Brooks Glycerin Flex Review
The Brooks Glycerin Flex is a neutral road running shoe designed to work with the runner’s body, allowing it to function naturally without sacrificing comfort or cushioning. The Brooks Glycerin has always been the brand’s most cushioned road running shoe, and the Glycerin Flex is no exception. However, it is designed to allow the foot to do more of the work rather than relying on the shoe to guide movement.
Brooks has split its road shoes into two main types. Some models use a rocker-shaped midsole to guide the foot back when it touches the ground, helping maintain cadence and encourage a more upright posture. The most cushioned example of this is the Brooks Glycerin Max 2. The Brooks Glycerin 23 offers similar cushioning but without a rocker, requiring more active effort from the runner to generate forward motion.
With the Glycerin Flex, Brooks has taken the Glycerin 23 and made it more flexible, allowing the foot to move more freely without losing cushioning or comfort. The midsole uses Brooks DNA Tuned, a nitrogen-infused foam that is sealed to prevent air escaping or water and dirt entering. This makes the midsole durable and consistent, with a level of bounce that doesn’t diminish over long runs. The foam is arranged in cells, with larger cells in the heel to absorb impact and smaller cells in the forefoot to provide a firmer, more responsive toe-off. The stack height remains generous, with deep flex grooves through the midfoot and additional grooves in the forefoot. This allows the foot to bend more naturally without reducing cushioning.
The result is a shoe that feels cushioned on landing but allows the foot to move freely as you transition to toe-off. This works the foot more, encourages stronger push-off, and leads to a smoother ride. I land more on my midfoot and found that the heel often didn’t touch the ground at all. My posture felt more upright, and my glutes and hamstrings were noticeably more engaged. Running downhill felt more controlled, with reduced impact thanks to the increased flexibility. Cadence felt quicker, which further reduced impact. On uphill sections, the forefoot felt responsive and made me feel light on my feet.
The heel cup is soft and pliable, gripping the heel well while providing good cushioning. The collar is less padded but remains comfortable and moulds well to the foot. The tongue is lightly padded and made from a very soft material. The engineered knit upper is breathable where needed and supportive in key areas. There is an additional lace hole that allows you to secure the heel more effectively using a runner’s knot.The fit is slightly narrower than other Brooks road shoes, and the toe box has a straighter big toe line, which helps promote a stronger toe-off.
The feel of the ride is very different from traditional Brooks road shoes. Historically, many Brooks models have suited heel strikers, with higher drops and stiffer midsoles that pulled me onto my heel. The Glycerin Flex does not do this. The 6mm drop and flexible midfoot allow the foot to land where it wants to, creating a more natural and uninhibited running gait. This natural feel makes the Glycerin Flex more versatile than just a cushioned training shoe. While designed for everyday running and long runs, it doesn’t feel too soft or sluggish when running at quicker paces. I found it comfortable for steady runs as well as pick-ups during longer efforts.
In terms of sizing, Brooks shoes are similar in length to 361, Topo, Altra, Scott, and Saucony. If you normally run in Hoka, New Balance, Inov-8, or La Sportiva, we would suggest trying half a UK size smaller for a similar length.
In summary, the Brooks Glycerin Flex doesn’t feel like a traditional Brooks running shoe. It offers a more natural, flexible ride while retaining the cushioning and comfort that the Glycerin range is known for.
Alternatives to Brooks Glycerin Max
Altra Fw Via 2: Not as flexible as the Glycerin Flex but, the broad rounded toe box does allow the feet the space to spread and function inside the shoes. If you are used to running shoes with a broad rounded midsole then you are likely to find the quite narrow fit of the Glycerin Flex a bit restrictive. https://www.northernrunner.com/blog/altra-fwd-via-2-review/
Inov-8 Roadfly Max: A broad rounded toe box allows room for the feet to spread and function inside the shoes. Available in two width Men’s and Women’s. Noticeably stiffer through the midfoot particularly when new. The ride is much firmer which does give the feet a bit more stimulation to function but, doesn’t have the same plush feel to the ride as the Glycerin Flex. https://www.northernrunner.com/blog/inov-8-roadfly-max-review/
Topo Phantom 4: A broad rounded toe box with a bouncy feel to the midsole. https://www.northernrunner.com/blog/topo-athletic-phantom-4-review/
Altra Experience Flow 2: A very flexible midsole together with a broad rounded toe box allows the feet to function naturally. https://www.northernrunner.com/blog/altra-experience-flow-2-review/
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