Review: Gliding in the Glycerin 21, Brooks’s Smoothest Shoe Ever

The latest trainer from the Washington-based running company promises a cushy ride, but how does it actually stand up?

March 5, 2024 11:28 am
a Brooks trainer on a blue spring backgrounds
Brooks' latest train is the running companies smoothest ride yet.
Brooks/Getty Images

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What do runners really want out of their trainers? PR-breaking super shoes or a 50mm stack height might seem like the obvious choice, but the answer I hear most commonly from everyday runners isn’t concerned with lightning-fast speed or cloud-level cushioning — it’s centered around injury prevention. More than ever, sensible sneakers that keep you healthy and on your feet are in demand, and Washington-based Brooks might have just cracked the code.

Review: The Ghost Max Introduces Peak Cushioning to Brooks’ Stacked Lineup
We tested the new maximalist trainer. Here’s what we thought.

You probably recognize Brooks as the maker of the cult (and currently on sale) Ghost silo, but the running company’s strides in both performance — Josh Kerr, Brooks’ top middle-distance athlete, just won gold at World Champs in dominant fashion — and everyday training are no joke. We gave the new Ghost Max a rave review, a testament to the massive network of wear-testers and oodles of tech crammed into Brooks products.

With the launch of the Glycerin 21, the latest from their stability line, Brooks is looking to strike gold with another excellent everyday trainer, this time gear towards a smooth and cushioned ride. Featuring a reworked upper and Brooks’ latest DNA LOFT v3 cushioning, the Glycerin 21 has been branded as Brooks’ softest sneaker yet, perfect for those easy runs that should make up the bulk of your training.

Given their recent run of form (and the fact that I am already something of a Brooks-angelist), I decided to test out the cushy trainer for myself, After a month-ish of training, here’s my proper Brooks Glycerin 21 review. More on that below.

Brooks Glycerin 21, at a glance


  • Midsole Drop: 10mm
  • Weight: 9.8 oz.
  • Type: Road
  • Support: Nuetral
  • Widths: 1D-2E
  • Sizes: 7-15
  • Colorways: 8
  • Best for: Easy Runs, Recovery Runs

How we tested

Over the course of nearly a month, I’ve run 60-odd miles in the shoe for this Brooks Glycerin 21 review, predominantly on easy or recovery runs. These range from runs through my local Prospect Park to time on the track. I did not try to run on rough terrain — the Glycerin 21 is firmly a road shoe, and I was immediately wary that I might injure myself trying.

What we liked

  • Improved cushioning: There’s no way around it — the appeal of the Glycerin 21 lies in its cushioning. Adding an additional 2mm of Brooks’ proprietary DNA LOFT foam, the Glycerin 21 gets the update treatment with the latest version (v3) of the aforementioned nitrogen-infused cushioning, a marked improvement on even the plush Ghost Max.

    Like the Max, the foam’s ability to maintain structure upon impact — in practice, this means that the foot remains in control and cushioned, rather than sinking into the midsole — sets it apart from nearly anything else on the market, but I found the roll of the Glycerin to transition much better through the stride, with the outsole shape more conducive to smooth transitions (not unlike the On Cloudmonster) despite a similar amount of foam. Easy runs have never felt smoother.
Brooks Glyercin 21
Glyercin 21 offers Brooks’ smoothest ride yet.
  • Stable ride: In conjunction with the new foam, the oversized base of the Glycerin 21 and classic fit proves a super secure fit. I’m never worried about rolling an ankle or slipping, and at sensible paces, the heel-to-toe transition moves like butter. As you get up to speed, the shoe begins to feel clunkier, but for easy and recovery runs, it’s basically an anti-injury trainer.
  • Reworked upper: A change in upper is as likely to go poorly as it is to revolutionize a trainer (I still distinctly remember the terrible transition Nike Pegasus went through a few years back), but the Glycerin 21’s update seems to be worth the squeeze. The new engineered warp knit upper is both breathable and moves well with the foot, and despite being a bit snug (we’ll get to that), feels comfortable when putting in the hard miles.

What we didn’t

  • Heel cushioning: My biggest complaint about the Brooks Glycerin 21 is with the mass amount of heel cushioning. Normally, I’m all for a bit of added protection riding up into the Achilles, but I found the combo of plush cushioning and stiff heel counter excessive, and, at times, counterproductive to delivering that ultra-comfortable ride that I was looking for. Not a deal breaker, as it rarely impacted my stride, but it was absolutely noticeable for a sensory freak like myself.
Brooks Glycerin 21
Brooks Glycerin is stacked on top of a massive amount of foam.
  • Sizing issues: The other potential issue revealed itself in the actual logistics of the shoe — as a true size 10, the updated upper on the Glycerin 21 has a slightly smaller than average toebox, especially when compared to other Brooks styles, and proved a touch too snug for my liking, forcing me to size up by a half. I didn’t have too many issues with the jump, but there was a noticeable gap between my toe and the front of the shoe, a turnoff for some runners. snug shoe fans, beware.

The verdict: should you buy the Brooks Glycerin 21?

As far as I’m concerned, anyone looking for a calculated combination of ride and cushion will thrive in Brooks’ latest addition to the Glycerin line-up. As I’ve mentioned, it’s not a particularly speedy shoe, and the cushion stack can feel offputting for minimalist runners when compared to classic styles like the Ghost, but overall, the Brooks Glycerin 21 breathability and transition proves a marked improvement for the everyday trainer silo.

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