Puma Liberate Nitro 2: teaser
By Matthew Klein
Puma Liberate Nitro 2Price: $120 at Running Warehouse
Weight: 6.5 oz, 184 g (men's size 9), (size unavailable in women's)
Stack Height: 28mm / 20 mm
Drop: 8 mm
Classification: Lightweight Minimal Trainer
RUNNING SHOE SUMMARY
The Puma Liberate Nitro 2 is a minimal lightweight trainer/simple workout shoe for those who want more ground feel and flexibility from their shoes. The upper provides a low-volume but comfortable fit that is reminiscent of minimal shoes of the past. The midsole is full-length Nitro foam that not only sits as a lower stack height but also compresses well to provide decent ground feel. Some heel slippage requires some re-lacing, but the Puma Liberate Nitro 2 provides some mild cushioning for those who want a light, comfortable easy day shoe for foot strengthening or to take a break from the super stack norms of the footwear industry.
SIMILAR SHOES: ASICS Hyperspeed 2
PAST MODEL: Puma Liberate Nitro
FIT
The Puma Liberate Nitro 2 fits me true to size in my normal men's US size 10. The volume is low, especially at the forefoot and the width is fairly normal for a lightweight trainer. The forefoot mesh has some stretch to it but fits normal. I was surprised as it look more snug but there was decent room for my toes. The midfoot fits normally with a thin gusseted tongue. There are additional internal reinforcements in the midfoot for lockdown. However, I did not find these to offset the wider, loose heel. I have had a ton of heel slippage in this shoe. There is a highly flexible, small heel counter at the posterior aspect of the rearfoot. I did not notice it at all and those sensitive to counters will do great in this shoe. There are two small pads on the medial and lateral sides of the heel, but the heel collar is mostly thin like the rest of the upper.
Even with lace locking the shoe, my heel slipped. This limited this shoe to easy efforts as anything faster started creating a ton of movement in the rear of the shoe. When I attempted to run sockless in these, it only took two miles to rip the skin clear off my heel bone (had to stop and walk home to put socks on). For that reason, socks are a must with this shoe. The security at the rest of the shoe is decent but be ready for some movement in the heel.
PERFORMANCE
The Puma Liberate Nitro 2 is a minimal lightweight trainer (by today's standards) with a relatively lower stack height and flexible ride. There is 28 mm of Nitro foam in the heel and 20 mm in the forefoot. However, while this foam is softer and compresses significantly which provides decent good ground feel. This is certainly not a minimal shoe like Xero shoes, but the foam compresses enough to get you close to the ground. This creates a softer, but grounded feel at easier paces and a firmer ride at faster paces.
The heel is a little clunky at first due to Puma's classic slightly medially biased bevel. The extra lateral flare at the heel makes for a slappy heel strike, thus landing forward feels more comfortable. This is offset by the amount of softer foam underfoot and the flexible ride. Once past the heel, the shoe transitions forward with a flexible and easy feel. There is a mild forefoot rocker up front that is mostly flattened when standing. Those who like flexibility and mild softness will love the front of this shoe. There is an 8mm heel drop listed but the Liberate Nitro 2 feels far lower. My calf muscles have felt a bit strained in this shoe until they warm up and it feels like it is under 4 mm (which is probably due to me compressing the rearfoot foam so much being a heavy heel striker).
Purpose-wise the Liberate Nitro 2 works best as a foot-strengthening tool during easy runs and may work for some workouts on the track. I initially thought this shoe could handle workouts after some 800s on the track, but that was due to the softer track surface. On road, the Nitro foam bottoms out at faster paces and the shoe ends up feeling somewhat harsh. The ASICS Hyperspeed is a better option given the snappy resilient midsole foam, whereas the Nitro foam is more compliant and doesn't bounce back well. Thus, it works great as a minimal lightweight trainer and can handle track speed stuff but would not be my first choice for the latter.
In line with being more of a trainer, the durability has been quite good. I have over 20 miles on my pair and have almost no wear in my usual spots (posterior lateral heel). I expect an above-average number of miles out of these for a more minimal shoe, but average for a lightweight trainer.
STABILITY
The Puma Liberate Nitro 2 is a neutral, flexible shoe. There are sidewalls on the medial and lateral sides of the midfoot, but these are not super noticeable due to how soft the nitro foam is. There is a small heel stabilizer plate, although this is offset by the extra lateral heel flare mentioned above. This causes some slappiness and medial bias at the heel upon landing. The midfoot is neutral and transitions into a forefoot with sole flare on both the medial and lateral sides of the foot. The lateral sole flare is more prominent, which does tend to push a tiny bit medial. The amount of flexibility in this moves the work and mobility requirements all to your feet. If you need a tiny bit of guidance medially at the heel and forefoot, this shoe may work for you.
Thoughts as a DPT: Requirements of Running in Minimal Flexible Shoes
By Matthew Klein
Many people tend to gravitate toward maximal shoes as the initial perception is often that the higher cushioned rides are more comfortable. They may also feel that the rockers make running easier as these shoes tend to redirect necessary muscular forces required for forward propulsion away from the ankle and up toward the hips and knees. It is known that minimal shoes require more out of the musculoskeletal system for both shock absorption and propulsion than higher stack height shoes. Weight used to be a major difference between these shoe types, but recently the gap is closing with high-stack shoes coming in amazingly light for their sizes (Superblast, Vaporfly 3, Endorphin Elite, etc).
- Normal dorsiflexion (ankle motion) required for gait is 20 degrees. Most people do not have this and it is offset by a little heel drop. A lower drop shoe (or one that compresses and feels lower drop) will require more ankle motion and thus adequate range of motion. Ensuring your calves have enough flexibility and your ankle joint moves enough is important.
- Another spot that needs mobility is your 1st toe joint (aka metatarsophalangeal joint). Normal extension (toe goes up toward the ceiling) for this joint is 60 degrees for walking but can be even greater for the demands of running. Ensuring you have enough mobility at this joint is important as minimal shoes will not have enough of a forefoot rocker to help you if you do not.
- Calf endurance is key given that minimal shoes tend to load the calf muscles more during running. The traditional manual muscle test taught to DPT students is that individual should be able to do 25 full range of motion single leg heel raises at a consistent tempo on both sides. While this may not be enough for faster running, it is a good starting point for easing into these shoes.
- Finally, good single-leg balance is key given that minimal shoes will not provide as much stability or guidance compared to traditional shoes. Working on being able to balance for AT LEAST 30 seconds with your eyes closed will demonstrate solid balance and proprioception.
While smart training and allowing your body to adapt to the stress of this is most important, working on the above will only help ease your transition into this footwear type if you are interested.
Sources:
Ridge, S., Olsen, M., Bruening, D., Jurgensmeier, K. Griffin, D. Davis, I, & Johnson, A. (2018). Walking in Minimalist Shoes Is Effective for Strengthening Foot Muscles. Faculty Publications. 3159. https://scholarsarchive.byu.edu/facpub/3159
RECOMMENDATIONS
I had high hopes that the Liberate Nitro 2 could a faster lighter shoe for me like the Hyperspeed, but it sits more on the training side of this category. I attribute this to the foam being soft/compliant enough that it bottoms out instead of being snappy and resilient. Increasing the foam durometer a little may help with this. While this is a minimal shoe and the softer foam offsets this a bit, I really want Puma to consider fixing their heel bevel placement. Angling that bevel just a little more lateral will do wonders for smoothing out the heel transitions of their shoes (I believe in you Puma, you can do this).
Finally, some drastic changes need to happen with the heel. I suggest either increasing the size of the foam pads underneath the heel collar or moving them up higher. David is going to make fun of me for saying this (since I normally call for less structure in heels) but I think more structure is needed here from a lock down perspective. This does not have to come from a counter, but some additional PWRTAPE may be helpful here or in the posterior midfoot to help create a little more structure. I doubt that will be enough, but PWRTAPE has surprised me every time so there is potential (I'm probably completely wrong on this design suggestion...). Regardless the heel definitely needs better lockdown as the remainder of the inner liner of the shoe is extremely comfortable and has so much potential as a great sockless shoe if it wasn't for this massive flaw.
WHO THIS SHOE IS FOR
The Puma Liberate Nitro 2 is for those who want a slightly softer, lower-to-the-ground, flexible lightweight trainer. The upper fits comfortably through the forefoot and midfoot but features a slipping heel. Those who have wider heels will do well here while others will need to figure out how to lock down the heel. The midsole is comfortable and will work for those who want a shoe closer to the ground that still has some softness. It will work best for those looking for an easy-pace shoe for the road and maybe some non-spike uptempo work on the track. The ride is a bit relaxed so will work better for foot strengthening shorter efforts and strides on track/grass.
I think Puma needs to be more aggressive with this shoe. It gained weight from the previous version unnecessarily. Given there are super shoes that weigh 6.5 ounces (Vaporfly 3 and almost the Fast-FWD), I think this shoe would make more of a mark if it was lower stack. It doesn't differentiate itself much specification-wise and for $120 bucks I would expect more shoe or a better lockdown. It sits better in the $80-100 range with its design. I think there is great potential here, but Puma needs to take a leap and really drop the stack height and stack height. A sub 6 oz shoe would position it to compete better with a shoes like the Saucony Sinister. That market is small enough that it could make an impact there. Currently, it may sit in an interesting spot for those wanting a soft ride but not a max stack height. This differentiates it well from the ASICS Hyperspeed 2 which is a firmer and far faster shoe. This group of shoes is still super small but the Liberate Nitro 2 does help maintain the category for those interested.
GRADING
Matt
Fit: B/B- (Minimal, comfortable upper with loose heel)
Performance: B (Minimal lightweight flexible training shoe and workout shoe on the track. Bottoms out and not fast/snappy for road)
Stability: B [Neutral] (Fairly neutral shoe with some mild medial bias due to extra lateral sole flare at heel/forefoot)
DPT/Footwear Science: B- (Standard minimal lightweight shoe. Midsole bottoming out and lateral flare could be better. Heel slippage and lack of security disappointing)
Personal: B- (Decent comfortable easy day shoe but not snappy enough for what I want in a faster lighter shoe. Heel slippage also a major turn off)
Overall: B/B-
SHOP | SUPPORT DORPrice: $120 at Running Warehouse
Puma Liberate Nitro 2
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