Abstract
Exercise and participation in sport can have physical, psychological, and social benefits to persons with disabilities. The high cost ($5,000 to $12,000 USD) and long lead times of sport wheelchairs, however, is a barrier to participation. The objective of this study was to develop an affordable kirigami inspired rugby wheelchair made from sheet metal instead of tubes. Three prototypes of varying seat widths were designed, fabricated, and evaluated by 11 participants. Participants performed common drills in the prototype that best matched their hip width, and each provided feedback via a structured interview. The participants reported overall favorable reviews and cited the adjustability, repairability, and implications of this wheelchair on decreasing the barrier of entry to sport as its best features. Participants also identified areas for improvement, such as seat material and caster size. Future study should examine safety, durability, and performance during training and competition scenarios.
Introduction
Persons with disabilities (PwD) are two times as likely to be physically inactive compared to those without disabilities.1,2 Sedentary behavior has been linked to an increased risk of developing cardiovascular, metabolic, and musculoskeletal diseases, as well as negative psychological and social outcomes.3,4 One way that many people choose to participate in physical activity and combat sedentary behavior is via sport.
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Although the benefits of sport among PwD are extensive and well documented,6–8 numerous barriers to participation exist.9–12 For example, high costs and limited access to adaptive equipment creates a high barrier to entry.13–15 Rugby wheelchairs are particularly expensive, with base model frames starting at $5,000 USD and full rugby wheelchairs often costing $8,000 to $12,000 USD. This high cost is due to the tubular design, custom measurements, and skilled labor necessary to complete the large number of complex welds on all the tubular structures included to allow a rugby wheelchair to withstand the impacts of the sport.16,17 A typical offensive rugby wheelchair is shown in Figure 1. Standard tubular rugby wheelchair.
Given current building techniques and skilled labor required to produce rugby wheelchairs, cost reductions are unlikely to emerge in the future without disruption of the design and fabrication processes. 18 Consequently, new design approaches are warranted. One way to potentially reduce the cost and manufacturing time of rugby wheelchairs is to utilize kirigami engineering design and manufacturing. Kirigami is the ancient Japanese art of paper cutting and folding, which now serves as the inspiration for many advanced engineering designs. 19 The act of cutting a flat material allows for the creation of many shapes, and folding the material adds rigidity and form to the structure, enabling a lightweight structure to hold many times its own weight. 20 This design concept can be applied to sheet metal which can be easily cut and bent into shape. In the context of building a wheelchair, sheet metal parts can be more easily and inexpensively customized and manufactured, and can be assembled using rivets, spots welds, nuts, and bolts instead of the complex welding configurations needed for tubular wheelchairs. A lower manufacturing complexity and cost could allow for standard and customized rugby wheelchairs to be sold at a much lower price ($1000-$2000 USD) without compromising quality. Thus, more people may be able to access adapted sport and reap the associated benefits.
Objectives
The objective of this research was to design and fabricate a kirigami-inspired rugby wheelchair prototype and evaluate it through user testing to gather feedback, allowing for future improvements on the concept and design.
Basis of need
Historically, the literature examining wheelchair rugby has focused on performance analysis, propulsion biomechanics, benefits and barriers to participation,21–25 and customization for single use optimization.26,27 However, there is a dearth of literature exploring designs alternatives targeting efficient customization and cost reduction. The only published design utilizes an approach of large-diameter thin-wall tubing, but the design was only evaluated by one user. 28 There has been no literature utilizing kirigami engineering or sheet metal design in the wheelchair industry.
Given the documented benefits of sports participation and barriers to entry, a lower-cost entry level rugby wheelchair could offer more individuals participation opportunities and grow the sport globally.
Design
Prior to modeling the Kirigami rugby wheelchair (KRuW), design criteria were established in collaboration with an experienced wheelchair rugby player (n=1) who provided insight and feedback on important aspects of the design. Additionally, other individuals with experience playing adaptive sports (n=2) and designing adaptive sports equipment (n=3) were involved in developing design criteria and providing feedback through the design process. While these initial design criteria are largely qualitative as most will be measured by subjective feedback from participants, the criteria for future design iterations will be revised with more specificity to make them quantitatively measurable.
Criteria 1: Affordable to manufacture
The KRuW should reduce costs by employing a kirigami sheet metal manufacturing approach, thereby avoiding the need for seam welding in the assembly process.
Criteria 2: Customizable
To allow for ergonomic seating and favorable propulsion biomechanics for the user, the following parameters should be customizable on the design: Seat Width, Seat Depth, Front Seat Height, Rear Seat Height, and Rear Axle Position.
Criteria 3: Allow the user to secure themselves to the chair
To maintain a secure user wheelchair interface and prevent injury during collisions, the design should feature straps or belts that can secure the waist/hips and the feet to keep the user secured in the KRuW.
Criteria 4: Safe transfers
To prevent falls/injury during transfers, users should be satisfied with the ease and safety of transfers to/from the KRuW.
Criteria 5: Lightweight
To allow for efficient propulsion and ease of transportation, the KRuW should weigh less than 50 lbs (22.7 kg).
Criteria 6: Maneuverability
Users should be satisfied with the maneuverability of the KRuW while pushing forwards, backwards, and turning.
Criteria 7: Compliant with wheelchair rugby rules
World Wheelchair Rugby (WWR) has published specifications and restrictions on suitable/legal wheelchair features for competition. 29 The KRuW should comply with each of the specifications to allow it to be used in competitive play.
Criteria 8: Versatility
To allow participants of varying levels of ability to participate in wheelchair rugby, the KRuW should have variations that allow for both offensive and defensive play. The suitability of the KRuW for offensive and defensive play will be noted.
Criteria 9: Supports the weight of the user
The KRuW should dynamically support at least a 275 lb (125 kg) user without structural failure during practice or game dynamic loading to align with the weight capacities of rugby wheelchairs that are currently on the market.30,31
Criteria 10: Durability
The KRuW should be durable enough to survive the collisions and abuse typical in wheelchair rugby without breaking or deforming in a way that would impact safety, performance, or compliance with the WWR chair specifications. Contact components of the KRuW should be repairable or replaceable.
Design methods
After establishing the design criteria, a sheet metal KRuW was designed using SolidWorks, a Computer Aided Design (CAD) software.
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At this phase, the frame design can be customized to a user’s key wheelchair dimensions including seat width, seat depth, front seat height, rear seat height, and rear axle position. While customizable to specific dimensions, these dimensions are fixed and not adjustable once the frame is fabricated. The sheet metal frame model is shown in Figure 2, and the full KRuW model concept is shown in Figure 3. KRuW CAD model – sheet metal frame only. KRuW CAD model – full assembly.
Key design features
The KRuW was designed with a solid seat pan and a footrest cavity that extends below the flat bottom of the frame. The front bumper is reinforced with a thicker sheet metal strip attached to a tubular component which is intended to receive the impacts of collisions with other chairs. This front bumper attachment is designed to be removeable and replaceable if it should get broken or damaged to an extent that makes it unsuitable for further play. This replaceable bumper is a novel feature that is not commonly represented in rugby wheelchairs on the market. The front and rear casters and forks are bolted in bearing stacks within machined aluminum parts that are mounted to the sheet metal of the frame. These would be standard across all frame types and sizes. The backrest posts are bolted to the side of the KRuW frame using slots on a sheet metal bracket along with slots on the sheet metal side guards. These slots allow the backrest to be adjusted forward and backward, thus altering the seat depth and center of gravity. Tubular structures attach from under the seat pan to the top of the front bumper. These structures reinforce the frame, keep the user’s legs contained, and provide an area for the user to grab and put weight on during transfers. Most of the sheet metal parts are designed with overlapping flanges featuring pre-cut holes incorporated into the design drawings and laser cutting paths to ease the assembly using 1/8” (3.2 mm) pop rivets that allow for easy alignment during fabrication.
Sheet metal fabrication & assembly
To fabricate a KRuW prototype, the sheet metal parts were tightly nested for minimal waste material using post-processing software and cut from 6061-T6 aluminum sheet metal on a laser (Mazak Space Gear-U44) with a 4 foot by 4 foot (1.2 meter by 1.2 meter) cutting area. Software was used to optimize the cutting path for minimal time without warping or unintended burn through or scaring of the sheet metal. Prior to bending the parts, the press brake was programmed using software (SigmaBEND/AP X1 by AutoPol) that determines the ideal tooling, bend order, and backstop positions for each part. The resulting program was used to run an advanced CNC press brake (SafanDarley E-Brake 80T Ultra) that guides the user through setting up the tooling and aligning each sheet metal piece with the backstops to complete all the bends. The sheet metal KRuW parts are shown before and after bending in Figure 4. Flat sheet metal KRW parts after laser cutting (left) and bent sheet metal parts after press brake operations (right).
The bent sheet metal parts were assembled using aluminum and steel pop rivets and a cordless rivet gun. The resulting sheet metal KRuW frame assembly is shown in Figure 5 below. Sheet metal frame parts assembled using pop rivets holes which were pre-cut with laser to ensure proper alignment during assembly.
Additional fabrication processes
The axle receivers, caster bearing housings, and backrest tubes were machined from aluminum. The front tubes and bumper tube were bent using a CNC tubing bender and then the mounting holes were drilled by hand in the resulting bent aluminum tubes. In the future these could be incorporated into the design model and laser cut into the tubing. While the design still incorporates tubular parts along with other non-sheet metal machined parts, the parts are not welded directly to the frame. As a result, these could be standardized, mass produced parts that are manufactured cost effectively and then easily attached to the sheet metal wheelchair with nuts and bolts. In a future iteration, more off-the-shelf parts could be used to reduce cost and improve repairability. The sheet metal parts were powder coated to improve the aesthetic appeal, and then all of the machined and tubular parts were assembled and attached to the KRuW using nuts, bolts, and rivets.
Preparation for user testing
In preparation for user testing, three KRuWs were fabricated (Figure 6). The KRuWs were identical in dimensions except for the seat width, which ranged from 14 inches (36 cm) to 18 inches (46 cm) to accommodate a range of users. Adjustable-tension upholstery was incorporated on the backrests, flat closed cell foam cushions were placed on the seats, and ratchet straps (Sportaid, Wheelchair Sports Quick Straps) were affixed for securing the user’s waist and feet within the KRuW. The KRuW prototypes were equipped with 25-inch wheelchair wheels with ½ inch (12 mm) quick-release axles. Future designs will include the more common 5/8-inch axles. Removeable closed cell foam inserts could be added in the footrest cavity to allow for some adjustment in the footrest height. Fully assembled KRuW prototypes, with seat widths of 14-inch (36 cm, left), 16-inch (41 cm, middle), and 18-inch (46 cm, right).
Once fully assembled, each of the three KRuW prototypes were weighed using a hanging force scale. The 14-inch (36 cm), 16-inch (41 cm), and 18-inch (46 cm) chairs were found to weigh 40 lbs (18.1 kg), 41 lbs (18.6 kg), and 42 lbs (19 kg), respectively. To ensure that the rugby chairs would hold the weight of a user and meet current market specifications, a prototype was statically loaded with 300 lb (136 kg) via a 220 lb (100 kg) person + 80 lb (36 kg) of steel weights. No structural deformation or failure was detected upon visual inspection.
Methods
Focus group evaluation methods
Interview questions asked to participants after performing drills in KRuW.
Results
Participant characteristics/demographics which were collected from participants through a questionnaire.
Focus group evaluation results
The results of the interview questions are presented below, organized by design criteria, with (x) indicating the number of respondents per theme.
Criteria 1: Affordable to manufacture
Participants cited the projected cost (4) as one of the primary benefits. Participants evaluated the KRuW favorably as a beginner rugby chair due to its projected low cost (8).
Criteria 2: Customizable
Many participants appreciated the KRuW’s adjustability (5), particularly regarding positioning of the backrest.
Criteria 3: Allow the user to secure themselves to the chair
Most participants reported that the straps were comparable to a standard rugby wheelchair in terms of placement (9) and ease of strapping into place at both the waist (10) and feet (8). Some participants (3) preferred that the foot straps and sleeve around the strap to be longer for ease of use and comfort.
Criteria 4: Safe transfers
A majority of participants reported that transfers to/from the KRuW was easy (7) or, at the very least, no more challenging than transferring to a typical rugby wheelchair (3).
Criteria 5: Lightweight
Many participants reported that the KRuW felt lighter than their rugby wheelchair (7).
Criteria 6: Maneuverability
Participants provided mostly positive reviews of the KRuW during pushing forward (6) and backward (7) and when performing turns (7) and spins (7), noting that its performance was comparable to or better than their rugby wheelchair. Some participants, however, felt unstable (3), during straight passes and when turning/spinning.
Criteria 7: Compliant with wheelchair rugby rules
Two participants noted that the KRuW prototype does not abide by wheelchair rugby specification standards, pointing to the lack of spoke guards, front bumper height/placement, and rigid back handle shape/material. Participants also inquired about the legality (2) of the KRuW in competitive play.
Criteria 8: Versatility
Participants evaluated the KRuW favorably as a beginner rugby chair due to its projected cost and/or adjustability (8). Some participants, however, called for a defensive-style KRuW, noting that the current prototypes do not offer enough trunk support for low-point players (5).
Criteria 9: Supports the weight of the user
The KRuW prototypes supported the participants under conditions involving dynamic loading, and none of the participants reported any structural failure during or after the drills.
Criteria 10: Durability
Participants wondered about the durability of the KRuW in the context of competition (6).
Additional interview results that were not directly related to the design criteria are outlined below.
Drills
Experiences with ball management differed between participants. Some noted that catching a pass (6) and picking the ball up from the ground (4) felt similar to with their wheelchair. Others found the tasks difficult due to feelings of instability when reaching for the ball (4) and the lack of typical rugby wheels (7) and grip (3) to aid in picking the ball up from the ground.
Positive feedback
Participants cited the overall design (5) as a benefit. Though not explicitly mentioned by the researchers, participants (2) noted that the sheet metal and bolts design may allow for repairability of individual pieces of the KRuW.
Suggestions for improvement
The most identified areas for improvement related to the seat and backrest: dump (5), height (6), design (2). Additionally, some participants disliked the casters (3).
Noise
Most participants did not find the sound of the KRuW particularly noticeable (8). Two participants mentioned that the KRuW is louder than a typical rugby wheelchair but added that the sound should not be an issue.
Seat pan
When asked about their thoughts on the solid seat pan, many participants reported not noticing that the seat was solid (6) but most agreed that an upholstered seat option may be preferable (8).
Rugby wheelchair acquisition
Most participants reported having their rugby wheelchairs purchased, at no cost to them, through Veterans Affairs (9). Nearly every participant (10) mentioned that their non-Veteran teammates experience challenges with acquiring rugby wheelchairs and often rely on inheriting used wheelchairs from teammates or grant funding to purchase a new wheelchair.
Discussion
All three KRuW prototypes were used by participants at the NVWG to complete standard drills. Participants were able to safely transfer into the KRuW that most closely matched their hip width. The prototypes supported each participant’s body weight, and the back rest and seatbelt were able to be adjusted based on individual participant needs and preferences. Our findings suggest that the prototypes largely met the design criteria.
Findings from the interview suggest that participants formed a generally positive impression of the KRuW. Adjustability, reparability, and reduced cost of the KRuW potentially leading to enhanced use and access emerged as a key theme. Because adjustability, especially in the backrest, is rarely found in conventional rugby wheelchairs, this was noted as a potential benefit, particularly when a single wheelchair is shared among multiple users, such as teammates, with varying positioning needs. Similarly, the participants identified cost and time to delivery as a barrier for participation in wheelchair rugby. These findings are consistent with previous research identifying rugby wheelchair cost and time to delivery as a barrier to participation in wheelchair rugby. 33 Consequently, the participants supported the concept of a KRuW with a comparably lower projected cost.
Of note, many users mentioned the KRuW felt lighter their own rugby wheelchairs. Although there was little difference in weight between wheelchairs, the rear wheel axle location and overall accurate alignment of the KRuW frame may have positively influenced center of mass, rolling resistance, and stability, thereby improving propulsion biomechanics.16,17,30,34 It is difficult to maintain precise alignment with a welded frame and fabricators often use shims and other techniques in attempt to align frames after welding. The relationship between rolling resistance and users’ perception of wheelchair weight has been previously noted which may have contributed to participants perceiving the KRuW as lighter during on-court propulsion.31,35
Another important theme emerged when comparing the preferences of offensive and defensive players. All participants who expressed concerns about instability were defensive players, who identified seat dump and backrest height as areas for improvement. Because defensive players typically have greater limitations in trunk function 29 and rely on the chair for stability, they may have been more likely to perceive the KRuW prototypes, which were designed as offensive models, as unstable. From this, they expressed expectations for the development of a defensive model of the KRuW.
The KRuW may necessitate rule changes for wheelchair rugby. However, this is not a new challenge as unanticipated innovations in adaptive sports equipment have previously required rule changes that enhanced the inclusion, safety, and performance of such sports as wheelchair tennis and wheelchair racing.36–41
The demographics of the participants recruited for this study do not necessarily reflect the target audience for the KRuW (i.e. novice rugby players), but those who fall outside the target audience offered insight into the needs of that population. The study participants have a wide spectrum of exposure to wheelchair rugby, ranging from one to 37 years. Thus, the interview questions elicited feedback from experienced athletes who are knowledgeable about the sport as well as novice wheelchair rugby players who more closely align with the target audience for the KRuW. Though most of the participants have standard rugby wheelchairs that were purchased at no cost to them through the VA, all but one reports playing on teams or in leagues with non-veterans and novices who have struggled to obtain a rugby wheelchair and may benefit from the KRuW.
Challenges/limitations
It is crucial to acknowledge that the design had limitations. Due to IRB protocol and lack of bench testing, participants were not allowed to impact other rugby wheelchairs and, thus, were unable to evaluate how the KRuW endure contact. Because contact is integral to rugby competition, this protocol limits ecological validity. Similarly, the KRuW prototypes were equipped with standard wheels with aluminum push rims rather than rugby wheels with coated push rims and spoke guards, which support maneuverability and ball handling. The evaluation portion of this study also has limitations related to small sample size, homogeneous sample, and prototypes being better suited for some players than others (e.g. chair dimensions, exclusively offensive-style chairs). Additionally, though the KRuW is intended to make rugby wheelchairs more affordable, a full cost-benefit analysis has not yet been conducted.
Broader application
While this research focused specifically on the application of kirigami design to wheelchair rugby, the approach has broader potential to reduce the manufacturing costs of many adaptive sports and recreation devices. Progress has already been made in applying kirigami design to build prototypes of a tennis wheelchair, cross-country/Nordic sit ski, and an everyday wheelchair, as shown in Figure 7. Kirigami-inspired design applied to other adaptive equipment, including cross-country/Nordic sit ski (left), tennis wheelchair (middle), and an everyday wheelchair (right).
In the future, the kirigami-inspired design approach could open the door to making affordable wheelchairs for everyday, sports, and recreation more widely available globally. Sheet metal wheelchair parts could be laser cut, flat-packed for efficient shipping, and then bent and assembled locally in areas that do not have access to advanced manufacturing technology such as laser cutters or robotic welders.
Next steps/future directions
Future designs should ensure that the KRuW is compliant with rugby wheelchair specifications (design criteria 7) and has both offensive and defensive variations (design criteria 8). Future assessments of performance should include quantitative measures of performance outcomes and safety and durability outcomes with contact (design criteria 10), along with data collection from a more diverse participant population that includes women and non-veterans. Additionally, a manufacturing cost analysis should be performed to quantify the cost savings of fabricating a rugby wheelchair using sheet metal versus welded tubes (design criteria 1).
Conclusion
The high cost and personalized nature of sport wheelchairs currently serve as barriers to adapted sport participation among PwD. This study aimed to design and fabricate a cost-effective and easy-to-manufacture kirigami-inspired rugby wheelchair prototype and evaluate it through user testing. The resulting prototypes were usable for simple drills and participants were able to provide feedback about features that are favorable and/or need improvement. Interview findings will inform additional iterations of the prototype. Though further development and testing will be necessary prior to commercializing KRuWs, these wheelchairs may lower the burden of entry and, therefore, increase access to adapted sports.
Footnotes
Acknowledgements
Garrett Grindle and Benjamin Gebrosky – Helped with design feedback and troubleshooting. Robert Powell and Jackson Williams – Machined and welded parts for the wheelchairs. Jackson Rozelle and Broc Pearsall – Assisted with fabrication and assembly of the wheelchairs. Nikitha Deepak and Rosemarie Cooper – Contributed to participant recruitment, IRB submission and approval, and facilitated data collection.
Ethical considerations
This project was approved by the Institutional Review Boards of the University of Illinois Urbana-Champaign and University of Pittsburgh (#IRB24-1468).
Consent to participate
Written informed consent was obtained by each participant for each university/institution involved in this study.
Author contributions
Jessica Steinberg
• Designed, fabricated, and assembled rugby wheelchair prototypes.
• Planned and conducted user testing of prototypes with participants at the 2025 National Veterans Wheelchair Games.
• Wrote the Design section of the manuscript and assisted with editing other sections.
Kaitlyn Thornton
• Planned and conducted user testing of prototypes with participants at the 2025 National Veterans Wheelchair Games.
• Transcribed and coded participant interviews.
• Wrote the methods, results, and conclusion sections and contributed to writing the introduction and discussion sections of the manuscript. Assisted with editing the manuscript.
Yukina Ota
• Planned and conducted user testing of prototypes with participants at the 2025 National Veterans Wheelchair Games.
• Coded participant interviews.
• Contributed to writing the introduction and discussion sections of the manuscript. Assisted with editing the manuscript.
Ian Rice
• Kirigami design member
• Grant author
• IRB author
• Supervised protocol development
• Supervised manuscript development and editing
Rory Cooper
• Kirigami design member
• Grant author
• IRB author
• Supervised protocol development
• Supervised manuscript development and editing
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The project was funded in part through the National Institute for Disability, Independent Living and Rehabilitation Research (NIDILRR) Rehabilitation Engineering Research Center (REGE23000233), the Paralyzed Veterans of America, and the U.S. Department of Veterans Affairs (1IK6RX003916-01).
Declaration of conflicting interests
The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
There is no data suitable for public use.