Brooks Glycerin 21

• Posted on 18 December 2023
• By Running Lab Staff
• 0

The Glycerin 21 is the update we didn't know we needed. In contrast to the Glycerin 20, the Glycerin 21 presents an additional 2mm more of plush nitrogen-infused DNA LOFT v3 cushioning as well as a newly engineered warp knit upper cradling your foot with the perfect balance of flexibility and support. The Glycerin 21 also comes in a GTS model for added stability and a StealthFit option which is more of a sock like upper. 

THE SPECS

Support: Neutral 

Weight: 9.8 oz (men), 8.8 oz (women)

Midsole Drop: 10mm

Cushion Level: High

ON THE RUN

Blake: I loved running in the Glycerin 21, besides the ice that I encountered on the streets of Michigan, typical for the ever-changing seasons, every step felt fluid and soft. The slightly larger forefoot base gave my foot the needed space to land comfortably and the added flexibility with this new model makes running exciting. I truly felt supported with every step I took in the Glycerin 21 and that’s not something I can say about every shoe. The weight is quite light for the amount of cushioning that the shoe is strapped with and it makes the turnover between every step fast. After spending time running and walking in the shoe I would note that there are advantages to one over the other. As the heel is not super stable this makes walking in the shoe not as comfortable as the experience of running. That being said the experience running is perfect in the Glycerin 21 and the little bit of unsureness I felt while walking is something I can easily gloss over.

THE FIT 

Blake: I found the space in the toebox of the Glycerin 21 to be more spacious and comfortable than the Glycerin 20 and many other shoes. There is also more flexibility in the upper due to the new material compared to the previous model which leads to a slightly more accommodating fit. I have noticed while putting pressure on the big toe that the upper does slightly cave into the foot which also happened to me in the previous model and didn't prevent me from loving that one, so I don't think it will be a big deal here. 

The heel of the Glycerin 21 is comfortable. The shoe grabs the heel and does not allow for any slippage whatsoever. There is a good deal of foam that wraps the heel but it doesn't intrude on the heel or ankle which makes it a standout in its high cushion category. It would not surprise me if this was the same heel counter from the Glycerin 20, as they feel the same.

The length is as consistent as every other Brooks model that is not any of their “speed shoes” (IE: Hyperion Line). Very comparable to Ghost Max, Glycerin 20, Ghost 15, and Adrenaline 23. The Glycerin 21 has a perfect amount of length when you go true to size.

The tongue of the Glycerin 21 carries over the same tongue as the 20 as it stays just as plush and consistent. It does still lean over to the lateral side of the shoe over time walking around, but while running this isn’t a problem. This is something that has never bothered me by the way they have shaped the tongue. As it is padded enough to eliminate the chance of tying your laces too tight.

There is more stretch in the upper in comparison to other Brooks models. I don’t find this to be a negative as I believe this won't stretch out enough to make the fit sloppier over the life cycle of the shoe. There is enough hold that keeps your foot solid in the shoe but with more stretch than before. I would also add that the upper is way more breathable than most Brooks shoes. 

THE FEEL

Blake: The cushion is quite soft, especially in comparison to the previous model. There is still a firm feel with the Glycerin 21, it is softer than the previous model but compared to most other high cushion shoes on the market. It still is relatively firm. I enjoy this factor of the shoe, mostly because it feels like it will last a long time. I feel like some of my other Brooks models have broken down quicker than other shoes so the firmness gives me the confidence this one will last longer. 

I would say the Glycerin 21 is kind of stable. As the forefoot is wide enough you get a stable forefoot, but I wouldn’t say that is the same case for the heel. As it is more semi-curved lasted it does not feel as stable as most neutral shoes on the market. If you are looking for a way more stable base the Glycerin 21 GTS would be the shoe for you. That being said I do find the more flexible feel in this model to be a little bit more responsive. And this makes running in the shoe for comfortable than ever before. Making it a vast improvement in that factor in comparison to the previous model.

THE NITTY GRITTY 

Blake: I would recommend this shoe for most miles. A great everyday shoe as well as a long-run shoe. It’s super responsive yet soft at the same time, making it feel nimble due to its weight. I found the more curved heel makes the shoe feel more flexible. This in return makes the shoe great for all the miles you can run. The only time I found myself not picking up the Glycerin 21 was for speed workouts and races. There are other options that I find more lightweight for that activity. Making the Glycerin 21 the shoe for everything else and in-between.

There are a large number of shoes that the Glycerin 21 that are similar to, but I wouldn't say compare to. Other than the Glycerin 20 which is extremely comparable, the 21 is just the softer upgrade of that shoe. The shoes comparable to the Glycerin 21 would have to be the Saucony Triumph 21, Diadora Vortice, and Topo Phantom 3, all for different reasons. The Triumph has the most similar feel to the Glycerin due to the similar drop as well as the soft forefoot. Heels are both soft but not extremely stable which makes them slightly more flexible than these other two options. The forefoot cushioning and fit of the Phantom are very similar but with a much more aggressive arch and wider toe box distinctly separates itself from the Glycerin. The Vortice has a very comparable ride as well, with a firm yet soft cushioning. I still find the Glycerin 21 to be more responsive than all of these shoes due to the light and cushioned ride.

Well, I would say I feel pretty qualified to talk about this shoe due to my love for the previous model. It was my favorite shoe of 2022. Both of these shoes have a ton of similarities, the same foam makes both shoes feel fairly consistent but the 2 more millimeters of stack height added to the Glycerin 21 was a much-needed improvement. The heel of the 21 is significantly curved medially compared to the 20 which makes walking less stable. Making the 20 a more comfortable working/standing shoe. I found the Glycerin 21 to be way more comfortable running than the 20 as well. For the purpose of supporting you for every mile you will be running, I find that the Glycerin 21 nails it.

THE RUNDOWN

Blake: This shoe is for everyone, a great daily shoe for running and walking. The only people I wouldn’t recommend this shoe to would be anyone who severely pronates. But that is where the Glycerin GTS 21 comes into town and fixes the problem. Whether it is long runs or daily runs this shoe will be able to support you through any step you take. I would definitely recommend this shoe, a true testament to Brooks consistent and supportive shoe line. The Glycerin 21 delivers on the promise that you can keep running while reducing the pain in the process.

Get your own pair HERE!

MEET BLAKE

I have worked at the running lab for over 2 years but have been in the shoe industry since 2018. My running journey started with running in high school for about two years and eventually ended up stopping after shin splints became too debilitating. After coming to the Running Lab and learning correct form I have been able to run and have been back running for around 3 years now. My favorite thing about running is being in nature and seeing cool sights that most people are not going out of their way to find. Just in our local area, I have found some beautiful sights and I can’t wait to run around everywhere exploring the world for the rest of my running career. I love to run at Island Lake, Kensington Metroparks, Brighton Recreational Area’s Trails, and downtown Brighton. And lastly, my interest has primarily been in shoes for a very long time. I love shoe design and running shoes have always been a constant ever-growing interest of mine.