The Brooks Glycerin was once the most comfortable running shoe, with its cushioning stack making it stand out. Now, however, many of the best cushioned running shoes have higher stacks and softer foams than Glycerin—and the Brooks Glycerin 21 is relatively light and low-stack for a cushioned shoe. This makes it a more versatile daily training option than many cushioned shoes, and I rate the Glycerin 21 among the best running shoes for those looking for a cushioning shoe that has pop for faster runs.
Brooks Glycerin 21: Price and Availability
The Brooks Glycerin 21 was released in February 2024 and costs $160 in the US and £165 in the UK. That’s the same price as the Glycerin 20 now, although the older shoe originally launched with a UK price of £155. It’s far from cheap, and although many of the best cushioned shoes now cost a similar amount, there are cheaper options like the Puma Magnify Nitro 2 and the Saucony Ride 17.
How I tested this running shoe
I ran 32 miles in the Glycerin 21, using it mostly for easy runs during my marathon training, including a longer run of about 13 miles. I’ve also tested each of the previous six versions of the Brooks Glycerin series, along with the Brooks Ghost Max and Ghost 15, and several other cushioned shoes from other brands.
Design and implementation
The new Glycerin has updated its upper, midsole and outsole. Of these I would say the most important is the 2mm increase in stack height. The Glycerin 21 is 36mm in the heel and 26mm in the forefoot for a 10mm drop, and while it’s only 2mm, the added cushioning is noticeable when running.
The foam used is Brooks’ DNA Loft v3, a nitrogen-infused EVA that offers a good balance of softness and responsiveness. It’s not as squishy as most foams used in cushioned shoes, but it still protects the feet well while being firm and a bit responsive when running at faster paces.
Despite adding more foam, Brooks managed to keep the weight of the shoe down. The Glycerin 21 weighs 10.2oz/290g in a UK size 9, while the Glycerin 20 is 11oz/314g in the same size. Part of that is due to the redesigned upper, which Brooks describes as more streamlined, but still has plenty of padding around the tongue and collar to provide the high-level comfort you’ve come to expect from the Glycerin line. The shoe fit well in my usual running shoe size, the same one I had used for previous versions of the Glycerin.
There’s a new RoadTack rubber outsole on the shoe, which has more exposed foam on the bottom than the Glycerin 20, but all key impact areas are covered with a thick layer of this rubber, and it held up well in wet conditions.
Running performance
I’ve long been a fan of the Glycerin as a comfortable shoe for easy runs and the Glycerin 20 surpassed that thanks to the introduction of DNA Loft v3 nitrogen-infused foam, which made the shoe more flexible and enjoyable for faster running. . The Glycerin 21 continues on this path by being lighter than the 20 while adding more foam, which increases its comfort. The ride isn’t particularly flexible or as soft as other cushioned shoes, but it’s well balanced and works for a range of runs.
It’s still a shoe that’s best for easy runs and excels especially on long runs. As with the Glycerin 20, my favorite runs on the Glycerin 21 were my longest runs, when the foam provided a supple and protective base to work from. The 10mm drop and lack of a large rocker means the ride is traditional and less smooth than most rocker shoes, but the heel-to-toe transition isn’t so quick that your forefoot hits the ground. The Ghost Max is a sleeker option in the Brooks lineup that has a smoother feel, which some runners may prefer.
When I was running faster in the Glycerin 21, it still felt bulky, so I’d use it in a running shoe rotation with faster shoes, but if you prefer a cushioned shoe for all your runs, then it’s a good daily training option. Almost all of my runs in the shoe were in wet conditions, and the grip from the outsole was reliable even when hitting water-flowing hills. The thick rubber layer will also be durable, and the DNA Loft v3 foam has a well-earned reputation for retaining its bounce over hundreds of miles, so you can expect the Glycerin 21 to be a long-lasting shoe.
Is The Brooks Glycerin 21 Worth It?
If you like a daily gym with cushions, the Glycerin 21 is one of the best options. It’s also a great choice for marathon training and running the race itself if you’re not shooting as fast as possible because of the way the foam maintains bounce and comfort over long distances.
If you want the smoothest ride possible, check out the New Balance Fresh Foam X 1080v13 or the Asics Gel-Nimbus 26, although it’s not as flexible as the Glycerin 21 and I prefer its feel for long rides even at easy paces . There are cheaper alternatives that do the same job, such as the Puma Magnify Nitro 2 and Saucony Ride 17, which are cushioned but still flexible shoes. The Puma Velocity Nitro 3 also has a similar level of cushioning to the Glycerin 21 and is lighter and cheaper, although not as comfortable as the Brooks shoe.
For me, the Glycerin 21 is a more enjoyable running shoe at any pace than Brooks’ Ghost 15, which lacks the pop you get from the DNA Loft v3 foam (which will be used in the upcoming Ghost 16). However, the Ghost Max is a good alternative to the Glycerin 21 if you prefer a smoother, rockier ride.
