Running on compliant surfaces is safe but challenging, and controlled challenges can build up strength in healthy athletes and foster recovery during the rehabilitation process for injured athletes. The principal investigator (PI), Dr. Jafari, seeks to understand the role that surface stiffness plays in walking gaits, metabolic costs, and muscle activation demand, both for healthy individuals and for mobility-impaired patients. In order to analyze the effect of surface stiffness systematically, the PI needed an apparatus whose surface compliance level can be accurately adjusted. Drawing from his previous experiences in designing and developing Variable Stiffness Actuators (VSAs), the PI envisioned a novel dual-belt treadmill whose surface compliance could be mechanically adjusted using a compliant lever mechanism. Using this mechanism, the surface stiffness can be continually adjusted so that it can range from completely rigid, making it function like a typical commercial treadmill, to completely passive, with a theoretical stiffness of 0. The PI developed a prototype of the Treadmill with Adjustable Stiffness (TwAS) with a team of students working on a senior design project. The PI then attached to the treadmill a partial-weight-bearing harness system called LiteGait, which was meant both to ensure safety and to facilitate rehabilitation. Using this system, the gait of the user can be recorded with an eight-camera Vicon motion-capture system and the metabolic cost can be measured with a VO2-max system. Muscle activation can also be estimated with electromyography (EMG) electrodes. Some initial tests were conducted on healthy individuals, and the results were published in several journals and presented at various conferences. 

The PI and his team attended one of the 80 nationwide NSF I-Corps Nodes, which was hosted at The University of Texas at San Antonio (UTSA). After the team completed the program and interviewed 25 potential customers in the San Antonio area, the NSF instructor recommended the team for inclusion in the national NSF I-Corps 2018 Fall Atlanta Cohort and awarded it a $50K grant for customer discovery (Award# 1850898, title: I-CORPS: A Treadmill with Adjustable Stiffness with integrated measurement systems for rehabilitation applications). The I-Corps project?s intellectual merits include its novel method for designing and fabricating a treadmill whose walking surface flexibility can be adjusted. The user can bilaterally adjust the treadmill?s surface stiffness in a purely vertical direction, regardless of the relative location of the user with respect to the treadmill. The stiffness can be changed very quickly with strong stiffness-adjustment motors and a properly selected short lever. We anticipate that this technology will have a broader impact than other treadmill technologies because it can enhance independent mobility in the mobility-impaired population, which would positively impact quality of life and reduce the economic burden on mobility-impaired persons, their families, their insurance companies, and the government. As of 2015, there were more than 18.2 million mobility-impaired people in the U.S., the majority of whom are post-stroke patients. A stroke occurs in the U.S. every 40 seconds, and the aggregate lifetime cost of first strokes is about $40 billion per year. In addition, nearly 40% of people age 65 and older have a walking disability.

Based on lessons learned during the I-Corps program, the team conducted another 210 interviews with potential customers around the nation and progressively modified the customer segment and value proposition columns of its business canvas. The team initially measured its value propositions in terms of increased speed in the achievement of rehabilitation outcomes with decreased costs, making it a potentially valuable system for physical therapists at after-stroke rehabilitation institutes. The primary advantage of compliant surfaces, which are widely used in rehabilitation institutes, is that they provide more challenging (yet safely controlled) conditions for the patients, which require more muscle activation, leading to faster recovery times. However, somewhere around the 50th interview, the team realized that the ability to adjust surface stiffness might be more beneficial for athletic trainers because it can help them train athletes to reduced the frequency of injuries and improve recovery times during the rehabilitation of injuries. We learned that the type of surface on which an athlete runs affects the quality of performance and that different running surfaces have different effects, and some can decrease the likelihood of injury. That realization became the pivot point in our costumer discovery process. From that point on, our interviews focused on athletic trainers as our target market segment. The results confirmed our hypothesis, that there is a great unmet need for adjustable-surface compliance runways in this field; however, we also found that our technology was not ready for use in athletic rehabilitation centers, primarily because the TwAS was designed for mobility-impaired patients who can walk at a maximum speed of 0.5m/s, not for athletes who can run at much higher speeds. 

Last Modified: 10/29/2019
Modified by: Amir Jafari