Grey and Yellow Gel-Nimbus 21 running shoes sitting on the ground


Go behind the scenes of the GEL-NIMBUS™ 21 shoe with Jork Geraets, product line manager of global footwear. Here, he shares his insights on the design, development and inspiration of our best neutral running shoe yet.

How do you approach the idea of improving upon the GEL-NIMBUS shoe over time? What is your goal, and how do you pursue it?

The GEL-NIMBUS shoe is, and needs to be, the most luxurious neutral-cushioning shoe on the market. It needs to have the perfect blend of cushioning, comfort, stability and durability. The runner can use the shoe for all distances, but the combination of these four factors makes it perfect for long distances. I’ve personally used many GEL-NIMBUS iterations for my marathon trainings!

To make the GEL-NIMBUS™ shoe the best it can be, we continuously monitor how runners are reviewing the model. We do this through our wear-testing programs, following reviews and conducting focus groups with runners. We also work with our Institute of Sport Science in Kobe, Japan to come up with material and construction innovation.

What felt like the biggest challenge, or the biggest breakthrough, with the GEL-NIMBUS 21 model?

We pride ourselves in making a consistent and reliable product for consumers. We follow the Japanese method of kaizen, which means the pursuit of continuous improvement. We’re always trying to be better, in every detail. This is what has led to the popularity of the GEL-NIMBUS shoe and why it’s been around for 21 iterations!

The biggest challenge in designing the GEL-NIMBUS 21 model was improving the fit. To get it how wanted, we went back to the drawing board and developed a new last (the mold the shoe is based on) to fix that problem.

Our biggest breakthrough was in the inclusion of our new FLYTEFOAM™ Propel technology, which is an advancement of FLYTEFOAM™ technology. This new midsole material has great bounce and a nice plush underfoot feel.

The new design and materials presented a challenge when it came to production—the first sample didn’t come out as we hoped. So, we made revisions to get it where we wanted it. It was a lot of work and we were making changes late in the process, but we did what we had to to get it just right.

Close up of the Gel-Nimbus 21 Shoe.

How do you take runner feedback and learning into account as you design new models?

We have several ways that we gather feedback. First, we look at the reviews from runners and take their shoes back to study the wear. While in development, we work with an independent wear-test agency to test every round of samples. This lets us see how the shoes hold up after many miles of running and in different types of conditions. Then, we can address any weaknesses or flaws in the materials or design.

And of course, at ASICS headquarters, we have a lot of runners who help us by giving their feedback. We also do focus groups with runners and store associates.

How did you test the new design of the GEL-NIMBUS 21 model?

It’s very important that our team—designer, design director and product line managers—all feel comfortable with the shoe. We also get feedback from our regional merchandise teams in Europe, the United States, Japan, Australia and China. On top of that, we visit some of the leading run-specialty stores in the U.S. to get their input as well.

How do you know when you’ve got it right?

Basically, you know when you run on it and feel the underfoot sensation and fit. And of course, we check the wear-test results as well. If it feels right, and it does well in the wear tests, it’s a successful design.

What type of runner is the GEL-NIMBUS 21 shoe good for?

The GEL-NIMBUS 21 shoe is great for all distances, because the comfort and protection it offers is perfect for both the beginner as well as the serious runner who wants to go farther. This model has good stability, but if you are an overpronator, you might want to try the GEL-KAYANO™ 25 shoe instead.

What’s the experience of running in this shoe like? What is it designed to do?

The name of the shoe comes from nimbus clouds. We want runners to experience the feeling of running on cloud-like softness.

Woman running down road, wearing Gel-Nimbus 21 running shoes.

To you, what’s the most exciting thing about the GEL-NIMBUS 21 model?

The fit has improved a lot, which is essential for success. The feeling of running on the new FLYTEFOAM Propel technology is also super nice. We think fans of the GEL-NIMBUS series will appreciate this update!

What are the technical details of this shoe?

One of the first things you’ll notice is plenty of room in the forefoot for your toes, so that it’s comfortable and not restrictive over long distances. The new jacquard mesh upper is breathable and flexible, but gives your foot support where needed. Underfoot, you have GEL™ technology and FLYTEFOAM™ Propel technology to absorb shock and give you a bounce-back feeling. We also redesigned the outsole so that it’s one piece instead of two, which makes every step feel more stable.

How might you describe the “personality” of this shoe?

I think of it like a best friend that you can rely on.