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Brooks Glycerin GTS 20 Review: Softer Stability
By Chief Editor/Founder Matthew Klein

The Brooks Glycerin series has been a staple premium cushioned series for a long time. Past runners may know of the Glycerin GTS as the Transcend, before Brooks renamed their line to help simplify things. The Brooks Glycerin GTS is an expansion of the successful Glycerin series that allows for a single shoe to possess a variety of options depending on the individual's needs. Whether it be neutral, guidance/stability, or a thicker or lighter upper (Stealthfit). A true example of Brooks trying to apply their "Run Signature" program to their footwear, the GTS version allows for those with stability needs to experience the Glycerin without making an entirely new and complicated shoe. 

Price: $159.95 at Running Warehouse
Weight: 10.5 oz, 298 g (men's size 9), 9.4 oz, 266g  (women's size 8)
Stack Height: Not Provided
Drop: 10 mm
Classification: Premium Cushioned High Stability Training Shoe



RUNNING SHOE SUMMARY

The Brooks Glycerin GTS 20 is a premium, highly cushioned stability shoe for daily training and easy miles. It features a new midsole called DNA Loft v3 (nitro-infused foam), providing a cushioned ride throughout the length of the shoe. The posterior heel flare makes for a clunky rearfoot, but anyone landing farther forward will be treated to a smooth toe-off. The upper fits true to size with a slightly thicker upper that hugs the foot well. Continuing with the GuideRails on both sides of the shoe, the Brooks Glycerin GTS 20 is for those looking for a stable shoe with some extra cushioning for long and easy mileage.

FIT 


The Brooks Glycerin GTS 20 fits me true to size if slightly short in my normal men's US size 10. There is a fairly normal amount of width throughout the length of the shoe with a little extra room in the forefoot. The fit feels slightly short after putting them on thanks to a tapered toebox, but the upper stretches during the run to provide a secure fit. Those that are between sizes may want to size up however as it almost feels short. The engineered air mesh is slightly thicker but does stretch nicely to accommodate variations around normal width feet. It does not breathe well, so I have found my feet to get warm in the hot Southern California summer months. The inner lining of the upper is seamless (except for the heel/midfoot transition) and I have been able to wear these sockless without issue (it actually made them fit better for me). The tongue is thick and while it does intertwine with the laces, can slip a bit if not locked down before the run. The laces interact well with the midfoot portion of the upper and can easily be loosened or pulled tight to modify the fit there. The rearfoot features a moderately padded heel collar and counter. The counter is large and stiff, however I have not noticed it thanks to the cushioning between it and my heel. Those sensitive to heel counters should approach this shoe cautiously as it may become more problematic as the shoe breaks in. Overall, this is a comfortable, well-padded, and secure upper that should work well for those who want a more traditional fit.





PERFORMANCE 

The Brooks Glycerin GTS 20 is an easy mileage and traditional training shoe for those who want a moderately soft ride. The new Brooks DNA Loft v3 midsole is a nitrogen-infused midsole that provides a softer initial feel that begins to firm up. Combined with the Ortholite midsole, the initial step in feel is soft and cushioned. The midsole is not bouncy at all. This is more noticeable in the rear of this shoe as the guide rails and medial post in this shoe provide a little more firmness in the heel and midfoot (compared to the normal Glycerin 20). The DNA Loft v3 began to firm up after 25 miles, providing a stable, more mildly soft and highly cushioned ride. This is not a responsive shoe, but one that is best for when you are plodding along. The weight is definitely noticeable at 10.5 ounces (>11 ounce in my size 10) and is not meant for faster running. There is a 10mm heel drop (stack heights were not provided) but it feels higher than that. This is due to the posterior heel flare which makes the rearfoot clunky upon landing. There is small heel bevel, but this does not offset that clunkiness. The midfoot and forefoot are far smoother thanks to the solid forefoot rocker at the front. There is only a little flexibility up front despite some flex grooves, but this is well compensated for by the rocker up front. 

Durability is a strong suit of this shoe as I have not been able to even dent the outsole after 30 miles. The midsole has firmed up at 30 miles, but remained consistent after 20 miles. The smooth outsole makes this best for road use with mild tail use (I would suggest a true trail shoe for more aggressive trails). This further demonstrates that this shoe is a daily training and mileage workhorse shoe for those who want a cushioned ride with some guidance for easier paces. 





STABILITY 

The Brooks Glycerin GTS 20 is a higher-level stability shoe, especially for those wanting some guidance in the heel and midfoot. Elevated midsole sidewalls, ie GuideRails sit on both the lateral and medial side of the sole. These are noticeable in that my heel feels centered regardless of where or how I land. The medial side is longer and denser, extending into the midfoot helping to continue to guide the foot forward there. There are integrated well into the midsole, but add additional stiffness to both the heel and midfoot. The harder you land or deviate, the more noticeable they become. The sole is also designed to be inherently stable. The full ground contact outsole provides a solid amount of contact. The midfoot is filled in more than other shoes and the entire length of the shoe has some solid sole flare, particularly in the heel and midfoot. Overall, the Brooks Glycerin GTS 20 is a higher-level, cushioned stability shoe for those who want a traditional ride with some new age, but significant stability methods in the rearfoot and midfoot.

THOUGHTS AS A DPT / FOOTWEAR SCIENCE

Posterior Heel Flares

The Brooks Glycerin GTS 20 and Glycerin 20 both feature posterior heel flare, which is where the midsole/sole extends behind the heel. While this may look interesting from an aesthetic standpoint, it adds some unnecessary work and stress to the anterior structures of the lower leg. Having a posterior heel flare means that a heel striker will likely hit the ground earlier than expected. Prior to landing, the muscles in our legs responsible for shock absorption (Quadriceps, gluteals, anterior tibialis, etc) begin to turn on in preparation to work. Hitting the ground early means that impact will occur prior to these muscles being completely ready. Additionally, this also means that the front of the foot has a longer distance to travel to get to the ground at the same speed. This means a great eccentric load on the shin muscles (anterior tibialis being one of them) as the body has to work harder to control this motion.

The research on posterior heel flare in running is limited. One study demonstrated that while not statically significant, a posterior heel flare did increase muscle activation of the anterior tibialis (Queen, 2004). The largest finding was that different runners use different strategies to get around this, which is fairly normal for the variability seen in movement patterns among human beings. However, that variability may not be enough to decrease the stress seen on the anterior structures of the lower leg. The evidence on walking suggests that a posterior heel flare can improve postural stability in older adults while walking (Menz & Lord, 1999). This may be due to the resistance to posterior motion and their shorter step length and reduced dorsiflexion may facilitate forward progression. Further evidence has suggested that both beveled and posterior heel flares can reduce overall loading rates with walking (Daryabor et al., 2016). However, beveled heels reduce the first impact peak compared to normal and posterior heel flares, the latter of which has a much larger impact at that point (the initial shock of landing).


A beveled or curved heel (that sits under the heel rather than behind it) acts to facilitate the natural rocker that is your curved heel bone (heel rocker). This helps us efficiently roll forward during walking and running gait (when people used to perform gait while barefoot). Some of the above research did find that a posterior heel flare did increase the transition speed of heel strike in certain people (not everyone), but that was due to it being forced rather than facilitated. This may not be a good thing, as forcing motion faster means increased eccentric load, which is the most stress you can place on muscles, tendons and other tissues (more stress means more potential for injury if not prepared). If someone has adequate strength and control of the shock-absorbing muscles, this may be ok. Most people, especially newer runners, will not have that control, strength or conditioning, potentially placing them at risk for things like anterior tibialis tendinitis/strains (Shin Splits) and/or anterior compartment syndrome (rare).

With over 90% of the running population being heel strikers (and at least 70% of elite runners doing the same), a well-beveled heel, rather than a posterior heel flare, may be beneficial to ease heel transitions, especially among new runners getting used to controlling the motions of running (Anderson et al., 2017; Kasmer et al., 2013).

However, for a walking shoe, a posterior heel flare may be beneficial for certain people, particularly older individuals, to facilitate improved gait speed, postural stability and reduce loading rates.

References

Anderson, L., Barton, C., & Bonanno, D. (2017). The effect of foot strike pattern during running on biomechanics, injury and performance: A systematic review and meta-analysis. Journal of Science and Medicine in Sport20, e54.

Daryabor, A., Saeedi, H., Ghasemi, M. S., Yazdani, M., Kamali, M., Nabavi, H., ... & Amini, N. (2016). Influence of heel design in an orthopedic shoe on ground reaction forces during walking. 
Prosthetics and orthotics international40(5), 598-605.

Kasmer, M. E., Liu, X. C., Roberts, K. G., & Valadao, J. M. (2013). Foot-strike pattern and performance in a marathon. 
International Journal of Sports Physiology and Performance8(3), 286–292. https://doi.org/10.1123/ijspp.8.3.286


Menz, H. B., & Lord, S. R. (1999). Footwear and postural stability in older people. 
Journal of the American Podiatric Medical Association89(7), 346-357.

Queen, R. M. (2004). 
The effect of positive posterior heel flare on muscle activation, kinetics, and kinematics during
running gait
. The University of North Carolina at Chapel Hill.






RECOMMENDATIONS

As I am known to recommend and discussed above (so much so that Nathan has suggested we make a shirt that says this), the Brooks Glycerin GTS 20 would benefit from a better heel bevel. I have enjoyed almost every part of this shoe except the clunky rearfoot and believe that correcting the posterior flare with a better bevel may make a far smoother ride. Many newer runners may be looking to try this shoe, having a better transition at the rearfoot may improve their overall transition into running.

The other thing I would recommend is to further develop the DNA Loft v3 midsole. I must admit that I have been underwhelmed by my experience with this material and have found other Nitro midsoles to be superior. This one is cushioned but tends to lack bounciness/responsiveness. There is potential here, so I do want to encourage Brooks to continue to explore this midsole design. While it seems like it will last forever, in today's market, I would expect a little more excitement and bounce (especially for $160).

WHO THIS SHOE IS FOR 


The Brooks Glycerin GTS 20 is for those wanting a mildly soft, cushioned, higher heel drop, stable, normal-fitting, durable shoe for easy running and walking. The upper is comfortable, with a normal width fit except for a slightly wider forefoot and tapered toebox. The full-length DNA Loft v3 is mildly soft, which combined with a large amount of midsole, a flared platform and strong GuideRails makes for a guided/stable ride. There is a posterior heel flare, which creates a clunky rearfoot and the feeling of a higher heel drop. However, this is made up for by a smooth midfoot/forefoot transition. Those who tend to land farther forward or who want a solid rearfoot may enjoy this shoe more. Overall, the Brooks Glycerin GTS 20 continues as a premium stability shoe for those that want more cushioning. Some work still needs to be done to bring the DNA Loft v3 foam to reach its full potential. 



GRADING 

Matt
Fit: A-/B+ (Slightly short due to tapered toebox and thicker material, but comfortable secure fit that can handle sockless running)
Performance: B/
B- (Cushioned ride but lacks responsiveness or bounce. Slightly firmer/clunky heel with smoother forefoot)
Stability: A (Solid stability from heel to midfoot with a wider sole, GuideRails and solid upper lockdown)
DPT/Footwear Science: B+/B (Great maintenance of GuideRail system with a softer shoe, but posterior heel flare makes for clunky ride that may place more stress on anterior structures of the leg)
Personal: C+/B- (I want to like this shoe more, but the clunkiness of the heel ruins this for me. Underwhelming ride overall but may work for someone looking for a traditional feeling shoe with newer level stability)
Overall: B

SHOP | SUPPORT DOR

Price: $159.95 at Running Warehouse

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FURTHER READING

Skechers Persistence - A beginner friendly shoe for daily training, featuring a forefoot H Plate for pop
The Running Retail Episode | DOR Podcast #99
Asics Metaspeed Sky+
- A big update to the super shoe stride racer
Zen Running Club, Made From Good Decisions | DOR Sustainability Project #3
Xtep 160x 3.0 - A narrow, but very fast peba racer for 5k to half marathon
New Balance FuelCell SuperComp Trainer - Brand new massive stacked shoe for long runs
Salomon Phantasm - Lighter, super rockered road shoe

Find all Shoe Reviews at Doctors of Running here.

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***Disclaimer: These shoes were provided free of charge in exchange for a review.  We thank the people at Running Warehouse and Brooks for sending us a pair.  This in no way affected the honesty of this review. 
We systematically put each type of shoe through certain runs prior to review. For trainers and performance trainers, we take them on daily runs, workouts, recovery runs and a long run prior to review (often accumulating anywhere from 20-50 miles in the process). For racing flats we ensure that we have completed intervals, a tempo or steady state run as well as a warm-up and cool down in each pair prior to review. This systematic process is to ensure that we have experience with each shoe in a large variety of conditions to provide expansive and thorough reviews for the public and for companies. Our views are based on our extensive history in the footwear industry and years testing and developing footwear. If you are a footwear rep looking for footwear reviews or consultations on development, we are currently looking to partner with companies to assist, discuss and promote footwear models. Partnership will not affect the honesty of our reviews.

Please feel free to reach out, comment and ask questions!
Contact us at doctorsofrunning@gmail.com

NEXT: The Running Retail Episode, DOR Podacst #99

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