Over one million Americans rely on their upper extremities for manual wheelchair propulsion. Shoulder overuse injuries are prevalent among manual wheelchair users and these injuries often result in shoulder pain. Severe shoulder pain can lead some wheelchair users to transition from manual to powered mobility, complicating transportation, and reducing independence in activities of daily living. This project will expand the understanding of a new wheelchair design that allows better positioning of the hand rims and allows for different gearing. The investigators will study steady-state propulsion efficiency with different gear ratios and develop a new system with multiple gear ratios. The advanced gearing will allow for a low gear when initiating movement, going uphill, or when moving over carpet, and then a higher gear option for movements on hard flat level terrain. This system has the potential to dramatically improve shoulder ergonomics and reduce pain in many future manual wheelchair users.

The Minneapolis Adaptive Design & Engineering (MADE) Program has recently developed ergonomic wheelchairs that use a chain drive system to place the hand rims in an ergonomic position while keeping the rear drive wheels posterior for a stable base of support. The investigators' ergonomic wheelchair's forward hand rim positioning allows for a more efficient push along a longer arc length of the hand rims, without sacrificing wheelchair stability or shoulder ergonomics.

The ergonomic wheelchair's chain drive allows for individualized gear ratios to suit each wheelchair user's needs; however, the investigators have not yet studied this feature. Thus, the objectives of this proposed work are to (1) explore the effect of different gearing options on Veteran wheelchair user steady-state propulsion efficiency, and (2) develop a multi-speed ergonomic wheelchair allowing for lower gears during difficult situations (initiating movements, moving over carpeting) and higher gears for steady-state movements on flat surfaces.

The investigators will recruit 18 Veterans with SCI/D to participate in a cross-over study of the ergonomic wheelchair with three gear ratios (3:2 (low), 1:1 (normal), and 2:3 (high)). The investigators will use two measurement approaches to assess efficiency: (1) work done at the pushrim hubs to move the wheelchair in Joules (J), and (2) the measurement of energy (kCal: kilocalories) expended by the Veteran to move the wheelchair. Similar to miles per gallon in a car, the investigators will calculate distances traveled in meters (m) per energy units (m/J and m/kCal) as the measures of efficiency. The investigators hypothesize that (H1) Higher gear ratios will be more efficient (higher m/J) on hard level terrain than lower gear ratios, (H2) Lower gear ratios will be more efficient (higher m/J) for inclined terrain than higher gear ratios, (H3) Lower gear ratios will be more efficient (higher m/J) for carpeted terrain than higher gear ratios, and (H4) Veterans will be more efficient (higher m/kCal) in moving the wheelchair during the 6MPT on hard level terrain when using higher gear ratios compared with lower gear ratios. In addition to steady-state measures, the investigators will also explore the effects of gearing on propulsion initiation and expect lower gear ratios will be beneficial for initiation on all terrains.

The investigators will then recruit 12 Veterans to try a new multi-speed ergonomic wheelchair that has two hand rims per side - one in a lower gear and the other in a higher gear. The proposed system does not require manual or electric shifting between gears. Instead, the Veteran can use the lower gear to initiate movements and then "shift on the fly" by simply pushing on the other hand rim. Veterans will return to the laboratory and provide feedback as the design is iteratively improved. Quantitative and qualitative data will be captured to determine feasibility of this approach and to promote commercialization of the multi-speed ergonomic wheelchair.

Throughout the project, the team will work closely with VA's Technology Transfer Program and the TechLink Center to find an industry partner for this work. The investigators' team has demonstrated the ability to develop rehabilitation products into commercially licensed products. The investigators will follow a similar stage-gate process in this development project to maximize the chances for successful commercialization of the modular multi-speed ergonomic wheelchair.

Inclusion Criteria:

Inclusion criteria:

• Uses manual wheelchair daily
• Mass less than 125 kg
• Age 18 or older
• Decisional competency to provide consent and cognitive ability to participate fully in study procedures
• Body size appropriate to fit the wheelchairs (16" and 18" seat widths)

Exclusion Criteria:

Exclusion criteria:

• Sitting surface pressure injuries
• Flap procedure to address pressure injury less than one year earlier
• Unable to obtain clinically acceptable seating system for study wheelchairs
• Not able to propel a manual wheelchair
• Upper extremity or spine issues which would make this study unsafe, such as recent surgeries, fractures, tendon tears or nerve impingement (will be assessed by SCI physician - Dr. Byron Eddy)
• Medical conditions such as cardiovascular disease, pulmonary disease, or other conditions that would make the study procedures unsafe (will be assessed by SCI physician - Dr. Byron Eddy)