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]

Xero HFS II Review: Keeping Minimalism Alive
By Matthew Klein

In a world of maximal stack height shoes, including those pushing 50 mm, Xero Shoes have continued as one of the few holding on to barefoot/minimalist footwear principles. The first HFS (Highly Flexible Shoe) was a unique, highly flexible, durable road-specific minimalist shoe that provided just enough protection balanced with a high level of ground feel. While a fantastic minimal/barefoot-inspired shoe, all things can be improved. The HFS II is the upgraded version, featuring better upper security, a tiny bit more protection underfoot and an outsole that provides better versatility across different terrains. While a small gain in weight (per our measurements) is a trade-off, the upgrades definitely move this shoe forward as it continues to be an excellent choice for minimal all-day wear and running/athletic activities for those looking for a more natural shoe.

Price: $119.99 at Xero Shoes
Weight: 7.4 oz, 209.8 g (men's size 9), 5.9 oz, 167.3 g (women's size 8)                 Measured Weights: 8.8 oz (Men's size 10)
Stack Height: 12 mm / 12 mm with insole (7mm midsole + 1.5 mm non-woven strobel sheet + 3.5 mm removable sockliner) 
Drop: 0 mm
Classification: Minimalist Road Running Shoe


The Xero HFS II is a highly flexible, minimal, barefoot inspire shoe for road and some mild off-road running. A new upper provides solid security through the midfoot with a wider, anatomic toe box and fit. A thin but protective midsole is highly flexible and provides solid ground feel without being too bare bones. A new outsole provides better traction on a great variety of surfaces, making the Xero HFS II a great option for those looking for a minimalist running/training shoe that can handle more than just road running.

: Vivobarefoot Primus Lite III


The Xero HFS II fits me true to size in my normal men's US size 10. Initially they felt slightly short due to the light toe guard, but this sensation went away quickly. The forefoot features a wide, anatomic foot for plenty of toe splay. The midfoot fits normally and I did not have to lace lock or tighten down the laces. The tongue is free-floating, moderately thick and did not slip. The heel fits normally with mild heel collar padding and no heel counter. There is some stitching and material in the heel to give it structure, but those with heel sensitivities will have no issues with this shoe. The security is surprisingly good for a minimal shoe with a wider toebox. The midfoot overlays are thicker than the last version and do a great job of locking the foot down without being overbearing. I have done a variety of activities in this shoe and not had major slippage even when doing lateral movements.

I have run plenty of miles sockless in these and not had any issues. I have not done longer miles sockless, so someone else will have to comment on that. However, for the majority of running and daily activities, the fit of these has been awesome for those wanting an anatomic but secure fit. 


The HFS II is a highly flexible shoe with a minimal ride. There is 9mm of stack height underfoot, which provides a little protection without muting ground feel. This is a little more than the previous version and I have had better experiences dealing with rocks and other hazards, although you will still have to tread carefully. As a barefoot/minimal shoe, there is a 0mm heel drop. This is noticeable but not aggressive like other highly cushioned zero drop shoes due to there being no midsole compression which keeps the drop consistent (which can change the drop of a zero drop shoe depending on where you land). Despite being a minimal shoe, there is still protection that is evident while walking. I have spent 8-10 hour days on hard hospital and university floors with issue or irritation. I have also run on sidewalks and not come away with overly beat-up feet, although I have kept mileage to 1-2 miles max per run (for my body). The midsole flexes in all directions, making for a natural heel transition and forefoot flex. With the minimally inspired design, this shoe is better for shorter miles, walking and other activities like weight lifting. Among minimal shoes, these are more likely to be training/workout shoes rather than racers. The newest version weighs in at 8.8 ounces for my size 10, a 0.8 ounce increase compared to my HFS I. While not a major deal as I do not do speed work in these (I prefer true racing flats), they are still light enough to do a variety of things in. The new outsole does allow additional versatility onto softer surfaces thanks to improved tread. However, those who want a true minimal trail shoe should check out the Xero Scrambler Low (review soon).

As expected with a Xero Shoe, the outsole has zero wear after 20 miles of running and countless days of walking additional mileage. I had well over 100-200 miles of locomotion in my previous pair (over a year of use) with no wear and expect exactly the same. So those wanting a durable minimal/barefoot-inspired shoe will enjoy the Xero HFS II. 


The Xero HFS II is a minimal shoe with no methods of stability. There are no sidewalls to the shoe, no guidance lines, no specific areas of stiffness and no guidance elements. The one nice thing is that the midfoot is not overly tapered, which provides solid contact with the ground. Even with a 9mm drop midsole, having the midfoot cut out can still feel awkward for those of us who do collapse (and again, pronation is a normal movement and method of shock absorption if you have adequate control of it... like any movement). If you are sensitive to any form of stability or guidance, this is a perfect shoe for your. If you have significant stability needs, this either may not be appropriate for you or will be something to ease into to see if your body can tolerate it. 

Thoughts as a DPT: Evidence-Based Benefits and Who May Benefit from Minimal Shoes
By Matthew Klein

Like the barefoot running craze, there continues to be misinformation regarding the true benefits and risks of running barefoot. There is currently no evidence that suggests running in traditional shoes weakens your feet. There is also no evidence that running in maximalist shoes weakens your feet. They simply encourage you to run in ways that require more muscular work elsewhere and you get used to that. However, there is initial evidence to suggest walking and running in minimalist shoes can increase the size (hypertrophy) of the intrinsic foot muscles beyond normal (Ridge et al., 2018). This does not necessarily mean your feet are weak, but that they will get stronger beyond "normal" because there is more demanded of them in minimalist shoes.

There is also no evidence that suggests there is a higher or lower injury risk in minimalist shoes compared to traditional or even maximalist running shoes (Grier et al., 2016; Malisoux & Theisen, 2020). The injury rates are not different but the types are different. Those who tend to run in minimalist shoes suffer more bone stress-related injuries (stress fractures, etc) and musculotendinous strains of foot/ankle muscles, while those in traditional shoes tend to have injuries more commonly higher up the leg (knee/hip). 

There is also initial evidence that recreational runners who tend to run less may benefit from running in less shoes, while that same protection does not apply to more frequent, higher mileage runners (Malisoux & Theisen, 2020). Those who run less or run infrequently will not experience as much accumulated stress and may be able to tolerate/benefit from this more compared to more frequent runners. 

Our greatest suggestion from this is that these shoes are tools. Different people will be able to tolerate these tools differently. If you have plenty of minimal running experience, have good calf strength, ankle mobility and balance/proprioception, then you will be able to tolerate more minimal running. Most people will benefit from spending some time in a minimal shoe, be it walking or brief running, to improve intrinsic foot strength. How much is necessary to get that benefit will depend on the person. It may be a good idea to spend some time in these shoe types (if you do not have major injuries or issues that prevent you from doing so) if you spend a ton of time in maximalist shoes just to balance out what areas of your body are used to working most. This does not necessarily mean running as walking has been shown to be just as effective. These are tools that different people will be able to tolerate, so understanding how they work, who they might work best for and when they might work best are critical questions to ask about each individual. 


Grier, T., Canham-Chervak, M., Bushman, T., Anderson, M., North, W., & Jones, B. H. (2016). Minimalist running shoes and injury risk among United States army soldiers. The American Journal of Sports Medicine44(6), 1439-1446.

Malisoux, L., & Theisen, D. (2020). Can the “appropriate” footwear prevent injury in leisure-time running? Evidence versus beliefs. Journal of Athletic Training55(12), 1215-1223.

Ridge, S. T., Olsen, M. T., Bruening, D. A., Jurgensmeier, K., Griffin, D., Davis, I. S., & Johnson, A. W. (2018). Walking in minimalist shoes is effective for strengthening foot muscles. 
Faculty Publications. 3159.


The HFS II, like the HFS I, is my go-to all-day shoe. I have enjoyed these for their wider toe box, anatomic fit, solid security and having just enough cushioning while maintaining a high level of flexibility. The durability is awesome and the level of flexibility is exactly what I would want in a minimal shoe. The improved midfoot security is also a great step in the right direction and as mentioned I have had zero issues during movements in a variety of planes of motion. My only major gripe is the weight. My size 10 weighs 8.8 ounces, up from the 8.0 ounces of the original. I can understand that having a durable shoe requires some weight. The upper, midsole and outsole will last forever on these. If that is the necessary sacrifice for that, then I will accept this. However, this is so much less shoe here than others on the market that still weigh far less, even maximalist racing shoes. So my challenge moving forward with Xero Shoes is to focus on making these lighter. With so little cushioning, weight is the primary factor that will effect running efficiency with these shoes. The lighter you get these, the more truly "minimal" and "barefoot" these will become.


The Xero HFS II is for those who want a barefoot-inspired/minimalist shoe with a highly flexible sole, a little more protection and traction than the previous version and an anatomic that works for running and all day wear. The newest version can handle a greater variety of terrain and gym/athletic activities thanks to an improved outsole and upper security. The improved security does come at a weight cost, although it is still light. This will be a walking/foot strengthening tool for most people while seasoned barefoot/minimal runners will be able to enjoy decent mileage in them. Most people will need to ease into this and work on their ankle mobility, toe mobility, balance and calf strength while transitioning. Others may continue to use this as a great protective tool for barefoot strides and shorter runs. My only challenge to Xero is to think about dropping the weight and the price given how little shoe there is. However, given the durability of both the upper and sole, the trade-off and price might be worth it. 


Fit: A- (True to size although initially felt short, anatomic fit. Improved midfoot security and solid lockdown)
B (Rationale for grade)
Stability: N/A (Not applicable as this is a barefoot/minimalist shoe)
DPT/Footwear Science: B (Nothing major or earth-shattering. Continues to be a highly durable minimalist shoe. A little disappointed with weight gain for a shoe with so little there.)
Personal: A- (Like the last version, still my go to for non-running activities. Careful practice has allowed me more frequent miles in these, but not something I can tolerate longer mileage in)
Overall: B+/A- 


Price: $119.99 at Xero Shoes

Shop Men | Shop Women

Check out Gear We Love

*Using the following links to purchase helps support Doctors of Running. Thanks so much!

Ultraspire Fitted Race Belt: The best way to carry your phone and goods on the run. No bounce and various sizes for waist. (Also recommend the Naked belt)
Saysky Running Gear: We were really taken aback by this Scandinavian company's ultra-thin, durable performance clothing
Skratch Recovery, Coffee Flavor: Mental and physical boost post run. Coffee flavor is excellent and goes great straight into a fresh brewed cup
goodr Sunglases: Run in style with goodr's super fun sunglasses.
Feetures Socks: Massively grippy socks that will make you feel more one with the shoe
Amphipod Hydraform Handheld Water Bottle: Perfect for long runs when you need hydration in the summer
Trigger Point Foam Roller: Help get those knots out post-run and feel better for tomorrow
Ciele Hat: Our team's favorite running hat of choice!
Fractel Hats: Our team's wider fitting running hat of choice!


Hoka Gaviota 5 - Hoka moves to a new H-Frame stability that universalizes the Gaviota
Monday Shakeout: The Importance of Heel Bevels in Shoe Design
Adidas Prime X 2 Strung - Adidas stablizes the 50mm trainer greatly for a universal experience
Hoka Stinson 7 - A crossover max cushion shoe that is built for trails, but can do road as well
Puma Magnify Nitro 2 - A higher stack of NITRO and a flatter geometry highlight this max trainer
Monday Shakeout: Low vs. High Drop Shoes
Nike InfinityRN 4 - ReactX highlights a big change to the shoe, along with deconstructing past models

Find all Shoe Reviews at Doctors of Running here.

Thanks for reading!


Facebook: Doctors of Running
Youtube Channel: Doctors of Running
Instagram: @doctorsofrunning
LinkedIn: Doctors of Running
Strava: Doctors of Running
Podcast: Virtual Roundtable
Pinterest: Doctors of Running


Check out the Doctors of Running Podcast to find more reviews, interviews, and running features from the team.

Visit our Podcast Page
Find us on Apple
Find us on Spotify

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.

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

Hoka Gaviota 5

Bottom Ad [Post Page]

// ]]>