Article Text
Abstract
Introduction OSPREY 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 on women in ground close combat roles throughout the UK’s Armed Forces was lifted. In anticipation of this, work has been ongoing to prepare future ballistic protection programmes for a potential increase in the number of female users.
Method A human factors questionnaire was provided to 150 female users of OSPREY body armour to complete while on combat operations in Afghanistan. The questionnaire asked the users to rate the comfort of their OSPREY body armour along with their ability to carry out basic tasks. Other background data such as size of body armour worn and bra size were also collected for the analysis.
Results The female participants reported various types of discomfort when wearing their OSPREY body armour, with 135 instances of discomfort experienced in the hip region, for example. Challenges were reported in the ability to carry out basic movements, with the tasks rated on a Likert scale as difficult or very difficult by between 29% and 59% of participants. In addition, a restriction in ability to access personal equipment worn on the person (including pouches, trouser pockets) was commented on by 39% of participants.
Conclusions Female users reported challenges relating to the fit and function of OSPREY body armour. The VIRTUS body armour system for UK Armed Forces Personnel has already addressed many of the reported issues with OSPREY. Further optimisation for VIRTUS with regard to female users is planned and includes sizing of ballistic hard plates.
- ballistic protection
- female
- anthropometric
- sizing
- fit
Data availability statement
Data are available upon reasonable request.
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Introduction
In 2012, Defence Equipment & Support supported a student project looking at the design and development of female fit body armour.1 This included a questionnaire aimed at capturing any issues experienced by female Armed Forces personnel wearing OSPREY body armour (see supplementary file - online only). The questionnaire was sent to female users across Afghanistan in November 2012 and returned in January 2013. This voluntary, anonymous questionnaire received responses from 150 female users across multiple locations and units (at least 15 and 35, respectively). At the time of the questionnaire, OSPREY Mk IVa body armour was the issued equipment, and it is still in service today (figure 1). OSPREY’s sizing is based on the user’s stature (height) and chest circumference.2
Supplemental material
The questionnaire covered three main areas: basic information about the participant (eg, height, bra size, OSPREY size worn), any discomfort experienced and a functionality assessment. Functional tasks were developed as part of the original student project, aimed at representing functional movements commonly required when wearing body armour. At the end of the questionnaire, a ‘free field’ was provided, allowing the participant to comment on aspects of the armour’s fit and functionality not covered elsewhere.
In 2014, the Secretary of State for Defence welcomed the opening of ground close combat roles in the Armed Forces to women, following the results of a review analysing the impact of such a move on combat effectiveness.3 This instigated a period of deeper investigation into the effects of the physiological demands on women, culminating in the opening of ground close combat roles to women in 2016.4 Between 2016 and 2018, these roles were opened incrementally based on their associated physiological demands, and now all roles in the UK’s Armed Forces are open to women.5
In 2016, the initial questionnaire responses received were re-analysed. The task was to use the existing data to identify and analyse common issues experienced by female users with the fit of OSPREY body armour. The results would inform new ballistic protection projects, to prepare for a potential increase in the number of female users.
Since the initial work was conducted, the percentage of women in the Armed Forces has increased. In October 2012, the number of women in the Armed Forces was 17 060 (9.7%). In April 2019, the number was 15 340 (10.6%) which, despite the decrease in overall numbers of women in the armed forces, is part of a percentage increase which has not recently shown any signs of slowing down.6 It is imperative that any sex-specific issues with body armour are therefore identified, captured and subsequently addressed in any new ballistic protection projects. The VIRTUS body armour system for UK Armed Forces Personnel (introduced in 2015) has already addressed some of the reported issues and further work is ongoing.7
Methods
Questionnaire analysis
The initial paper-based questionnaire responses were collated re-analysed using new methods (described in turn).
Suitability of fit was determined for participants who specified their body armour size, bra size and stature. First, bra size was converted into chest circumference. The participant’s chest circumference and stature were then compared with the size of armour worn using the OSPREY sizing chart.2 Subsequently, this comparison was classified to indicate whether the participant was wearing the correct size of armour, using novel sizing descriptors developed for this study (table 1).
Overall user comfort was assessed based on a five-point Likert Scale, with the option of pinpointing any areas of discomfort and associated mechanisms on a diagram (figure 2). To assess of the effect of sizing on the comfort of the armour, these data were compared with the participant’s sizing descriptors.
Participants were asked to assess their ability to carry out basic tasks while wearing OSPREY body armour also using a five-point Likert Scale, with associated reasoning captured in comments. These data were compared with the participant’s sizing descriptor to identify any relationships.
All comments in the questionnaire were assessed for commonality and formed into basic groupings based on trends in the responses, to capture commonly reported issues.
Anthropometric comparisons
To contextualise the results of the questionnaires, male and female forms were compared using data from the 1988 US Army Anthropometric Survey.8
Male and female populations were filtered by stature to align with the OSPREY sizing chart, enabling comparison of the following size brackets:
From (including) 1.60 m up to (not including) 1.70 m.
From (including) 1.70 m up to (not including) 1.80 m.
Three areas were assessed (evaluating the percentage difference between the fifth, 25th, 50th, 75th and 95th female percentiles and their respective male percentiles). The first was chest fit, including chest depth, chest height, chest circumference (below bust), chest circumference (over bust) and chest breadth. The second was shoulders and neck, including neck circumference (at base), arm circumference (at axilla) and bi-acromial breadth. The third was waist and hip, including waist circumference, difference in height between the waist and hip, abdominal extension depth when sitting, waist height, hip breadth and hip breadth when sitting.
Results
Questionnaire analysis
Statures of the participants were plotted on a graph and the distribution is shown in figure 3. The mean stature of the participants was 1.66 m.
Table 2 shows the results for the assessment of fit (using the novel sizing descriptors) for the 73% participants who had provided the required information. This demonstrated that out of these responses, 85% had the correct fit around the chest, while 44% had the correct fit for stature. The combined chest and stature fit descriptors per participant showed that 38% had correctly fitted armour and 36% had armour correctly fitted around the chest, but too big for their stature.
In terms of overall comfort of OSPREY body armour, 37% found the armour uncomfortable/very uncomfortable, 47% were neither uncomfortable nor comfortable and 16% were comfortable (table 3).
The frequencies of pinpointed areas of discomfort were plotted against location (on the armour) in table 4. Three main areas of discomfort are visible: hips (61%), shoulders (51%) and chest (37%). Sizing descriptors were also plotted against discomfort mechanisms for the main areas of discomfort, which showed discomfort reported across all sizing descriptors.
For the functionality assessment, frequency of response was plotted against the tasks from the questionnaire (table 5).
In the comment analysis, frequency of comment occurrence was plotted against grouping (figure 4). Duplication of comments by a participant was filtered in the analysis by removing identifiable double-reporting, to prevent misleading results.
Anthropometric comparisons
The pertinent data from the 1988 US Army Anthropometric Survey8 showed that for females, chest circumference (over bust) was 4%–6% smaller than for males. Chest depth ranged from 1% shallower to 4% bigger. Chest breadth was 9%–11% smaller, contributing to the smaller overall circumference (over bust). Chest circumference (below bust) was 12%–16% smaller and chest height ranged from 3% smaller to 1% bigger.
Neck circumference at the neck base for females was 12%–15% smaller compared with males. Arm circumference at the axilla was 8%–12% smaller and the bi-acromial breadth was 4%–7% smaller for females.
Waist circumferences for females were 9%–12% smaller, with waist height varying from 2% smaller to 3% bigger. Abdominal extension depth was 3%–8% smaller. Hip breadth of females in this dataset was 3%–7% bigger; however when sitting, it increased further to 6%–11% bigger. The distance between the hips and waist was 7%–15% smaller.
Discussion
Questionnaire analysis
The stature distribution of the participants is key, with 77% of participants measuring between 1.53 and 1.70 m and occupying smallest sizing bracket of the OSPREY sizing chart (‘up to 170 cm’, table 1), this independently shows that the current sizing regime of OSPREY is unsuitable for females.
From the stature distribution, it could be inferred that females require shorter body armour than males, assuming the sizing chart is representative for males and stature is a valid measure. However, a recent study found that stature was poorly correlated to the medical coverage requirement for body armour, with torso height (suprasternal notch to iliac crest) recommended as the measure for determining coverage and sizing.9 Data on torso length require collection to enable this comparison.
The sizing analysis (table 2) suggested that achieving a chest fit was more successful than achieving a stature fit, with 82% of females with armour that was too long having the correct fit around the chest. A possible reason for this is, for example, a prioritisation of chest fit over stature fit by the user, ‘going up’ a size in stature to achieve a better chest fit. There is anecdotal evidence of this, but it cannot be proven using the available questionnaire data.
The hips, shoulders and chest are the main areas of reported discomfort (table 4). There were no obvious links between sizing descriptors and discomfort, with many users reporting discomfort despite having been sized correctly.
Regarding discomfort at the hips, the proximity between the edges of body armour and the borders of other items of clothing/equipment could cause ‘pinching’. When the wearer bends from the waist (for example), the edges of worn equipment come together and, if in proximity, may pinch the wearers skin. 41% of participants with armour too big for their stature may have experienced this, with incorrect sizing or integration issues being the most likely causes. The terms ‘chafing’ and ‘rubbing’ were grouped into a single point due to potential issues with differentiation. Either of these instances can occur when armour held close to the body does not move with the body, causing friction between the user’s skin and clothing under the armour. It is more likely when armour does not fit well, as it may contact areas of the body it should not. Underpinning issues could be the sizing or design of the armour. Some of the comments grouped into ‘rubs hips when moving/tabbing and stationary’, ‘difficult to twist (and rubs hips)’ and ‘not fitted to female build’ support this hypothesis.
Discomfort at the shoulders mostly consisted of ‘pressure’, which is naturally created by the mass of the armour; however, this can be exacerbated by poor fit and pressure points (seams, etc). Where shoulder padding sits too far out on a user‘s shoulders, it can cause unnecessary discomfort and restriction. Comment groups such as ‘restricts lifting arms/movement’, ‘shoulder padding too wide’, ‘significant weight’ and ‘not fitted to female build’ support this hypothesis.
For discomfort at the chest, ‘pressure’ and ‘squashing’ were grouped into a single point as both terms can be interpreted interchangeably. This is likely to be experienced where the circumference of the armour is too small, or the depth of the armour (fabric between the front and back plates) is too shallow. Comments in the groups ‘squashes chest/breasts, restricts breathing’, ‘cannot get body armour close to body’, ‘cannot reach hips/pouches on armour/trouser pockets’ and ‘armhole openings too big’ support this hypothesis.
The functionality tasks were assessed using a Likert scale, and a median Likert value (mLv) was used to indicate trends. Functionality assessments while standing and sitting are discussed in the following two paragraphs.
First, looking at the standing position, ‘picking up a lightweight item from the floor’ (mLv 3) required bending at the waist, which could have been negatively affected by the ‘one size fits all’ OSPREY plate contacting the top of the legs while bending, or by the carrier being too long for the participant. The task ‘raise your hands above your head’ (mLv 3) was found difficult by 30% of participants. This may have been caused by smaller females finding the shoulder padding too wide, with any protrusion past the acromion likely to cause movement restriction (reflected in the comments). Weight on the shoulders could also have impacted this, particularly if the weight was not distributed away from articulating joints. For ‘touching right shoulder with left hand’ and ‘touching left shoulder with right hand’ (mLv 3), 29% and 30%, respectively, found it difficult or worse, despite the fact that this should have been a simple movement. It is hypothesised that as the plate sits further out from the body for females it could cause an obstruction; however, the plate and carrier may also be too wide at the shoulders for those of a small stature. The movements ‘touching right hip with left hand’ and ‘touching left hip with right hand’ (mLv 4) are bigger movements than reaching opposite shoulders and the responses reflected this. Most responses (56% and 56% of responses, respectively) were reported as difficult or very difficult. These movements are commonly required in combat and the difficulties are likely to be due to the same reasons as the previous task.
In the sitting position, for ‘touching right ankle with right hand’ and ‘touching left ankle with left hand’ (mLv 4), articulation at the waist is required, with bending of the upper body and mobility of the arms. The fact that only 23% and 22% of responses, respectively, were reported as easy and above, with 47% and 48% reporting sitting as difficult or very difficult, reflected that the armour restricted mobility for females in its current form. For ‘twisting chest approx. 90 degrees to the left’ and ‘twisting chest approx. 90 degrees to the right’ (mLv 4), twisting was likely to be a challenge with rigid plates inserted in the soft armour vest, and this was reflected in the responses. 50% and 51% of participants, respectively, found this difficult or worse.
Evaluating the comments and the frequency of comment groupings (figure 4) provided further insights into the fit of the armour. It was possible to group these comments further depending on the issues investigated; and several groupings stood out. Starting with the grouping ‘cannot reach hips/pouches on armour/pockets’, 39% of the participants commented on this, and items required for combat are typically stored in these locations. The mLv of 4 for ‘touching right hip with left hand’ and ‘touching left hip with right hand’ provides further weight to the comments and suggests it was a common issue for the user. Moving to the groups ‘top of legs cut into/pressured when sitting/bending’, ‘body armour rising when sitting’ and ‘difficult to bend over’, the comments point to body armour being too long in the torso, causing problems with articulation at the waist. Finally, the groups ‘rubs hips when moving (running/tabbing) and stationary’, ‘difficult to twist (and rubs hips)’ suggest that body armour was not moving with the body and was in reasonably close contact with the hips, also tying in with further comment groups, ‘does not move with body’, ‘inflexible’ and ‘not fitted to female build’.
Anthropometric comparisons
The US Army anthropometric data showed that female chest circumferences were, on average, smaller than males.8 This may be due to a reduction in the breadth of female chests (9% to 11%), while being relatively unaffected by depth, as female chests were on average slightly deeper than male chests (from 1% shallower to 4% deeper). This difference in anthropometric form in the chest suggests the OSPREY soft armour vests were too wide for females while also not being sufficiently deep. This aligns with difficulties participants reported in reaching their hips/pouches on armour/pockets, as it caused a restriction when reaching across the body. It also aligns with the comment group ‘squashes chest/breasts, restricts breathing’ and table 4, which shows that 37% of the participants highlighted discomfort in this area.
Female neck circumference (at the base) being 12%–15% smaller could suggest that the armour is likely to ‘sit’ differently around the neck opening and potentially move around more for females. This could lead to discomfort if the armour moved off-centre and distributed weight unevenly. With bi-acromial breadth measuring 4%–7% smaller for females, the armour is more likely to overlap the acromion, restricting the user from lifting their arms. Comments such as ‘restricts lifting arms/movement’ reflect this. 51% of the participants commented on pressure in the shoulder region (table 4), further suggesting these differences may be important; however, it could also be based on the ratio of armour mass to bodyweight, which is potentially less advantageous for females than for males.10 Reduced arm circumference at the axilla (8%–12%) results in larger arm holes for females. This is reflected in comments under ‘arm hole openings too big’, noting not everyone who experienced the issue would have reported it, as it was not directly asked.
With female waists measuring 9%–12% smaller, hip breadth 3%–11% bigger and the distance between them being 7%–15% smaller, there is a large difference in anthropometry in this region. This could cause problems fitting OSPREY armour around the midriff while avoiding rubbing/chafing issues. This is strongly reflected in table 4 and in the comments ‘rubs hips when moving (running/tabbing) and stationary’ and ‘difficult to twist (and rubs hips)’, with further comments also potentially linked to this.
Although the US Army Anthropometric Survey was not fully representative of the UK military population, it included 1774 males and 2208 females and therefore provided an initial indication of sex-specific reasons behind discomfort/functionality issues when wearing the OSPREY armour.
Recommendations
This study highlights the need for further work to identify male versus female anthropometric differences (relevant to body armour fit) using UK Armed Forces data, to inform any improvements to the fit, comfort and functionality for female users. Further to this, it is recommended that future anthropometric studies on UK Armed Forces personnel include the measurement of both male and female torso length (suprasternal notch to iliac crest).
A sizing system based on torso length should be used to optimise the fit of body armour for females (and males), akin to the new VIRTUS body armour and load carriage system for UK Armed Forces personnel (which uses ‘torso size’ to fit the soft armour vest). This study should be repeated with male and female users of the new VIRTUS body armour and load carriage system to ascertain if using the ‘torso’ size has had any impact on the fit and other issues described in this study, which would also simultaneously enable a sex-specific comparison.
Limitations
As this survey was completed on a voluntary basis and distributed remotely, the actual number of females it reached is unknown; therefore, the response rate is unknown. It was not possible to determine what type of activities each participant typically undertook in their body armour, or the level of exposure to these activities from the available data. In future studies, capturing data on response rate, on the participant’s role and how often the participants use their body armour as part of the questionnaires could address some of the limitations. Further to this, as a review of previous work was not included as part of this study, a future study collating and comparing existing work would be beneficial.
Conclusions
The results of the analysis demonstrate that just over a third of the participants found the OSPREY body armour uncomfortable, with up to 61% of participants reporting discomfort such as chafing at the hips, pressure on the shoulders and squashing of the chest. This was not linked to whether the armour was fitted correctly, suggesting that the main sources of discomfort were related to differences in male and female anthropometry.
In terms of functionality, challenges were reported in the female user’s ability to carry out functional movements; the main sources of difficulty were movements requiring the user to touch their left hip with their right hand and vice versa. 56% of participants reported it as difficult/very difficult, with a further 39% of the participants voluntarily commenting on difficulties accessing equipment mounted on their hips, pouches on their armour and pockets in their trousers. Functionally, twisting, bending and lifting movements were also reported to be difficult.
Initial analysis into differences between the male and female anthropometry suggested that sex has a meaningful impact on body armour fit.
Data availability statement
Data are available upon reasonable request.
Ethics statements
Patient consent for publication
Ethics approval
No ethical approval was required. The survey was voluntary and anonymous, distributed to units with female service personnel by the Scientific Advisor (SCIAD) in Camp Bastion, Afghanistan at the time.
Acknowledgments
The authors would like to thank Lieutenant Colonel Johno Breeze for his advice during the preparation of this manuscript.
Footnotes
Contributors EL conceived the idea and supervised the work. JE planned and implemented the survey. JD collated the results, performed the analysis and wrote the manuscript with guidance from EL. All authors discussed the results and commented on the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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