CastleFlexx is a multi-purpose stretching and strength tool designed to help athletes, fitness enthusiasts, or anyone with chronic pain improve both their flexibility, core strength and mobility. CastleFlexx targets the entire posterior chain of the lower limb by stretching the soft tissues of your toes, foot, calf and hamstrings. It creates a fascial and nerve tissue release that improves issues related to lower back pain and herniated discs, and can even cure plantar fasciitis. Castleflexx was created around the desire to make "Prehab" easy and accessible, to help people prevent injuries before they happen.

CastleFlexx was born from founder Dan Castle's desire to improve his own lower back pain. He developed a prototype with a biomechanical engineer, and then approached Leadoff Studio to take the prototype to the next level. We worked closely with Dan to consider all users, from professional athletes to elderly physical therapy patients. In the early stages of discussing the project, Castleflexx and Leadoff connected on a mutual desire to create sustainable products. Considering this wide demographic and focus on eco-friendly materials, we knew we could design a product that would deliver a comfortable and accessible prehab device.

After many months of research, development and testing, we produced a dynamic device made from innovative materials in the workout space. The CastleFlexx starts with an ergonomic aluminum bar capped with natural cork handles on each end. A single piece of non-stretch fabric connects to the bar, unfurling to reveal a "foot hammock" where users place their heel. Laying on their back or sitting in a chair, users grip the handles and fully flex their toes backwards, resulting in a flexed plantar fascia. We also designed a mid-bar cut-out for a 2-pound magnetic weight for increased resistance and specialized mobility workouts.

We focused on user interaction during use, travel and storage. Every detail is intentional, many doubling in functionality. For example, the aluminum pull tab at the bottom of the foot hammock secures the fabric when rolled-up and can be used as a handle to assist with fitting on the heel. The CastleFlexx is made using three materials: infinitely recyclable aluminum, sustainably harvested cork and RPET fabric made from 100% recycled plastic bottles. The entire device is antimicrobial and designed to last a lifetime.

We designed CastleFlexx to be universal enough for anyone to use, while maintaining a level of quality fit for professional athletes to stretch with. The Atlanta Braves used CastleFlexx in their 2021 World Series championship season to increase speed and mobility. The device has been quickly adopted by physical therapists, chiropractors, and trainers to help treat or train their clients. Individuals suffering from arthritis have ditched their stretch bands for the CastleFlexx, opting for comfortable handles and reduced stress on the hands and wrists. CastleFlexx is a truly accessible and effective device: a lightweight, tactile experience designed for anyone to use.

From Prototype to Prosumer Device

Long before we transformed a homemade prototype into the CastleFlexx, Dan Castle had tried everything to relieve his lower back pain. Physical therapy, massage, chiropractors and pilates helped, but he was struggling to get to the root cause. Thanks to a chance encounter at a pilates studio, he collaborated with a biomechanical engineer specializing in human body movement to create the first CastleFlexx prototype.

He approached Leadoff Studio with an unconventional apparatus made from PVC pipe, plastic grips and neon green nylon fabric with a hole at the bottom. Yet for something stitched together on a sewing machine in the garage, it was remarkably effective. It stretched the entire posterior chain of the lower limb while extending the toes in dorsiflexion, effectively curing plantar fasciitis. Dan had found the core functionality of CastleFlexx. It was time to design a "prosumer" level version with thoughtful materials and details, suitable for mass production.

We focused our design research on defining an eco-friendly material palette, nailing all of the user touch points, and elevating the CastleFlexx to a multi-functional device. The prototype version stretched the entire leg, relieving lower back pain and very effectively treating plantar fasciitis. The mechanism was stress-free and easy to use, making it ideal for all ages and abilities. We set about modifying the design with design details that enhanced the overall user experience.

Design Development

An idea we had as an early sketch was to mill out a section of the center of the bar that could add different functionality. The notch that we created became a flat landing for customization for larger enterprise sales to gyms or teams. The negative space taken out of the cylinder became a spot we'd use to allow users to slightly increase the weight. With this weighted option, the device could enter the active stretching and prehab fitness categories, emerging approaches to exercise that researchers say reduce injury and increase power and flexibility.

We used a combination of prototyping methods to test out the weight, combining 3D prints with plastic and metal rods, and panels of muslin fabric. Through prototyping we found that the weight could snap into the notch using magnets, and wrap around using velcro for added security.

Our prototyping with soft goods led us to a more efficient fabric design as well. The initial prototype from the biomechanical engineer used a strip of webbing to wrap around the back of the heel. We ended up creating a single piece design, in which the fabric panel stretches down into the heel hammock. Through many rounds of prototyping, we determined the ends of the fabric needed to overlap and terminate at a specific diagonal angle to avoid rubbing against the achilles during stretch. We designed the heel hammock so it could flip inside out in either direction and still be usable.

Sustainable Materials

On the end design we replaced the original prototype's PVC pipe with sandblasted aluminum. One of the most commonly used metals in the world, its lightweight and rigid properties lend itself to many applications across diverse industries. It's also one of the most recycled materials on the planet because its properties never deteriorate during recycling: Almost 75% of all aluminum ever produced is still in use today. With the highest strength to weight ratio compared to all other metals, it was the ideal material. Aluminum is cost-effective, and we were able to save additional money using aluminum extrusion during production.

The CastleFlexx handles are made using 100% cork. Naturally antimicrobial, anti-bacterial and water-resistant, cork has an inviting texture and warm feel. The use of cork became CastleFlexx's way to signal its sustainable credibility, and the warm aesthetic of the material lends itself to the relaxed feeling users look to achieve during prehab. Cork stands out starkly from the rest of the exercise industry that relies heavily on petroleum based elastomers for grips and handles. CastleFlexx cork is sustainably harvested and naturally biodegradable.

The canvas-like panel is made from recycled PET fabric, reclaimed post-consumer plastic spun into a sturdy, lightweight polyester. Absolutely no virgin plastic was used to make the CastleFlexx.

In addition to eco-friendly materials, sustainable printing practices and end-of-life recyclability were major factors in our design strategy. Rather than relying on toxic inks, we laser-etched the aluminum bar and embroidered the canvas with the CastleFlexx wordmark. Both techniques result in premium, long-lasting results, and they don't produce the environmental waste associated with dyeing and printing. CastleFlexx is constructed to last for decades, but if users do need to recycle the product, they can send it back to the manufacturer for disassembly and recycling.

Changing the Game

Throughout the design process, we continually returned to the target users, a wide-ranging group of individuals with diverse needs. People with arthritic hands as well as people over the age of 65 provided valuable insights. CastleFlexx replaces stretch bands, towels and ropes because not only are they not as effective, but they also put unnecessary stress on hands and joints. It can also be used in seated positions and while laying down. It's lightweight yet durable, built for daily active stretching and training. These features culminate in a universally accessible device, equally effective for all users.

CastleFlexx fills a gap in the strength and mobility prosumer category. By optimizing one simple movement, the device provides professional-grade rehabilitation that was only previously available in a medical setting. Inclusive design, sustainable materials and high-quality craftsmanship make for a satisfying experience, one that users seek out to improve their daily lives.

Design Details

With a focus on user interaction, the details account for every scenario, including use, travel and storage. When users unwrap the device, they can use either side, as both embroidered with the brand logo and a centerline to help with foot placement. The double-stitched canvas has a notch in the middle that allows users to hold the center of the bar with one hand and pull back for an even deeper stretch.

An aluminum pull-tab adjacent to the foot hammock doubles as an alignment tool, helping users who have injuries, arthritis or other mobility issues reach to get the loop around their heel. When it's time to roll it up for storage, users can go in either direction and secure the pull-tab on the toggle loops located on both sides.

Aesthetic

CastleFlexx is designed to fit seamlessly into an active lifestyle, while promoting the calming "prehab" mindset. The natural aesthetic, premium materials, and pastel color palette look good in any room, yoga studio or chiropractic office. When rolled up, the slim profile makes it easy to pack for traveling. We designed the 2-pound detachable weight to fill the notch and perfectly complete the cylinder of the bar, allowing users to quickly increase or decrease the intensity of their workouts without having to deal with bulky attachments. The weight is magnetic, but we reinforced it with a velcro strap as an added safety measure. The weighted bar keeps the upper body balanced so that users can maintain a deep fascia stretch.

Now available to the general public, CastleFlexx is quickly becoming a sought-after tool in the self-care and rehabilitation product category. Users can benefit from the simple, accessible design while stretching at home or on-the-go. Sports therapists, chiropractors and yoga & pilates instructors incorporate CastleFlexx into their regular practices. Even professional athletes across many sports—from golf and tennis to baseball and basketball—use the device to improve flexibility, increase power and reduce injury rates.

Ergonomic, sustainable and exceptionally effective, CastleFlexx provides a multi-functional experience that allows everyone to comfortably achieve their mobility goals.