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TENTIAL's 'Recovery Sandal Pro': A New Design Born From the Foot Data of 400,000 Japanese People, Engineered for Walkability
TENTIAL, known for its popular recovery wear 'BAKUNE,' has launched the 'Recovery Sandal Pro,' a new product engineered using foot data from 400,000 people in Japan. This new sandal moves beyond the conventional focus on softness to pioneer a new standard of 'walkability.' We sat down with Shunji Moriya from TENTIAL Inc.'s Product Division and Kentaro Yahata from the Conditioning Research Institute's R&D Evidence Group to discuss everything from the product's development backstory and the unique characteristics of Japanese feet to the current landscape of the recovery sandal market.
PROFILE
Shunji Moriya
Product Planning & Development Group, Product Division, TENTIAL Inc.
Moriya joined TENTIAL in 2022. Drawing on his 13 years of experience in competitive tennis, he is involved in planning and developing high-performance recovery sandals tailored to the feet of Japanese people.
PROFILE
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Kentaro Yahata
R&D Evidence Group, Conditioning Research Institute, TENTIAL Inc. After graduating from the Department of Health Sciences at Hokkaido University's School of Medicine, Yahata earned his master's degree in Rehabilitation Science from the same university. He joined TENTIAL in 2023 after working for companies like Mizuno Corporation. He is involved in the R&D of high-performance recovery sandals, leveraging his expertise from both the medical and shoe development fields.
The recovery market has seen continuous growth in recent years. TENTIAL launched its first recovery sandal back in the summer of 2021.
"Back then, the prevailing idea was that as long as a sandal was thick and soft, it was good enough," Moriya explains. "Of course, we conducted thorough R&D before launching our product, but we couldn't shake the question, 'Is softness alone really enough?' That's why we decided to completely rethink the design."
Rethinking the Effectiveness of Popular Recovery Sandals
TENTIAL's flagship product is their 'BAKUNE' recovery wear. The concept behind it involves embedding minerals into the fabric to boost blood circulation and promote fatigue recovery. The team wondered if this same principle could be applied to sandals."That turned out to be a major flop," Moriya admits. "It was difficult to embed minerals into the sandal material, so we experimented with inserting magnets into the sole, hoping to achieve a similar blood-circulation-boosting effect. But no matter how many times we tested it, we couldn't produce any clear, advantageous results. After about a year of refinements and testing, we made the call to scrap that approach and go back to the drawing board."
Guided by their principle of "never releasing a product without solid evidence," the development team pivoted in a completely new direction.
"Once we determined that incorporating the blood circulation angle was too challenging, we went back to a fundamental question: 'What truly makes a sandal good for the body?'"
Today, the market is flooded with countless recovery sandals, yet there is no single, unified definition of what a 'recovery sandal' actually is.
"We came to the conclusion that it's just not realistic to expect full recovery simply by wearing a pair of sandals. So, we thought, 'What if the starting point for a recovery sandal was to ease the fatigue you feel after a long walk or a workout?'" (Hachiman)
"Like I mentioned, most recovery sandals on the market focus on a soft feel to cushion the impact when your foot lands. The problem is, if they're *only* soft, you can feel wobbly when you walk, which makes you use extra muscle power just to stay stable.
Ever had that annoying experience where your sandals are flapping around, or you have to clench your toes just to keep them from flying off? That just makes your muscles work overtime and leads to more fatigue. That's what led us to focus on three key elements: 'softness,' 'stability,' and a 'snug fit' that makes walking a breeze." (Moriya)
What Foot Data from 400,000 People Revealed About Japanese Feet
That's where the foot data from 400,000 Japanese people came in handy. The development team dove into this massive dataset, identified six typical foot shapes, and then narrowed it down to a single, 'average' model based on six key measurements, including foot width, arch height, and heel position. This model became the foundation for our design."We started our design from the heel's position. This revealed that the arch is set slightly further back compared to existing models. There's also this common belief that Japanese people have wide feet—many even opt for 3E or 4E wide-fit shoes. But surprisingly, our data showed the opposite: the average foot width is actually narrower, around 1E to 2E. The catch is that the arch in Japanese feet is quite flexible and tends to spread out under pressure. This is what causes toes to rub against the shoe and create pain, leading many to believe they have wide feet."
To address these unique traits of the Japanese foot, we positioned the arch support closer to the heel and designed it to be higher, preventing the arch from spreading out under weight. We also enhanced the fit with a heel-hugging shape.
One of the biggest development hurdles was achieving a "softness" you could really feel the moment you put the sandals on.
"It’s crucial that people feel that softness intuitively when they slip the sandals on. But there's a limit to how soft you can go, especially with quality assurance constraints. That’s why we opted for a dual-layer structure with both a soft and a firm material," (Hachiman)
The Dual-Layer Sole: Balancing Softness and Stability
The sole features a soft upper layer that cradles the foot and a firm lower layer for support. We also designed the outsole with a bowl-like shape, making the soft material thicker in the center."When you step down, the center sinks in nicely, giving you that plush, soft feeling. At the same time, the firm material on the outer edges provides solid support, keeping your heel stable and preventing any wobble," (Moriya)
We also gave the sandal a slight toe spring (a raised toe) and a flat heel. This design helps prevent tripping and ensures a stable landing with every step, making for a much smoother walk.
Even better, motion analysis from a research institute confirmed the design's advantages: it puts less strain on the body, reduces ankle wobbling while walking, and softens the impact load on landing.
It's not just about chasing softness; it's about designing for stability with every step. That’s TENTIAL's new vision for what a recovery sandal can be.
"Conventional recovery sandals were typically seen as something you’d wear for short trips or just around the house. But with this product, you can comfortably walk a kilometer or two without any issues," (Moriya)
At the same time, both of them agree that there are still challenges ahead.
"To properly hug the heel and leverage the three-dimensional arch shape, we had to create a design that securely wrapped around the foot's perimeter. This made the sandal's silhouette a bit bulkier and added some weight.
You don't really notice it much when you're wearing them, but looking ahead, we want to tackle the challenge of making them lighter," says Hachiman. Moriya adds, "And I believe there’s still plenty of room to improve the cushioning, stability, and fit.
We're not just going to rest on our laurels with the current product; we want to keep pursuing new research and fresh approaches."
The new recovery sandal, packed with innovative features, has been a runaway success. Sales were so strong that an additional production run was ordered just one month after launch, creating an unprecedented buzz within TENTIAL.
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"While our primary focus is e-commerce, when it comes to shoes, many customers still prefer to visit our physical stores to try them on. In fact, our store staff are reporting low stock levels. The Net Promoter Score (NPS), a key metric for customer loyalty, is also trending higher than our company average, which tells us that the sandals are being very well-received," Moriya explains.
Looking ahead, the company is exploring autumn/winter models, indoor slippers, and even different material variations. It seems the options for supporting foot conditioning are set to expand beyond just sandals, covering everything from life at home to your time on the go.
"Awareness of recovery sandals is definitely on the rise. At the same time, we feel it's crucial to clearly communicate their specific benefits for the body and the unique features they offer.
Our goal is to establish our value in the market by prioritizing evidence-based development. We hope that our products can offer some support and aid recovery for people who are constantly on the move. This philosophy is the common thread that runs through all our products," says Yahata.
Through its data-driven design, TENTIAL has introduced a new benchmark for recovery sandals: "walkability." With their stated mission to "improve the physical condition of people in Japan," one can only wonder what kind of footwear experience they will create next. The evolution of recovery sandals is just getting started.
Text by Junko Hayashida
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