In this episode of the Functional Tennis Podcast, I’m joined by Yuhi Tanigaki, Product Manager for Tennis Footwear at ASICS, to go behind the scenes of the new Solution Speed FF4.

Yuhi plays a central role in shaping ASICS tennis shoes, working closely with designers, researchers, professional athletes, and recreational players to turn feedback into real on court performance.

We cover what actually goes into building a modern tennis shoe and how small changes can make a big difference.

In this episode, we discuss:

1. How long it really takes to develop a tennis shoe from first idea to retail
2. What stayed consistent from the original Solution Speed and what has evolved
3. The key updates in the Solution Speed FF4 and how they affect feel and movement
4. How ASICS balances speed, comfort, and durability without adding weight
5. The role of athlete feedback, including insights from Belinda Bencic
6. Differences between what professional players and recreational players value
7. Why ASICS sees the FF4 as an evolution rather than a complete redesign
8. Which type of player the Solution Speed FF4 is built for

This episode is a deep dive into tennis footwear design and a rare look at how performance products are actually created behind the scenes.

Welcome to the Functional Tennis Podcast.

I'm your host, Fabio Molli and I bring you insights and lessons from players, coaches, parents and experts who are ingrained in the world of high level tennis.

Today's episode is a little different and one I've been really looking forward to.

I'm joined by Yuhi Tanagaki, product manager for tennis footwear at Asics and the man behind the development of the new Solutionspeed FF4.

If you've listened to this podcast for any length of time, you'll know the solutionspeed has been my go to shoe for years.

So this conversation goes deep into how the FF4 was developed, how long these shoes really take to make, and how much athlete feedback actually shapes the final product and whether the latest version is an evolution or something more.

We also talk about what recreational players really care about versus pros, and how Asics balances speed, comfort and durability in a modern tennis shoe.

This is the proper behind the scenes look at how a top level tennis shoe comes to life.

Let's get into it.

Yuhee, welcome to the Functional Tennis podcast.

Nice to meet you again.

How are you?

Nice to meet you, Fabio.

I am doing good.

This is my favorite shoe.

I've harped on it about on the podcast every most weeks.

Back then it was.

I still remember it, I still remember the green colored version and it's always been the right characteristics for me.

So I love promoting it if you're looking for that sort of shoe and so always excited when there's a new version out and I tried it yesterday so I'll give you my feedback on it.

But first of all, you are, you are product manager at Asics for Tennis.

What does that mean?

What, what's your, what's your day job?

My role is really about connecting players, the market and our internal teams, so and turning all those insights into a clear direction for all the shoes that we create.

So on a daily basis I'm looking at how these players move, what they struggle with and what gives them confidence on court.

Then I translate that into a product strategy and then build briefs, work with our designers, developers and researchers, reviewing prototypes and making sure that every update has a real purpose behind it.

The gel.

And you're the jail in all this.

Everything comes through you or you're firing off missiles everywhere.

Yeah, I guess I helped shape the tennis shoes that you see on court today.

And so how many pro players, professionals would you work with at one time?

Regarding this year, I know Belinda was played a part in this shoe, but would there be like 10 players you work with?

How many?

Oh, there's a lot.

Are you getting feedback from many players?

Like just getting many players.

And what about amateurs?

Amateurs, of course.

We play test with amateurs within Japan, within Europe, within the States, everywhere.

And we gather all those feedbacks, those insights, and I tried to make it into a brief to make those shoes even better.

Wow.

And yeah, it's a great job to have where you're connected to so many different people.

I was always, I was always into a light shoe.

And when I heard Asics releasing that shoe, I was really excited.

Now, I used to wear Asics a long time before that as well.

But in the meantime between before that, I tried different shoes.

I remember it was green and it was just great from day one and you could wear it straight away.

It wasn't a stiff shoe.

But for you, since that shoe, what stayed consistent since day one within this line and what's changed over the years?

First of all, thank you.

It means a lot to hear that you've worn pretty much every version of the solutions speed, and not only the solution speeds, but all our models.

And you know, this franchise has been around for more than a decade, so having someone like you follow it that closely is really special for us.

It's always been our lighter, faster tennis shoe.

So quick through transitions and perfect for those players who like to use the whole of the tennis court.

And that core DNA hasn't changed, but what has changed is how we deliver that speed.

So with the early gel solution speed models, we used a more traditional cushioning setup with the gel.

So the era with flight foam, which modernized the cushioning and introduced at the same time, we introduced the twist truss system for more controlled stability.

And as the game evolved, the twist truss became the speedrust in the solution speed FF3 to support the explosive movements that the players use today.

The personality of the shoe has remained pretty consistent, I would say, but the tools and the technologies behind it have continued to evolve to keep up with today's tennis.

And actually, that evolution is a big part of what shaped the new FF4, but I guess we'll go into that in a second.

Yeah, I have a question later on whether it's a evolution or revolution.

So I'm going to have to go into the ASICS archives next time there's an event and sometimes you bring the old shoes.

That could be really interesting.

But how long did it take from day one where you went, okay, it's time to work on the FF4 to actual it's available in the shops.

How long is that process?

Development process, or shall I say the design process and to the shelves it takes normally about one and a half year to two years.

How much of that time is spent on Cortes?

And I know in the past sometimes like the sole of shoes would be the exact same, you know, from model to model.

They may not put, I know in the FF3 you got this.

There was the AI, I think it was the soul was developed by AI, I think.

And now I see FF4, there's a completely new pattern underneath.

And I, I gather that takes more time to test.

So how much time is actually spent on core tests and refining the soul pattern?

Because it is different to, you know, what you think of historically.

So throughout those one and a half to two years of the whole process, each stage, each sample stages, we test a bunch of wear testing shoes with our professional athletes, with our amateur athletes, with everyone.

And sometimes it's more than 100 when you want to try something new, you know.

But yeah, there is, it's always dozens of wear testing shoes.

One is to make sure that the shoe performs as we intend it to be or as we want it to be.

And then the other thing is about the durability because it has to perform, but at the same time it has to stay durable.

Yeah, we get to durability because that's always a key consumer, you know, that's, they always want durability, durability and I notice a compromise between softness and playability.

And you're trying to get that mix right.

But as somebody, now I did this yesterday, but as somebody who comes from an FF3 shoe into an FF4 shoe, what should be the biggest thing they feel immediately when they put them on?

Oh, that's a good question.

But I think if you're coming from the FF3, I think there are three things that you'll notice right away when you step into the FF4.

So the first Thing you'll feel is the cushioning.

We adjusted the flywheel midsole density so that the FF4 feels more cushioned and a bit more lively underfoot, but still very lightweight.

And it's more of a comfortable ride without losing the speed first identity that the solution speedfans love.

And the second thing you'll notice is the quicker acceleration.

So the updated speed truss gives you more support when you're pushing off, especially moving forward, so you get that instant, confident go feeling, so it feels more stable but not heavier or restrictive.

And then the third one is the traction on the outsole on the forefoot.

So the new precision sole with Asics grip in the toe area gives you more bite when you're changing directions and when you're dashing towards the net.

Okay, Interesting.

Well, I'll tell you what I noticed, which is I did feel.

I'm just.

Yeah, I felt they were more comfortable without a weight compromise.

It feels great.

It feels like.

It nearly feels like a bigger shoe, but lighter, if that makes any sense.

I expected to be heavier than what it was.

If it's hard to explain.

You got to put it on and I just felt, oh, it feels more comfortable and lighter than I expected.

It feels.

That was interesting.

Obviously, I think the shoe, you can always wear it right away.

Like, I had it on straight away and you can push off.

It's not a stiff shoe, so it's quite.

It doesn't take.

I know there's other shoes where it takes the cord.

FF takes a lot longer to wear in than this shoe, so that's really good.

I found it a tiny bit wider.

Just a tiny bit wider.

Just random.

But I find the size and a tiny.

These are only a millimeter.

Tiny bit shorter, though.

Ran.

Oh, that's interesting.

That was just what I found now.

But in.

In general, you know, it's not like a new shoe.

It feel.

Obviously it is.

I said it feels more comfortable and it feels light.

But the feed adjusts to it quickly.

There's no, like, the arch doesn't change much or, you know, it doesn't give you any feed issues.

So for me, going from FF3 to 4, it was good.

There was only one trial.

It'll take me a few times.

But yeah, initial thoughts is, I like it crazy.

Great job.

It's light, which is important.

And obviously I think what you've done well with the solution suite over the years is make it a light but comfortable shoe.

You can wear it all day if you want.

So good job.

Now, if I come from Another shoe.

Whether it's another ASIC shoe or another shoe brand, what are the things that somebody will feel immediately when they put on this shoe?

It's kind of similar to my last question, but different.

I'm recommending people this solution speed and they're coming from another shoe.

What do you want them to feel when they put it on?

It's of course about the speed, but it always has been about that balance.

So comfort without losing speed.

So when we worked on the solution speed FF4, that was the number one thing that we didn't want to compromise.

So the big change is how we approached comfort.

Instead of adding more foam or more material, which would make this shoe a bit heavier, slower maybe, we focused on making the existing system work smarter.

So we adjusted the flight foam midsole density so it gives you more cushion and a livelier feel.

And with the updated speed truss, we designed it in a way to give more support with geometry, but keeping the same weight as it's known for.

So all these things without adding any extra weight, we're trying to achieve this cushioned, lightweight speed.

So I think the balance between comfort and speed, this is the number one thing with the Solutionspeed FF4 that I would love people to try it on.

And is that the feedback you get from amateur players and pro players, they like that mix of comfort and speed?

Yes.

Especially around that cushion.

They notice it almost immediately when they try it on.

Not even on a tennis court.

You just try it on and then you stand up, you immediately feel that cushion.

So, yeah, it is one of the most noticeable features or the feedbacks that we got from the pro players and the recreational players throughout the whole process.

And so flight foam on the tree and flight foam on the four.

Is it?

It's a more improved fly foam.

Is it?

Oh, yes.

So the call out, it's still the same flight foam, but we adjusted the density slightly so that it gives you more cushion and actually more rebound.

So that gives you more of a lively feel, a more feeling, that propulsion or.

Yeah, like a reactive underfoot feeling.

Interesting.

And this, the speed trust, where you know, this first step you've made quicker.

How do you actually test that?

How do you make something quicker?

Like we're talking milliseconds here, I think.

And it's feel as well.

So it's two things, it's actually quicker, but two, it's how it makes you feel and how do you actually gauge that?

It's a lot of research, it's a lot of gathering insights, feedbacks from not Even the existing models, but all over the.

From basically everywhere that we can find that hint, find that insight.

So, yeah, with the solution speed FF3, it was already a fast shoe, but we wanted to improve even more.

So the forward, that forward acceleration and the first step are huge for us, especially in a shoe.

Like the solutionspeeds that build for aggressive moves or aggressive movers.

And honestly, like I said, a lot more research goes into that movement than people might expect.

So we look at players footage, motion capturing, pressure mapping, basically trying to understand what happens in those first two or three steps when a player explodes forward.

And that's where so many points are won or lost in today's tennis.

Right.

So the FF4, the biggest change came from what we learned about the forward push off.

We updated the speed TR geometry so it gives you a stronger support when you load your foot and drive forward.

So it's engineered to guide and stabilize that initial flex of the forefoot and then release you into that quicker toe off.

There's a lot going on.

Lot going on.

Yeah.

No, so a lot of work goes into.

But I'm.

I'm even thinking now even like stuff like socks can make a difference as well.

You know, if you have a poor pair of socks on, they're slipping your foot.

Well, that will make you.

So, you know, like even wearing the right socks is important as well to give you that extra bit.

I.

So you worked with Belinda on this shoe heavily?

Yes, sir.

Belinda Bench, who the Olympic champion and who's playing great tennis at the minute.

Like, what were the biggest feedback you got from her that were incorporated into the shoe?

So working with athletes like Belinda is of course for us it's incredibly valuable because they notice these tiny little sensations in his shoe that most players would probably never think of.

Right.

And sometimes their feedbacks come from very real on court situations at the absolutely top level.

So there's an interesting story that the.

Belinda told us about a moment where she was reaching for a bowl, she smashed her foot really hard onto the court and she felt that impact linger for a couple of days.

This was from way back, but we were talking about the shoe and how we can improve this.

And she was talking about this incident that happened years ago.

But that experience made her sort of emphasize how important cushioning is for protecting the foot during those sudden aggressive movements.

So those kind of feedback is really important to us, especially when it aligns with what we're seeing in biomechanics testing and with other players, not only Belinda.

So it's not always about Personal preferences, but it's more about real performance needs.

And so cushioning and underfoot feel became a major focus for the Solutionspeed FF4 project.

So we, like I said, we tune the flight foam density to get more cushioning with, you know, paired with the new updated speed truss to keep stability and acceleration sharp.

But at the same time, yeah, we don't really build a global shoe around one person's exact preference.

So some, some feedbacks are very, is very individual, individual things like specific fit nuances or unique movement habits and we treat that as like a context and not a direction.

So athlete PBAX is really hugely important, but it's always combined with biomechanics research and consumer testing and what we know about the modern game demands.

Is there any one thing that Belinda wanted that you guys were like, no, you're not getting that we just can't do that?

No, I think overall she was really happy with this shoe.

So.

And she was especially happy with the cushioning because we, from the conversation we had previously, we incorporate that into the new shoe.

So yeah, there was nothing specific that she didn't really like, not that I can remember.

When did she, let's say she's top elite athlete.

When did she first trial this shoe?

The moment she first tried the shoe was around last summer I would say because with all the, you know how long the tour is, right?

ATP, WTA Tours is so long.

So we're trying to schedule that very specific window that she can test this shoe.

And we tried to use all the methods that we have and from a very scientific point of view, we tried to test and validate how her movement is working with the new shoe.

And that happened on that last summer.

And can you test, you have certain tests that you can have a player in a shoe and then put player in another shoe and get proper numbers to see, okay, this shoe's actually made you quicker or this or that.

Can you figure that out?

There are ways to do that, but it's not always easy.

Right.

Because when you're used to a one shoe that you've been wearing for almost two years and then you try a fresh pair that is new.

So even if the shoe works, you'll still need to have a bit of time to get used to it.

It's not always the results through the tests that kind of validates the shoe is better or not.

But we have all the professional researchers in our brand, so yeah, they run the test, they analyze it and we together with our athletes, we make it better.

And you may not have the answer to this only thought of it.

Now two questions here.

How long does a pair of shoes last the Linda and how many pairs of shoes does she go through in a year?

Well, it all depends on players and how they move.

I guess if you slide more obviously you wear it out faster.

Even with the pro players.

Some they wear this shoe for two tournaments, some they change it in two, three matches.

It's not because of the durability, but sometimes about the player's preference.

Some people prefer a slightly wore out shoe because it feels that they have more control in it.

And some players, they prefer a fresh pair for matches.

So I can't really say how long but it really depends on how these players want for this shoe and how these players move in those shoes.

And do you have any idea how many pairs of shoes these top professional athletes get a year?

Oof, that's a great question.

It all depends on players but and also we change the colors from time to time.

Maybe like in two, three months for a fresh head to toe look that suits each swing.

But I guess some, yeah, some people wear it more than like 60 pairs and some people stick to 30 pairs.

It all depends on the players, but they go through a lot of shoes.

And okay, we've talked a lot about professional athletes here.

Amateurs.

You mentioned it before how like you know, you think of shoes designed by professional players for amateurs.

You know, it's always like design comes from the top end or input from top end but from actual amateurs.

How much feedback do you actually take from amateurs?

And it is amateurs who wear the bulk of these products.

There's a lot more amateur tennis players than professional tennis players by a great magnitude.

So feedback from amateurs, how important is it for you?

I guess it depends on which shoe we're trying to make.

Right.

And if we're Talking about our Elite 3 models, the solution speed, the resolution and the chord FF for those Elite models I think the pro players feedbacks influence the final decisions a bit more.

But we offer a wide range of tennis shoes.

So if you look at like the challenger the solution swift then it's more about what the recreational players need.

Right.

But yeah, Even with the Elite 3 models, we always play test with recreational players from a lot of levels and we try to incorporate those all those insights into a one truly perfects you that we at least think nice.

And Asics, you know ASICS philosophy is the Kaizen philosophy where it's continuous improvement.

Now the FF3 to FF4 has that been from that principle?

So is it an evolution Or a revolution.

Well, like you said at asics, we always come back to that Kaizen principle, which means continuous improvement in Japanese.

So that's been our philosophy for over 70 years.

We focus on identifying real athlete needs and making step by step improvements.

And with the solution speed FF4, I would say this was more of an evolution.

So the FF3 already worked extremely well for fast attacking players.

So we refined the areas that matter most.

So more cushioning, sharper speed, truss, and a more precise outsole with an added grip.

And when we choose evolution or revolution, it really comes down to understanding trends in tennis and how the players today are moving.

And if I guess the sport demands something totally new, we go big.

But to me, I feel like when the foundation is strong, Kaizen guides us to elevate it.

Okay, and two more questions.

One is, what do recreational players care more about in the shoe rather than professional players?

Can I answer it?

Can I answer my own question?

Yes, Yes, I love to hear it.

Is, is it durability?

Because, you know, I see a lot of comments from recreational players I talk to a lot and it's always like they all, it's durability.

They want value for money, they want shoes to last.

Now, I personally don't have a job with the issues.

I don't think I play enough tennis, I don't think I move enough.

So yeah, for me they will last longer because I'm not, and you know, I'm not sliding on the court.

But would you agree that a professional player may not care about durability, but a recreational will?

Oh, no.

Professional players, they also definitely care about durability, but like you said, I think durability is one of the biggest things that recreational players really want because they pay for that shoe.

And of course they want it to last longer.

Right.

But there are definitely differences.

And one great example is actually the new detail on the Solutionspeed FF4.

It's the hidden laces on the medial side.

So most recreational players, they probably don't destroy their laces very quickly.

But professional players, especially the younger generations, you see them sliding more aggressively on hard courts and they can burn through a pair in no time.

So their media laces are constantly scraping the court during those long control slides.

And if the laces break mid match, the fit is immediately gone.

Right?

So we hit the laces on the medial side to keep them protected and maintaining that secure fit throughout the whole match.

And it's a feature that the professional players really appreciate because of how they move.

But recreational players still benefit from it too, I believe so even if they don't slide as much, I think they get a cleaner look on the shoe, better durability and a consistent lockdown.

So I think that's the beauty of it and solving a problem like a pro level problem in a way that enhances the experience for the recreational players.

Nice.

And final question is if you're at a tennis tournament and you're watching tennis players play, what is the exact player?

If you see a sort of player, it's like they should be wearing FF4s solution speed.

FF4s what in your eyes, I know we mentioned earlier is a player that would benefit from an FF4 solution suite.

FF4, their character, the player characteristics.

So we design our tennis shoes based on our playing style, principle or philosophy and for the solutionspeed we designed it for the all court players and if they were to try the new shoes, I don't know.

I think the players that are looking for two things at the same time, lightness and confidence.

And the lightness in the sense that the shoe almost disappears on your foot.

Because I always tell this to my team, that confidence on your foot or confidence with the shoe equals peace of mind and that equals to peak performance.

So I always tell this to my team and I think the Solutionspeed FF4 has the best balance of it.

It feels flexible cushion and it's ready to move with you.

And that confidence thanks to that updated speed trust, the secure fit with the hidden laces and the precision sole with the Asics grip and everything.

So if you're a player that can step out and take a couple of early balls, let's say and change directions quickly, I think they will immediately think that okay, this feels quick and controlled then I think we've done our job.

And that first feeling of freedom of your movement, that's the the new solution speed is all about.

So I hope yeah, we're designed the shoe for those type of players.

Yui, that's great.

Thank you very much.

It was great learning about the new solution speed and I look forward to wearing it throughout the year.

Thank you.

It.