Improving Circulatory Health
TS Medical approached Priority Designs with an idea and a rough prototype of a resistance-training device that would allow users to exercise in a way that mimics the act of walking, all from the comfort and stability of a chair. The target market for this product are individuals who have an immediate need to improve their circulation, such as sedentary seniors and those working long hours at a desk or traveling.
While TS Medical had a prototype of the device, the design was not suitable for travel and had not been developed with mass production in mind.
TS Medical approached us with several tasks, including:
- Reformat the device into a solution convenient for travel.
- Create an attractive and user-friendly design.
- Ensure manufacturability.
After 4 years of development, FitFoot™ was launched in February 2023!
History Behind the Idea
TS Medical is committed to supporting better health for all with innovative and simple exercise devices for home, travel, and clinical use. FitFoot™, their first product, aims to promote blood flow, lymph drainage, and strength building. It may serve tens of millions living with chronic conditions such as peripheral arterial disease, chronic venous insufficiency, and diabetes. It can also provide support to millions more dealing with the effects of
COVID-19 or living a sedentary lifestyle. Additionally, it’s popular with physical therapists, who see the potential to support rehabilitation after injury or surgery and even prehabilitation before surgery.
Founder and CEO, Mary Anne Tarkington, MD began this journey when she recognized a need for products that improve circulation and reduce the risk of blood clots. Being a surgeon, she is particularly sensitive to the serious nature of blood clots, which are a well-known complication of surgery and certain chronic diseases. Today, she leads the company’s research program, focusing on circulation-boosting tools to prevent such complications.
To learn more about TS Medical’s products, as well as key scientific and medical research,
please visit www.tsmedical-llc.com.
Design Exploration
Priority Designs began the design effort by sketching in CAD and quickly prototyping initial ideas, using foam and wood to test various form factors to determine which pedal format provided the most stable platform for exercises to activate the body’s circulatory system from the lower leg.
Following several rounds of prototyping, we identified the optimal pedal design for this application: a top rectangular plate featuring an A-frame structure support beneath, connected by resistance bands.
Material Exploration
The next step in development was to determine whether the product should be crafted from wood or plastic. Both material options had their pros and cons:
Wood
PROS: More affordable and gets TS Medical to production sooner, as it eliminates the need for tooling.
CONS: Individual parts are more expensive and potentially harder to clean.
Plastic
PROS: Provides a broad spectrum of color, finish, and shape options, and it makes the product feel high-quality and robust.
CONS: Increases time to production and up-front costs.
Initial prototypes were created with 3D printed fused deposition modeling polylactic acid (FDM PLA), known for its relatively rigid composition and durability.
TS Medical showcased the completed PLA prototype at a trade show to attain early feedback from consumers. During the event, a user placed it on the floor and unexpectedly stood on it, causing the prototype to crack. Regardless of the product’s intended use, users were inevitably going to stand on it, so we needed to explore a stronger material for the manufactured device.
The next iteration was made from HP fusion 3D printed nylon; a significantly more robust material compared to PLA. However, part of nylon’s strength comes from its flexible nature, so prototypes made of this material were described as flimsy and didn’t convey much strength or comfort under a user’s foot.
After evaluating various materials, we opted for glass-filled nylon. While nylon alone is more flexible than desired, the addition of short glass fibers renders it exceptionally rigid, boasting an 80% increase in strength compared to its unaltered form.
Engineering Resistance
Deciding on the best material for the resistance bands was a separate project itself. We needed to find a solution with the appropriate amount of stretch but could also provide the resistance needed for the device to be clinically effective.
Option 1: Bungee Cords
Bungee cords were an obvious choice due to their combination of stretch and resistance. Bungee cords have a fabric outer coating and a rubber core, making them a durable option. However, testing revealed that a bungee cord will only stretch 100% beyond its original length and the fabric would fray over time as it stretches around the internal structure of the device.
Option 2: Latex Bands
We considered surgical tubing and rubber bands, as they can stretch 2 ½ times the length of the original unstretched band. However, the risk of latex related allergies could limit the consumer audience.
Option 3: Silicone Bands
We discovered a silicone band that came in vibrant colors and could stretch up to 1000% of its original length, which appeared to be an ideal solution. However, upon consultation with the client’s clinical specialist, it was determined the bands lacked the necessary resistance for the intended use.
Following a series of tests with the silicone bands using our Mark 10, a machine to simultaneously measure displacement and force, we determined the bands with 6lbs of resistance best met the market requirements. We accomplished the desired 6lbs of resistance by increasing the silicone’s durometer. If necessary, we had the option to further raise the band’s durometer to achieve a maximum resistance of 9lbs to increase intensity.
The silicone bands were loaded onto a custom-made test fixture on the Mark 10. This test fixture used the cyclical motion of a motor to stretch the band repeatedly to simulate the device in use. After up to four days of monitoring, we observed that the bands only lasted 28,000 cycles before breaking, falling short of the intended target of 120,000 cycles.
Silicone wouldn’t achieve the cycle goal at that strength and durometer, so we needed to take a different approach and move to medical-grade TPE (Thermoplastic Elastomer). TPE proved to be the perfect solution providing us with a longer life cycle at a reduced cost. After landing on TPE, there were still quite a few iterations required to overcome design-introduced obstacles and to ensure the material could withstand the required number of cycles.
Later iterations included a custom grommet within the loop of the band to prevent wear from the posts on the pedal. The grommets significantly increased the lifecycle of each band.
Engineering Refinement
We performed crush tests using an Instrom machine, where we discovered the glass filled nylon prototypes can withstand up to 1,200lbs of pressure before failing.
Fine Tuning Details
After finalizing the material composition, details were thoughtfully integrated to finalize the product design.
Blue bands were the color of choice to align with
TS Medical branding.
Grip tape was used for an anti-slip surface.
Additional labeling was added to make it clear the product is not intended to stand on.
FitFoot™ was manufactured in the United States.
Final Design
The FitFoot™ pedal is durable, capable of enduring hours of exercise, yet remains lightweight and conveniently portable for travel. The system was thoughtfully designed for individuals with diverse dexterity levels, marking another significant step towards improving leg circulation.
We’re pleased to announce that FitFoot™ has been featured as one of the top 50 most innovative products for 2023 by Innovation & Tech Today!
“Priority Designs was an ideal partner for an inventor entrepreneur with no engineering background. I knew what I was trying to achieve, they helped me articulate that vision and make it a reality. The engineers were patient, answering all of my questions, and explained the thought process in terms I could understand. I never felt rushed or as though I was being pushed in a particular direction.”
