The running shoe landscape feels like a bit of a playground right now. Brands are doubling down on their proven staples while also experimenting with bold new ideas—sometimes subtle, sometimes anything but.
Brooks enters that conversation with the Glycerin Flex, a shoe they’re calling a world-first in flexible cushioning. It was one of the standout talking points at TRE, and after getting time in it, we can see why. This isn’t just a Glycerin tweak—it’s a fresh take on how softness and flexibility can work together underfoot.
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Looks:
The Glycerin Flex looks refreshingly clean up top. It remains to be seen how many colorways will ultimately be available, but the initial launch keeps things simple with a crisp white upper, accented by subtle neon underlay hits that add just enough pop without overpowering the look. It’s a classy, good-looking running shoe.
There look to be 3 other color options as well – all of which are pretty muted and classically fresh.
At first glance, the upper itself looks fairly familiar for a Brooks. Flip the shoe over, though, and that’s where things get interesting. The outer midsole and outsole designs immediately stand out, giving the shoe a futuristic edge that contrasts with the otherwise classic aesthetic. It’s the kind of detail that might actually stop someone mid-run to ask what you’re wearing.
Construction:
The Glycerin Flex really lives up to its name—it’s built to move with your foot. Instead of a standard midsole, Brooks has added sculpted flex points that help the shoe bend more naturally, all while keeping the soft, cushioned feel Glycerin shoes are known for.
The idea is simple: instead of your foot having to adjust to the shoe, the shoe adjusts to your foot. Special grooves in the midfoot let the shoe bend from the middle of your foot to your toes, so it moves more like your foot does, not against it.
The result is a smoother, more natural stride. Running in the Glycerin Flex feels less stiff, more fluid—like the shoe is helping your foot roll through each step rather than fighting it.
Specs:
- Stack height: 36mm (heel) / 30mm (forefoot)
- Drop: 6mm
- Weight: 9.1 oz (men’s 9)
Fit & Feel:
After years of running in shoes with predictable cushioning and flex, I thought something new like this would take a minute to get used to. Runners who prefer a slightly lower drop and a more flexible forefoot will likely notice the difference right away, and honestly, most runners will feel it in some way.
Honestly, after talking with others in the running community who were “in the know,” I expected a much bigger shift in feel. That expectation is actually part of why these sat on my shelf longer than they should have—I was worried the ride might be too much.
But at least for me, the change wasn’t monumental. There were noticeable differences, as expected, but nothing that completely rewired my brain. It was a more grounded feel than max stack shoes out there. That’s not to say it was firm and rigid – quite the contrary. It was just more in tune with the ground than those high stacked shoes where you can hardly feel the ground at all. Some may love this – others may not.
I’d recommend easing into them—every foot responds differently—and, if possible, trying them on in-store or giving them a few runs before making a final call.
However, the feel may not be as dramatic as you’re anticipating (it wasn’t for me), so don’t write them off even if they feel a little different at first. Give them some time, and the shoe starts to reveal what it’s really capable of.
Upper:
Flexibility isn’t just in the midsole—the upper gets in on it too. Compared with Brooks’ other cushioned shoes, the Glycerin Flex has a noticeably more flexible upper. Even the internal heel counter bends a bit, but the padding and overall comfort remain excellent.
I was initially a little worried that all this “flex” talk might come at the cost of a secure fit, but the shoe locks down nicely. There’s just enough give so your foot doesn’t feel boxed in, yet it doesn’t compromise stability. It’s a really nice hold and comfy upper.
Midsole:
Underfoot, the Glycerin Flex isn’t completely reinventing the wheel. It still uses Brooks’ DNA TUNED nitrogen-infused midsole, the same technology found in shoes like the Glycerin 22 (one of my favorite trainers from last year) and the Glycerin Max 2. The design combines larger nitrogen pockets in the heel for plush landings with smaller pockets in the forefoot for a snappy, propulsive toe-off.
As mentioned above, I haven’t felt the new components added in really changed the ride. It feels like that Glycerin 22 midsole I love so much – with perhaps a tiny bit more flex (obviously). It’s a really nice and fun ride.
Outsole:
There’s not a ton to say here, but that’s a good thing. Despite the flexible midsole and split outsole with separated areas, it still provides solid grip. Thick layers of rubber offers confident traction, even on slick pavement during my first run (Oregon running in the winter probz), and it looks like it’s built to hold up for many miles.
Overall:
I genuinely wish I hadn’t waited so long to pull these out of the closet. The Glycerin Flex is a solid daily trainer that manages to balance comfort and innovation better than I expected. It’s worth checking out to see how your feet respond, but I wouldn’t write these off at first glance—you might be missing out.
An added bonus: despite the flex-focused design and narrower look, there’s a surprising amount of stability here. Since I’m firmly in my cross-training era, I’ve used these for post-run strength sessions and found they performed better than most running shoes when it came to lifting. I never felt off-kilter or unstable.
Whether it’s the flex geometry or the platform itself, this ends up being a more versatile, multi-functional shoe than it appears on paper.
