Brooks Glycerin Flex Review: Natural Movement In a Max Package

Introduction to the Brooks Glycerin Flex

THOMAS: Brooks has been flirting with foot articulation for more than a decade. Influenced by the barefoot movement of the early 2000s, the brand set out to create shoes that felt more natural at a time when one of its top sellers was the Beast. That blocky, behemoth stability shoe muted all ground feel and looked like it came straight from a podiatrist’s prescription pad.

In fall 2011, Brooks launched the Pure line, introducing lower drops, lighter weights, and a push toward a more “natural” running form. When the Pure line eventually faded, Brooks continued experimenting through one-off projects like the Neuro and the Aurora-BL. The Aurora-BL, in particular, became one of our team’s all-time favorites.

Brooks Aurora-BL

The Glycerin Flex builds on years of trial and error and proposes a novel solution to the following challenge: runners now expect lightweight shoes with abundant cushioning—so how do you deliver all that comfort while still maintaining a dynamic, engaging underfoot feel? To Brooks’ credit, they’ve pulled it off here, introducing a genuinely new sensation to the max-cushion category.

MEG: I stopped by Brooks HQ this past summer and got a sneak peek at some upcoming releases – one of them being the Glycerin Flex. It was described to me as a max-cushion shoe with more ground feel, which honestly sounded like the opposite of what I want. I love max-cushion shoes precisely because I don’t want to feel the ground.

The good news? That description didn’t quite match the reality.

So what exactly is this new trainer from Brooks? The shoe has deep roots within the brand and is essentially the result of more than a decade of evolution. It comes from Brooks’ “Blue Line,” their innovation-focused pipeline designed for faster experimentation and development. If that name rings a bell, the Blue Line previously gave us shoes like the Aurora-BL (a true throwback for the shoe nerds) and one of our recent favorites, the Glycerin Max.

The Glycerin Flex uses the same DNA Tuned midsole foam found in the Glycerin Max, but with strategic cutouts throughout the midsole that create a noticeably unique and flexible underfoot feel. Up top, the shoe features an engineered flat-knit upper with a stretchy pull tab and tongue for easy entry and comfort. The outsole is finished with a thin layer of rubber.

So is Brooks’ innovation team onto something here, or does this feel like a step in a strange direction? Let’s get into it.

What we like about the Brooks Glycerin Flex

THOMAS: The knit upper on the Glycerin Flex is surprisingly elegant. Not only did it accommodate both my narrow foot and Meg’s wider one, it stretches where you want it to and holds structure where it matters. The knit also hides some thoughtful details: a subtle Brooks logo woven into the medial side and a dual-layer construction that reveals flashes of color as the shoe moves through the stride.

The colorway I tested featured a white upper with highlighter-green accents, a look that’s mirrored in the dual-density foam below. Extra padding around the heel counter delivers a gentle, secure hug at the ankle, while a wide, thin tongue rounds out a comfortable and dialed-in fit. Simply put, the attention to detail in this upper is impressive.

The midsole, however, is the true star of the Flex story. Built from a dual-density supercritical foam familiar to anyone who’s tried the Glycerin Max, it delivers plenty of cushion with a noticeably more dynamic feel. Thanks to a decoupled heel and deep forefoot grooves, the midsole feels like it breathes and expands with each footstrike. While most max-cushion shoes rely on a pronounced rocker to move a slab of foam through the gait cycle, the Flex feels more like independent suspension for different parts of the foot. Some might even call it more natural.

Rounding things out is a sticky, dependable outsole. My men’s size 10.5 weighs in at 10 oz (285 g). The shoe fits true to size, though if you’re between sizes, I’d recommend going down a half size.

MEG: I usually give Brooks a hard time for their aesthetics, but I have to admit, the Glycerin Flex looks really good. My white/cyber pink colorway is especially nice and the accents are subtle without feeling boring. 

The step-in feel is equally lovely. The knit upper hugs the foot comfortably, and the stretchy pull tab and tongue make it easy to slip on while delivering a secure, comfortable fit. It’s not especially wide or voluminous in the forefoot, but the shoes stretch nicely to accommodate just about any foot shape. 

The DNA Tuned midsole is where this shoe really shines. The foam has a dynamic, responsive feel, and the strategic cutouts combined with asymmetrical flex grooves create a truly unique ride. It delivers the protection of a max-cushion shoe but with noticeably more control. I felt especially confident running down steep hills.

What we don’t like about the Brooks Glycerin Flex

THOMAS: There isn’t a lot to dislike. I would like to see the tongue to be integrated into the upper as you see with the Mizuno Neo Vista. 

MEG: I did notice some rubbing under the ball of my big toe (worth noting that I also have very cute bunions), which I suspect is due to my foot moving more than it’s accustomed to. It wasn’t a dealbreaker or a major knock on the shoe, but it did make me a bit hesitant to take it out for runs much longer than eight miles or so.

Final thoughts on the Brooks Glycerin Flex

THOMAS: Brooks isn’t a brand you typically look to for bold, experimental takes on running shoes. Part of its DNA is a simple philosophy: don’t surprise the consumer. That approach has worked. There are plenty of runners who just want the identical dependable shoe, year after year, in a new colorway—and Brooks delivers precisely that.

That’s why a shoe like the Glycerin Flex is so exciting. The Flex feels genuinely new from top to bottom. The development team took on a real design challenge and arrived at a solution that actually works. Hopefully, unlike some past experiments, this isn’t a one-and-done model. Hopefully they don’t tweak it to much in the next version and destroy a good thing they had going (looking at you, Glycerin Max 3).

I enjoy the sensation of the Flex, and its lighter weight compared to the Glycerin Max makes it a more versatile option in a training rotation. It’s a reminder that when Brooks decides to push beyond its comfort zone, good things can happen. Let them cook.

MEG: I never quite know what to expect from Brooks, but the Glycerin Flex was a genuinely pleasant surprise. What stands out most is how wide its appeal is. Runners who love a high-stack ride (i.e. me) will feel right at home, but those who prefer a lower, more traditional feel will likely enjoy it just as much.

The ride feels more natural, transitions are smoother, and your foot is free to move the way it wants to move. It delivers cushioning without feeling bulky and encourages a rhythm that feels easy, fluid, and unforced. Overall, this feels like a thoughtful and fun step forward for Brooks, and it’s refreshing to see the brand lean into innovation.

You can pick up the Brooks Glycerin Flex for $170 on February 1 from brooks (featuring free shipping and 90-day returns) by using the buttons below.