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Abstract
The development of inclusive equipment and clothing is a priority across national defence departments that are part of The Technical Cooperation Programme. As such, a collaborative effort has been established to inform the development of clothing and equipment for women. This invited review provides an overview of an ongoing collaborative project presented at the sixth International Congress on Soldiers Physical Performance. The purpose of this review was to summarise the outputs of scoping work conducted to inform the direction of future research programmes. The scoping work has recommended a framework, which includes improved objective metrics for assessment, standardised methods to characterise study participants and improved methods for characterising the system being evaluated. The longer-term research project aims to implement the framework so that the design of future equipment and clothing is optimised for all end users.
- Anatomy
- Physiology
- Musculoskeletal disorders
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WHAT IS ALREADY KNOWN ON THIS TOPIC
Many items of military clothing and equipment issued to women are unisex and do not account for the body shape and size of women. This leads to poor fit which has a detrimental impact on performance.
WHAT THIS STUDY ADDS
This review provides a framework for future evaluations of clothing and equipment.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
If the proposed framework is implemented, the evidence for more inclusive clothing and equipment will be strengthened, and actionable design requirements will be better specified.
Introduction
Women have long held visible and invisible roles in militaries across the world. Much of the operational body-worn clothing and individual equipment (CIE), issued to female soldiers does not account for a female body shape and size. In fact, much of the CIE issued and used by women is unisex, primarily tested on male soldiers, or specifically designed according to a man’s anthropometry. This leads to poor fitting CIE for women which increases discomfort, degrades task performance and leads to medical problems.1–4 Developing inclusive kit is now a priority for many nations, who are actively seeking to better represent population diversity across all roles.
In December 2022, a collaborative effort was initiated by nations that participate in The Technical Cooperation Programme (TTCP, which includes—Australia, Canada, New Zealand, the UK and the USA), a defence science organisation, under the Human Systems Performance—Land panel. The aims of this multiyear effort are to cohere research supporting the improvement of CIE for women; identify knowledge gaps; develop a prioritised plan to address these gaps and provide design/functional recommendations for the design, test and evaluation of future CIE.
The outputs of scoping work conducted in year 1 of the TTCP project were presented at the sixth International Congress on Soldiers Physical Performance. This invited review summarises the outputs of this scoping work.
Definitions
For the purpose of this project, CIE was defined as bodyborne equipment and clothing worn to protect and enable the soldier in military operations. Table 1 provides included and excluded items.
Items included and excluded in the definition of operational clothing and individual equipment
Current evidence base
There is a growing body of work examining CIE for women. To meet journal requirements, it was not possible to cite all literature which informed scoping work. As such, the search methodology and full bibliography are provided as Online supplemental file 1. Exploration of government and published literature indicates that body armour, load carriage and clothing have received the most attention; key findings for these areas are summarised here, with the full evidence base provided in a TTCP report.
Supplemental material
Body armour
Body armour was defined as ballistic and blast-protective CIE for the torso. These items are usually vests that cover the torso of the soldier with a carrier, a soft (textile based) armour insert to protect against fragmenting munitions, with smaller rigid ballistic plates positioned on the front, back and/or sides of the body. Plate coverage is intended to protect the most vital organs from small arms projectiles. Most systems incorporate load carriage or a way to directly attach pouches or pockets for readily-accessible combat supplies on the torso (e.g., munitions, hydration, compass, maps and communications control); the implications of load carriage are considered in the load carriage section.
The literature has addressed multiple research objectives, frequently from different perspectives. A variety of data collection methods were used, but the most frequent were surveys and focus groups to gather user opinion, fit assessments/anthropometric studies, range of motion assessments (for an indication of soldier movement restriction), three-dimensional (3D) scanning (to assess torso space claim or bulk), skin pressure measurement (to assess perceived discomfort objectively) and user trials measuring role-specific task performance and opinion (see Online supplemental file 1). Because many of the reports were the result of product development and testing, researchers sought to understand the acceptability of specific body armour systems or individual design features for women.2 5 Researchers also explored the performance and injury implications service women faced due to poorly fitting body armour systems.1 3 6 Additional efforts focused on anthropometrically centred design to improve the fit/performance of body armour; recommendations designed to improve the fit and function of body armour for women included reducing the size (length and width, coverage) of plates and soft armour, providing alternative sizing systems, consideration of curved plates and carrier construction modifications to improve sizing and adjustability (see Online supplemental file 1).
The importance of breast health is being increasingly acknowledged in military research, for example, the implications of wearing body armour on breast tissue.2 4 7 Coltman et al7 reported that women with medium-large breasts self-reported higher breast discomfort scores when wearing body armour than women with small breasts. There were also a higher number of self-reported breast injuries from wearing body armour in women with medium-large breasts compared with women with small breasts. Further, compatibility issues between the bra and body armour have been identified.2 4 Women who wore a padded or push-up bra reported lower percentages of discomfort and it was recognised that padding can improve comfort in certain circumstances.8 Alternative plate shapes for women have been explored, but further work is required to mitigate breast discomfort and injury risk with and without body armour (see Online supplemental file 1).
Load carriage
Load carriage was defined as a system used to carry additional supplies and equipment on the body (i.e., chest rig, harness, belt order and webbing). Several themes from the methodologies employed in load carriage research emerged.
There is evidence that discomfort1 9 and ratings of effort10 during load carriage tasks are greater in women compared with men. Greater foot and hip discomfort in women has also been observed.9 Armstrong et al1 reported a greater reduction in cognitive test accuracy during load carriage in female compared with male soldiers; the authors attributed this finding to poor fitting CIE that increased discomfort in women. Several recommendations to reduce discomfort in women were identified including: a need for adjustability; improvements to the general fit of equipment and the need for training at the time of issue (see Online supplemental file 1).
There is a large body of literature describing physiological and biomechanical responses to load carriage, but historically most studies have only included male participants. Research including women has explored the impact of load carriage on core temperature,11 muscle fatigue,10 12 cardiovascular10 12 13 and respiratory12 responses to load carriage, gait parameters,13–15 spatiotemporal, kinetic and kinematic variables13–16 and performance metrics.3 17 This literature has quantified the impact of load carriage on female physiology and biomechanics and highlights that women may be at increased risk of injury.6 18–21 However, differences in the research purpose and methods mean that translating this research to provide recommendations for the design of CIE is challenging. Load carriage has negative consequences for both men and women; it is unclear what sex-related attributes lead to the observed differences between men and women reported in the aforementioned studies.
Clothing
Clothing was defined as military field duty uniform. This focused primarily on combat shirts and combat trousers but given its female-specific nature, maternity clothing was also included. It is acknowledged that the majority of military clothing is available in a unisex design, with some militaries now providing female-specific alternatives to improve female fit (e.g., the ‘alternate fit’ for the New Zealand and Australian uniforms).
Various aspects of military clothing have been evaluated including acceptability/satisfaction,5 22 fit and sizing issues,5 and design recommendations (e.g., placement of pockets or the inclusion of an adjustable waistband)22 via surveys and user trials. Poor fit was identified as a larger issue for women than men,5 23 likely due to unisex designs. An influence of individual fit preference and the difference between objective technology-driven fit (e.g., 3D body scanning and fit mapping) and subjective fit (as perceived by the wearer) was also noted.23 24 One study employed fit mapping to quantify fit, accommodation rates and used this to produce updated sizing charts for size prediction.5 Government reports indicate that evaluations have included assessments of size, fit, mobility or range of motion, agility, comfort (physical and thermal), marksmanship, performance (e.g., in military tasks and obstacle courses), maintenance, durability, design, adjustability, bulk, weight, hindrance, aesthetics, colour, colourfastness, appearance when dry and wet, and integration with other layers of CIE.22 While several studies have focused on physical aspects (e.g., physical fit and comfort), a handful of studies have considered the emotional and psychological satisfaction too, recognising that these are linked to feelings of belongingness, confidence and empowerment.22
Other studies have taken an anthropometry approach to capture the variability in body shape and size and to improve uniform sizing and issuing.25–28 Several imaging technologies have been employed including two-dimensional body imaging24 and smartphone apps,23 with 3D body scanning becoming increasingly popular.25–28 A principal component analysis of 3D body scan data identified that waist circumference primarily defines overall female torso size, with chest-waist drop and waist-buttock drop both defining local torso shape.28 In an anthropometric characteristics cluster analysis based on 3D body scans, Kolose et al26 27 found that female clothing clusters were more variable and further apart compared with males. This supports findings from other reports that state different sizing systems are required for men and women.22 25
Breast support is a critical item of CIE. While commercial-off-the-shelf sports bras are not designed for military use, they are commonly worn during military activities.7 29 Research has investigated the incidence and severity of breast pain, sports bra use and issues in military recruit populations.29 US government reports highlight efforts to develop an ‘Army Tactical Brassiere’—a sports bra for military physical training activities (see Online supplemental file 1). Further research is needed to quantify the functional requirements of breast support specific to the demands of military activities, to understand whether the styles and selection of bras currently issued in the military are appropriate.29 To reduce bra fit issues, professional bra fitting and breast health education during basic training is recommended.29
Discussion
Female inclusive or female-specific?
This review highlights an increase in the number of publications considering women in the design of CIE in recent years. This increase reflects improved understanding of the importance of human factors assessment, as well as greater awareness of the impact that poor fitting CIE has on women. Although the project described in this manuscript is focused on providing recommendations for the design of CIE for women, the authors wish to acknowledge that CIE design needs to be improved for all service personnel.
It is not always the case that female-specific CIE which is designed specifically for women is required. Female-inclusive equipment which accommodates the requirements of the entire population may be favourable. Indeed, some of the CIE modifications implemented for women may be beneficial to certain men and may be more widely accepted if it does not single out a specific group. For example, the Canadian Army field or combat uniform will halve the increments in circumference and length between sizes (from 4” to 2”, allowing improved fit for those currently between sizes) and will offer two garment styles (e.g., contoured or not contoured) with gender-neutral naming conventions that anyone can choose to wear.
For female-inclusive CIE in particular, there is some evidence to suggest that sizes typically used by females are not always readily available through traditional supply chains, and/or personnel issuing CIE do not always have the training required to provide the best fit. Offering reasonable adjustments or even custom designs may be required for some individuals. For example, UK body armour issue incorporates requests for additional tailoring when sizing is inadequate. Body armour sizing is considered inadequate if the level of protection provided is compromised due to poor fit or if the armour is deemed to limit task performance beyond acceptable levels.
Research framework for future work
Despite an increase in the number of studies which have included women, there is still limited evidence available to provide specific recommendations for the design of CIE for female soldiers. Constraints placed on researchers (including time, access to participants, and integration of repeatable and reliable metrics with the military environment) have limited the scope of current research. Further, much of the research available has been designed to evaluate specific items of CIE rather than improve CIE design for the future. As such, in September 2023, the authors hosted a workshop which brought together experts from within TTCP defence organisations to provide recommendations to inform the development of future research programmes. These recommendations are summarised as a framework in Figure 1 and are discussed below.
Summary of recommendations to improve the design of clothing and individual equipment for a diverse population. Image created using Mindthegraph.com.
Standardised assessment metrics and methods
Previous work has used a variety of assessment metrics to characterise study participants, CIE items being evaluated and the impact of CIE on the user and task performance. Variation in the metrics used and experimental design were observed. As such, it is recommended that defence organisations invest in a collaborative effort to develop and standardise objective metrics and methods that demonstrate acceptable validity and repeatability in the military environment. A defence lead for this task will ensure that resulting metrics and methods are not biased towards a specific manufacturer or a specific country’s CIE designs. All assessment methods and metrics will have limitations, but if they are developed coherently, the impact of these limitations will be minimised.
CIE assessments should consider the short-term and long-term effects of the items on the wearer. Performance should be evaluated in operationally relevant environments,17 with the inclusion and consideration of multiple operational stressors. Developing standardised methods and metrics is not an insurmountable task. For example, methods to assess agility and mobility using a simulated combat mobility course that several countries have adopted have been achieved (see Online supplemental file 1 for unpublished government studies). While the vast majority of these standard methods have been used in studies with men, there is increasing effort to increase the representation of women.
Performance thresholds
Following the development of standardised metrics, researchers should develop acceptable thresholds for these metrics for both men and women that represent the clothing and equipment being worn as well as the operating environment. For example, methods for assessing the skin contact pressure imposed by body armour and load carriage have been defined alongside thresholds that skin contact pressure should not exceed.30 Physical and virtual human models have been and are being developed to assess many important aspects of CIE including thermal properties11 and skin pressures under armour or loads30 to allow more rapid, efficient, human out-of-the-loop testing of equipment. These models will increase the number of prototypes and design iterations that can be objectively evaluated before resource-intensive user trials are conducted.30 The limitations associated with models must be fully understood and better articulated to support with interpretation of resulting data. Models must be improved for diversity representation and validated with human-based test data.
Characterising experimental participants
It is essential that future assessments be conducted with both men and women to optimise the health and performance of service personnel and to identify those who may be at greater risk and require additional provision (e.g., individual adjustments or custom solutions). It is recognised that access to female service personnel and other demographics may be limited due to their smaller numbers within military forces. Strategies to deal with this challenge should be explored including standardising how studies characterise experimental participants so that they can be compared with target populations. Guidance should be provided which articulates when civilians can be used to represent military populations noting that civilians are not representative of a more experienced military population; different levels of experience may be required for some outcome measures within a military population.
Several studies have emphasised the need for female-specific CIE and more sizes to better accommodate women.22 26 27 As seen by Li and Mitchell28 and Kolose et al,26 27 torso shape and sizing systems could be developed using 3D body scanning anthropometry data and machine learning algorithms. This can be adapted to different populations (defined by country of origin, race, etc) to improve fit.27 28 It is critical to build a comprehensive data pool that encompasses a range of ages and morphotypes within the anthropometry database.23 Further development of machine learning and training of algorithms will improve CIE size predictions.23 Industrial standardisation of size codes across nations would benefit militaries and size allocation algorithms.23
Characterising the system being evaluated
Standardised objective metrics which define the properties of the ensemble (e.g., mass, bulk, distribution of mass and bulk, stiffness) will ensure that study data can be compared and combined. These data will enable researchers to determine and prioritise which CIE parameters matter most in terms of enabling improved mobility, lethality and survivability. These metrics would also help identify which design interventions work best, would standardise CIE for improved interoperability and enable more efficient testing of alternative designs by all stakeholders.
Novel solutions
Novel solutions that incorporate lighter-weight, more flexible, less bulky material solutions are required that enable more contoured fit, improved comfort, better integration and optimised task performance while maintaining technical performance (i.e., protection levels). Adjustability to achieve conformal fit is of particular importance for women due to the wide range of breast sizes and shapes. These material improvements are likely to improve the protection, performance and satisfaction of the entire soldier population.
Summary
This work has identified knowledge and capability gaps that need to be addressed so that defence organisations can provide CIE that is optimised for women. This will involve defining test metrics and assessment methods that should be applied to future research and evaluations of CIE. Future studies should use these metrics and methods to fully characterise the experimental participants and system being evaluated to enable data sharing across research groups. Novel solutions should continue to be explored so that service personnel can benefit from advances in technology as soon as they emerge. The longer-term TTCP project seeks to address these gaps, working in collaboration with industry and academia.
The results of this scoping work should be considered in light of a few limitations. The authors acknowledge that there are important considerations for women associated with the excluded CIE items, but recommendations for how these items should be considered in future work will be provided as part of the wider TTCP effort. This work considered biological and physiological factors associated with female sex but did not consider the role of gender and CIE design. Finally, the scope of the literature search was limited to the last 15 years. It is acknowledged that for some items of CIE (e.g., chemical biological, radiological and nuclear, personal protective equipment) informative studies may have been excluded. This limitation will be addressed through the longer-term TTCP project.
Ethics statements
Patient consent for publication
Acknowledgments
The authors would like to thank members of TTCP HUM JP1 for their support with setting up this project. This includes Dr Mike LaFiandra, Dr Mark Patterson, Mr Adam Dooley, Dr Caroline Mahoney and Dr Justin Hollands. This review would not have been possible without the support of defence researchers who assisted with the literature searching: Dr Katrina Hinde, Dr. Hyegjoo Choi-Rokas, Ms. Linda DeSimone and Dr Lauren Keaney.
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
X @nic_c_armstrong
Contributors NA and LB conceived the project and developed the plan. SR, AF, KMG and SS conducted the literature review. NA, SR, KMG, KBM, AF and LB wrote sections of the manuscript. All authors reviewed the manuscript.
Funding This work was funded by the UK Ministry of Defence, through the Dstl Human Augmentation project.
Competing interests None declared.
Provenance and peer review Commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.