed, further research is required to confirm whether this is a safer parachute landing strategy. [ABSTRACT FROM AUTHOR]

To optimise soldier protection within body armour systems, knowledge of the boundaries of essential thoraco-abdominal organs is necessary to inform coverage requirements. However, existing methods of organ boundary identification are costly and time consuming, limiting widespread adoption for use on soldier populations. The aim of this study was to evaluate a novel method of using 3D organ models to identify essential organ boundaries from low dose planar X-rays and 3D external surface scans of the human torso. The results revealed that, while possible to reconstruct 3D organs using template 3D organ models placed over X-ray images, the boundary data (relating to the size and position of each organ) obtained from the reconstructed organs differed significantly from MRI organ data. The magnitude of difference varied between organs. The most accurate anatomical boundaries were the left, right, and inferior boundaries of the heart, and lateral boundaries for the liver and spleen. Visual inspection of the data demonstrated that 11 of 18 organ models were successfully integrated within the 3D space of the participant's surface scan. These results suggest that, if this method is further refined and evaluated, it has potential to be used as a tool for estimating body armour coverage requirements., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: This study was funded by the Defence Science and Technology Group, Department of Defence, Australia under a Defence Science Partnering Deed (reference number 10829). Sheridan Laing and Mark Jaffrey were employees of Defence Science and Technology Group, Department of Defence, Australia at the time the project was undertaken., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

To optimise fit and protection of body armour systems, knowledge of the location of thoracoabdominal organ boundaries is required. The aims of this study were (i) determine the effect of sex on essential and desirable thoracoabdominal organ boundaries, and (ii) compare essential thoracoabdominal organ boundaries with small and large hard ballistic plate sizes from the National Institute of Justice (NIJ) and determine if coverage requirements differ between sexes. 33 males and 33 females underwent supine magnetic resonance imaging of their thoracoabdominal organs. Male participants on average displayed more laterally and inferiorly positioned essential and desirable organ boundaries than females. Based on NIJ plate sizes, insufficient coverage of essential organs was identified for male and female participants. A greater range of body armour sizes and designs that better cater to the diverse anatomy of soldier populations is warranted, but must be considered in the context of ergonomic and performance implications., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: This study was funded by the Defence Science and Technology Group, Department of Defence, Australia under a Defence Science Partnering Deed (reference number 10829). Sheridan Laing and Mark Jaffrey were employees of Defence Science and Technology Group, Department of Defence, Australia at the time the project was undertaken., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Background: Attrition rate in new army recruits is higher than in incumbent troops. In the current study, we identified the risk factors for attrition due to injuries and physical fitness failure in recruit training. A variety of predictive models were attempted., Methods: This retrospective cohort included 19,769 Army soldiers of the Australian Defence Force receiving recruit training during a period from 2006 to 2011. Among them, 7692 reserve soldiers received a 28-day training course, and the remaining 12,077 full-time soldiers received an 80-day training course. Retrieved data included anthropometric measures, course-specific variables, injury, and physical fitness failure. Multivariate regression was used to develop a variety of models to predict the rate of attrition due to injuries and physical fitness failure. The area under the receiver operating characteristic curve was used to compare the performance of the models., Results: In the overall analysis that included both the 28-day and 80-day courses, the incidence of injury of any type was 27.8%. The 80-day course had a higher rate of injury if calculated per course (34.3% vs. 17.6% in the 28-day course), but lower number of injuries per person-year (1.56 vs. 2.29). Fitness test failure rate was significantly higher in the 28-day course (30.0% vs. 12.1%). The overall attrition rate was 5.2 and 5.0% in the 28-day and 80-day courses, respectively. Stress fracture was common in the 80-day course (n = 44) and rare in the 28-day course (n = 1). The areas under the receiver operating characteristic curves for the course-specific predictive models were relatively low (ranging from 0.51 to 0.69), consistent with "failed" to "poor" predictive accuracy. The course-combined models performed somewhat better than the course-specific models, with two models having AUC of 0.70 and 0.78, which are considered "fair" predictive accuracy., Conclusion: Attrition rate was similar between 28-day and 80-day courses. In comparison to the 80-day full course, the 28-day course had a lower rate of injury but a higher number of injuries per person-year and of fitness test failure. These findings suggest fitness level at the commencement of training is a critically important factor to consider when designing the course curriculum, particularly short courses.

When simulating or conducting land mine blast tests on armored vehicles to assess potential occupant injury, the preference is to use the Hybrid III anthropomorphic test device (ATD). In land blast events, neither the effect of body-borne equipment (BBE) on the ATD response nor the dynamic response index (DRI) is well understood. An experimental study was carried out using a drop tower test rig, with a rigid seat mounted on a carriage table undergoing average accelerations of 161 g and 232 g over 3 ms. A key aspect of the work looked at the various lumbar spine assemblies available for a Hybrid III ATD. These can result in different load cell orientations for the ATD which in turn can affect the load measurement in the vertical and horizontal planes. Thirty-two tests were carried out using two BBE mass conditions and three variations of ATDs. The latter were the Hybrid III with the curved (conventional) spine, the Hybrid III with the pedestrian (straight) spine, and the Federal Aviation Administration (FAA) Hybrid III which also has a straight spine. The results showed that the straight lumbar spine assemblies produced similar ATD responses in drop tower tests using a rigid seat. In contrast, the curved lumbar spine assembly generated a lower pelvis acceleration and a higher lumbar load than the straight lumbar spine assemblies. The maximum relative displacement of the lumbar spine occurred after the peak loading event, suggesting that the DRI is not suitable for assessing injury when the impact duration is short and an ATD is seated on a rigid seat on a drop tower. The peak vertical lumbar loads did not change with increasing BBE mass because the equipment mass effects did not become a factor during the peak loading event.