Physical Therapists Using Clinical Analysis To Discuss The Art And Science Behind Running and The Stuff We Put On Our Feet

Post Page Advertisement [Top]

PUMA Eternity Nitro Review
Review by Nathan Brown

The PUMA Nitro Line has worked to cover all of its bases, ranging from the race day ready Deviate Nitro Elite all the way to what we are reviewing today -- the Eternity Nitro. Consistent with all the models in this line, this shoe sports the Nitro midsole and some other features found in other models such as the TPU heel piece. The Eternity Nitro is touted as the stability shoe of the line, and today we will talk about how stable it really is. 

Specifications (per PUMA)
Weight:  9.6oz/273g (men's size 9); 8.0oz (women's size 7)
Stack Heights: 34mm (heel)/25mm (forefoot); including sock liner
Drop: 9mm (7mm without sock liner)
Classification: Stability trainer


The Eternity Nitro is PUMA's take on a stability trainer that sports reinforced side walls (called runGUIDE) instead of traditional posting to attempt to achieve some guidance for the runner. This is a larger fitting, soft shoe with a thicker upper that has a unique lacing system compared to the other shoes in the Nitro line.


Like a few of the other shoes in the Nitro line, the Eternity Nitro fits long. However, the Eternity also fits wide and therefore I would consider going down a half size (maybe even a full size depending on who you are and how you like the fit). Overall, the upper gives off a "premium trainer" vibe similar to what you'd see in the Mizuno Wave Horizon 4 or Saucony Hurricane 23 (but at a lower price point). It is a thick engineered mesh that isn't the most breathable, and I would often finish my runs with wet socks due to sweating. The heel counter is very thick and soft with a lot of cushioning, but the tongue is a thin layer of material similar to what we saw in the PUMA Velocity Nitro. Finally, the lacing system has what PUMA calls "OPTIFIT", which are thicker straps of material that surround the midfoot. These allow for synching up the lacing around the midfoot and actually works rather well to lock the heel into place even with the amount of padding and extra room I had in the shoe. As for comfort, the upper is soft and accommodating and there weren't any hot spots or areas that rubbed. 


I did all of my testing in the Eternity Nitro prior to seeing the specs. If I were to have given my best guess, I would have said a 10.5-11oz shoe with a 8-10mm drop. But surprisingly, this thing only comes in at 9.6oz (7mm drop). The thicker upper, really soft and pillowy platform, and larger feeling fit made this shoe feel heavier than it really is. That said, feeling heavier isn't necessarily a terrible thing. This shoe performed best for recovery runs and had just enough bounce for some daily miles as well for me. The bounce I got from the Eternity was not as much as I got from the Velocity or Liberate, likely due to the higher amount of NITRO foam that you can sink into in this model. 

This shoe has a very soft landing as well as toe off. There are many models I've tested where the heel is soft and then it transitions to a firmer toe, but this keeps it softness throughout. Given the softness in the forefoot, it was really nice for slower and casual paces, but made it harder to push into the foam to pick up the tempo. Like the rest of the NITRO line, the grip is good on all surfaces, wet or dry. 

When running, I did not feel the effects of any of the formal stability elements. The Eternity ran more like a soft, premium daily trainer than a stability shoe.


This is PUMA's stability model. That said, we at Doctors of Running always talk about stability regardless of the category of shoe because there are neutral shoes that are stable and stability shoes that are unstable. Simply putting in posts or sidewalls or widening ground contact doesn't automatically make a shoe stable. A perfect example of this is the New Balance Prism. While not a bad shoe, it simply isn't very stable. It has a very (VERY) soft FuelCell platform with a small and mild dual density post as the main mechanism for stability. There is enough about that shoe (midsole density, narrow outsole contact, etc) that make it unstable for a number of folks. 

The reason I bring up the Prism is because there are some things that are analogous to the PUMA Eternity, though the Eternity is certainly more stable and integrates a few more stability elements. The primary similarity is how soft the footbed and midsole is. The thick slab of NITRO foam is going to have a lot of pillowy-softness, which we know gives inherent demand for stability from the foot, including the foot intrinsic musculature. In addition to that, the main component stabilizing the foot within the midsole itself is the runGUIDE technology (reinforced side walls) that didn't really interact with my foot. This was likely due to the wider fit and possibly due to how much "give" is present in the midsole. I'm surprised that PUMA didn't integrate the denser heel cup in the lower part of the midsole like what found in the Velocity. I could see how having a heel cup would help center the foot on the platform during heel strike. In summary, the runGUIDE technology will give a very mild amount of guidance to the foot, which may work really well for some, but will not be enough for those who know they need a lot more structure.

However, where the Eternity does well is modifying other elements of the shoe to provide some stability. The first is the outsole contact with the ground. Compared to the other models, the outsole in the heel, midfoot, and forefoot has a significantly wider ground contact, providing a more inherently stable platform. Secondly, the upper stability through the OPTIFIT does a great job holding the foot on the platform despite the larger fit. These two things do well to offset the instability introduced through a soft midsole. 

When it comes down to it, the Eternity runs more like a slightly stabilized neutral premium trainer than a true stability shoe. So for those who like soft and pillowy midsoles (Wave Sky, Triumph, etc) but find them too unstable may have luck with the Eternity. Additionally, the high amount of cushion and bit of  stabilization that happens through the wider platform may make this a viable option for those who have rigid arches and/or supinate. There weirdly aren't many shoes out there that are designed specifically for those with supination and rigid arches (which are correlated with injury more consistently than even with excessive pronation). These shoes provide the cushion and base that may be appropriate for those with supination and doesn't have any posting or invasive structure on the medial side that would be detrimental to those with high, rigid arches.


I think it would be interesting to see how the stability of this shoe is improved with the addition of the heel cup found in the Velocity (though this may have  been played with during production and just didn't work out...who knows). Additionally, I think the upper could be stripped down quite a bit, either by simply thinning it or by adding more slats for air in the upper. Finally, I think that the fit was just too big, so bringing it down a bit in length would help make it more true to size. 


The PUMA Eternity is for people who prefer a soft shoe from heel to toe and who don't have significant stability needs. It may be a viable option for those with a rigid arch given the softer cushion. It functions best if looking for a shoe for casual running, recovery runs, and daily miles for some. 

GRADING (Category: Stability)

Fit: C+ (Fits wide and long, too thick in the upper, but lacing system works well)                     
Performance:  (Soft pillowy ride, good for recovery miles, runs heavier than it is, hard to push off toe quickly) 
Stability: B- (For a stability shoe, not really that stable given the soft platform) 
DPT/Footwear Science: (Higher score for the wider platform and lacing system, side wall not intrusive, cushion may be good for those with supination) 
Personal: (Too soft and fit way off for me, upper too thick)    
Overall:  B-     

Find the Eternity Nitro at Puma here.



Compare Mild Stability Trainers
New Balance FuelCell Prism
- Extremely mild stability neutral runners will even take to thanks to FuelCell foam
Nike Structure 23 - Gone from past form, the Structure 23 utilizes a wide base to bring stability
On Cloudflyer - Similar to the Structure, On employs geometry to help provide stability while also providing a firm ride for those not seeking high volumes of cushioning
Asics Kayano Lite - One of the best modern stability shoes, providing a mix of nontraditional elements to reinvent the Kayano series

Recently at Doctors of Running
Saucony Endorphin Speed 2 vs. Pro 2
Hoka Clifton 8 Review
- The brand's signature trainer returns
Coach Dave Ames on Holistic Training, Tapering, and Rest | Podcast
Inov-8 Trailfly Ultra G 300 Max Review - Supercharged with graphene, an ultra-strong material, the shoe is built to last longer and take you farther on trails
Asics Novablast 2 - Stability changes to the heel help bring this neutral trainer favorite to life for more runners than ever before

Thanks for reading!


Dr. Matthew Klein is a 150 lb male with notable PRs of 14:45 for 5k and 2:32:44 for the full marathon.  He typically runs 70-100 miles per week and trains at a variety of paces from 8min per mile recovery runs to 4:40 per mile 1k repeats.  He prefers firmer and responsive shoes with snug heels and medium to wide toe boxes.  The stability guy of the group, he also prefers a little stability in his footwear. However, as a researcher, clinician and running shoe aficionado, he will run in anything. IG handle @kleinrunsdpt

Dr. David Salas is a 135 lb male with notable PRs ranging from 3:54 in the 1500m to 1:08:36 for half marathon. He typically runs 60 to 70 miles per week and trains from about 7:30 recovery runs to fast shorter efforts at 4:30 pace. He normally prefers neutral shoes with a firmer ride, but is completely open to other types of shoes.  He is a footwear enthusiast at heart and will always appreciate a high quality shoe when it comes around. For updates on training or testing, IG handle: @docsofrundavid

Dr. Brown is a 155 lb male with notable PRs of 18:18 5K, 39:25 10K, 1:29:01 half marathon, and 3:54 marathon. He typically runs between 20-40 miles per week at a variety of paces from 7:30-8:30 min/mile for recovery runs to 6-6:45 min/mile for tempo runs. He typically prefers shoes that provide some cushioning underfoot but still maintain a more firm and responsive feel. Current goals for 2020 are to break the 1.5 hour half marathon and 3:30 marathon. IG handle: @nate.docsofrunning

Editor's Note: As always, the views presented on this website belong to myself or the selected few who contribute to these posts. This website should not and does not serve as a replacement for seeking medical care. If you are currently injured or concerned about an injury, please see your local running physical therapist. If you are in the Los Angeles area, I am currently taking clients for running evaluations.

Doctor of Physical Therapy
Board Certified Orthopedic Clinical Specialist
Fellow of the American Academy of Orthopedic Manual Physical Therapists

Nathan Brown PT DPT MS
Doctor of Physical Therapy 
Masters in Anatomy and Clinical Health Science
Movement Performance Institute Certified in Advanced Functional Biomechanics 

David Salas PT DPT CSCS
Doctor of Physical Therapy
Certified Strength and Conditioning Specialist

Bach Pham MS
Marketing and Social Media Manager
Master of Arts in Cultural Anthropology

***Disclaimer: These shoes were provided free of charge in exchange for a review.  We thank the  people at *** 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 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.

Like and Follow Doctors of Running
Facebook: Doctors of Running Youtube Channel: Doctors of Running 

Please feel free to reach out, comment and ask questions!

Bottom Ad [Post Page]

// ]]>